Chapter 3 (TERRA-3): Human Influences on Forest Wildlife Habitat · 2013-12-08 · Chapter 3: Human...

Chapter 3: Human Influences on Forest Wildlife Habitat 63TERRESTRIAL

■ Some wildlife species, particularlyhabitat specialists, have beenharmed by loss and degradationof forest habitat and populationisolation caused by urbanizationand agriculture.

■ Other forest wildlife specieshave benefited from the creationof edge habitat and have adjustedto the new habitats created by people.Habitat generalists tend to adjustmore easily to changes broughtabout by urbanization.

■ Urbanization excludes somesensitive forest wildlife species butincreases the presence of others.Urban habitats vary in their abilityto support a diversity of forestwildlife. Advance planning andcareful management can enhancethe habitat value of urban andsuburban conservation areas.

■ For the most part, wildlife speciesthat are tolerant of urbanizationare not the rare or declining speciesthat are of management concern.

■ For species with area sensitivities,those that require forest interior,those that require specialized habitats,and those intolerant of humandisturbance, special managementconsiderations will be neededas urbanization increases in areasof the South.

■ Prior to European settlement,early successional and disturbance-dependent birds were found innaturally occurring and NativeAmerican-maintained forest openings.Many of these disturbance-maintainedecosystems have been lost from thelandscape during the last 300 years.

■ The value of agricultural areasin providing habitat for earlysuccessional wildlife species (suchas bobwhite) depends largely on howthey are managed. “Clean farming,”loss of pastures, creation of fescue-dominated pastures, and the use ofheavy, fast-moving machinery havereduced the value of the habitatformerly found in pastures andagricultural fencerows.

■ Agricultural crops provide foraginghabitat for some forest wildlife, suchas deer, black bears, raccoons, andmany bird species.

■ Woody fencerows enhance thehabitat value of agricultural areasfor some wildlife and facilitate themovement of other forest wildlifespecies. However, woody fencerowsin grassland habitats can reducethe habitat value to grassland-dependent birds due to increasingpredator presence.

■ Abandoned agricultural fieldsin the South have provided importantold-field habitat for some earlysuccessional and disturbance-dependent wildlife species. Thisabandonment trend is diminishingin many areas of the Southeast, butforecast abandonment of agriculturallands in the Western portion ofthe region may provide at leasta temporary benefit for earlysuccessional species.

■ Successful conservation ofsome forest bird species willlikely require forest managementareas with thousands of acres ofcontiguous forest habitat. Similarly,many early successional anddisturbance-dependent bird speciesare also area-sensitive, requiring

Key Findings

Impacts of Exotic Plantsand Animals■ Exotic plants and animals havehad a documented impact on forestwildlife and habitats. Exotic speciesthreaten the survival of some sensitivewildlife species.

■ Some forest wildlife species havebenefited from exotic species, butindiscriminant use of exotic speciesfor wildlife management purposes inthe past has led to serious problems.

■ Of the exotic species introducedinto this country, only 4 to 19 percenthave caused great harm. Another 6to 53 percent have neutral or asyet undetermined effects.

■ Approximately 42 percent of speciesthat are listed in the United States asthreatened or endangered under theEndangered Species Act are at riskbecause of competition with orpredation by exotic species.

■ More effective programs forpreventing the introduction andestablishment and spread of exoticspecies are needed. Protectionand recovery of native speciesand ecosystems should be includedas a goal in programs for controland management of exotic species.

Land Use Changesin Forested Habitats■ Urban and agricultural landuses have interrupted the continuityof southern forests and createdforest islands. Wildlife speciesdiffer in their response to theresulting fragmentation.

Chapter 3:Human Influences onForest Wildlife Habitat

Kenneth L. GrahamU.S. Fish and Wildlife Service

What are the likely effectsof expanding human

populations,urbanization, and

infrastructuredevelopment on wildlife

and their habitats?

Southern Forest Resource Assessment64

TERRESTRIAL

hundreds of acres for successfulconservation of some grasslandbird species and dozens of acres forsome scrub-shrub birds.

■ The area-sensitivities documentedfor many forest bird species mustbe considered in a landscape context.Forest patch size is of greater concernin fragmented landscapes, such asthe ridge and valley province of theAppalachians and the MississippiAlluvial Plain, than in predominantlyforested landscapes, such as heavilyforested areas of the southern BlueRidge and Cumberland Plateau andthe Ozark-Ouachita Highlands.

Linear Land Uses (Roads,Power Lines, and Trails)■ The effects of linear land uses(roads and utility rights-of-way)on forest birds should be consideredin a landscape context. A continuumof effects has been documented,depending on the percent of thelandscape forested, the road typeand width, the maintenance needs,and other site-specific factors.

■ Linear corridors, such as roadsand power lines, can exclude sensitiveforest wildlife from the adjoininghabitat for distances ranging up to330 feet or more. Effects on sensitiveforest birds are of more concernin fragmented landscapes.

■ In largely forested landscapes,roadsides and power line corridorscan provide important habitat forsome grassland and early successionalbird species with less concern requiredfor the negative effects often attributedto fragmentation.

■ Linear corridors act as barriersto the movement of some wildlifespecies, fragmenting populations.Examples include road effects onwoodland mice, interstate highwayeffects on black bears, and power lineeffects on some neotropical migrants.Negative impacts documented forneotropical migrants as a resultof fragmentation (such as reducedreproductive success in smallforest patches) are of greaterconcern in heavily fragmentedlandscapes, however.

■ Linear corridors act as travel lanesfor other wildlife, such as grasslandor scrub-shrub birds in largelyforested landscapes, connectingisolated areas of habitat.

■ Roadsides and power line corridorsfacilitate the spread of exotic plantsand animals. Many exotics havebeen slower to gain a foothold inpredominately forested landscapes.

■ Road mortality has been welldocumented for many wildlifespecies, but the extent of the problemvaries with a number of parameters,including traffic speed and volume,road type, extent of cleared rights-of-way, wildlife species present, andseason. Road-related mortality is aserious problem for some rare species,such as the endangered Floridapanther and the endangered Key deer.

■ Sensitive forest plant species canbe negatively impacted by human useof forest trails. “Collectable” wildlifemay become rare along trails.

Introduction

Effects of Exotic Specieson Forest Wildlife andWildlife Habitat

Exotic nonnative plants and animalswere introduced into this countryeither intentionally or accidentally.In addition, many native specieshave been accidentally or intentionallyintroduced to other regions of thecountry, sometimes with negativeconsequences. The latter group willnot be discussed in this chapter. SinceEuropean colonization, thousandsof plants and animals have beenintentionally introduced into the UnitedStates. Many of these introductionshave been beneficial to humans.Nonindigenous crops and livestockare the foundation of U.S. agriculture(U.S. Congress, Office of TechnologyAssessment 1993). Other exotic speciesare mainstays of horticulture and thepet and aquarium industries: others areused successfully for soil erosioncontrol and biological control. Of theintroduced species, only a relatively fewcause great harm. The U.S. Congress,Office of Technology Assessment,estimates 4 to 19 percent of exoticspecies fall into this category. Another 6to 53 percent are estimated to haveneutral or unknown effects. Many ofour most invasive exotic species havebeen introduced into an environment inwhich they did not evolve and in somecases they have few or no naturalenemies. Once established, they

reproduce and spread unimpeded by(and often at the expense of) nativeplants and animals.

Human Land Use Changesand Forest Wildlife

Following European settlement,historic trends in southern forestwildlife have closely followed habitatchanges associated with landconversion and timber resourceremoval, coupled with uncontrolledexploitation of many species. For amore detailed history of southern forestwildlife see chapter 1. Alterations inland use have changed the amounts offorest habitat available to forest wildlifespecies. They have fragmented foreststands and changed forest edge andforest interior habitats. Changes inthe abundance, species richness, andspecies composition of forest wildlifehave been documented in responseto land use changes. This sectiondescribes the responses of forestwildlife to human land use changes.

See chapters 6 and 24 for a moredetailed discussion of historic land usechanges. The initial conversion offorests and forest openings to farmlandbrought many changes in the numbersand kinds of wildlife (Bolen andRobinson 1995). Land conversionswere not always negative for wildlife,however. Timber cutting forhomesteads, cooperage, tanbark,heating, and land conversion (for fieldsand livestock) was initially beneficialto many wildlife species (Clark andPelton 1999). Small farms carved fromforests offered more edge habitat andsupplemental food sources for manywildlife species. As forest timberingand land use conversions increased,however, a combination of habitat lossand unrestricted wildlife exploitationdecimated populations of black bears,white-tailed deer, and turkeys (Adams1994, Clark and Pelton 1999).

Later, a trend toward abandonmentof the small farms carved into wood-lands began as the soils were depleted(chapter 6). As previously tilled landsreverted to shrubs and other vegetation,white-tailed deer, eastern cottontails,northern bobwhite, and some earlysuccessional bird species were highlyfavored (Clark and Pelton 1999, Hunterand others 2001b). The conversion ofagricultural land to some type of forestcover is expected to continue in someareas of the South as landowner returns


from agriculture decline relative tothose from forestry (chapter 6).Recent changes in farming practiceshave reduced the value of farms ashabitat for some wildlife species.

Currently, strong economic growthhas led to increased urbanization inparts of the South (chapter 6).Urbanization fragments the naturallandscape, destroys habitat requiredfor many species, modifies habitat forothers, and creates new habitat forsome species (Adams 1994). This landuse shift will continue to influence theregion’s forests along with forest wildlifeand habitat (chapter 6). Recent patternsof urban growth in the South havemoved more people into the historicallyrural areas in low-density residentialdevelopments. In some areas of theSouth, forest cover remains relativelyhigh, but the landscape is highlyfragmented. Land use changes thatresult in increased forest fragmentationcould have negative impacts on anumber of forest wildlife species,including many mature forest andearly successional bird species.

Linear Land Uses (Roads,Power Lines, and Trails)

Along with urbanization, linearhuman land uses, such as roads andpower lines, are increasingly prevalentin the South. The mortality of wildlifedue to vehicle collisions and foresthabitat loss are the most obviousimpacts of roads on forest wildlife,but an increasing body of informationsuggests that the effects on wildlifepopulations are much more complex.About 3.85 million miles of publicroads now exist in the UnitedStates (Forman 2000). Based on anassumption that some of the ecologicaleffects of roads extend outward formore than 330 feet, Forman estimatesthat about one-fifth of the U.S. landarea is directly affected ecologicallyby the system of public roads. Severalcompilations and review papers onthe ecological effects of roads areavailable (Findlay and Bourdages2000, Forman and Deblinger 2000,National Resources Defense Council2000, Trombulak and Frissell 2000).

Similarly, power line corridorsfunction in a variety of ways to affectforest wildlife populations. Knight andKawashima (1993) estimated that therewere more than 0.31 million miles of

power lines in the United States,covering an estimated 5.2 millionacres of land.

Trails also are linear features thatbisect forest habitats and can affectsensitive forest plants and wildlife.Outdoor recreation activities aregrowing in popularity throughout theUnited States (Miller and others 1998),and recreational opportunities in theSouth are increasingly concentratedon the relatively small percentageof forested public land (chapter 11).More information about outdoorrecreation in southern forests canbe found in chapter 11.

Methods

To describe the documented effectsof introduced exotic species, humanland use changes, and infrastructuredevelopment on forest wildlife,information was incorporated fromavailable scientific literature and theWorld Wide Web.

Data Sources

Sources of information used forcompiling this chapter are cited in thetext and details about these referencescan be found in Literature Cited.

Results

Effects of Exotic Specieson Forest Wildlife andWildlife Habitat

Exotic plant pathogens and forestwildlife—More than 20 species ofexotic plant pathogens have beenintroduced into forests in the UnitedStates (Pimentel and others 1999), andexotic forest pests have greatly alteredthe species composition of forestsin the East (Campbell 1997). Sometree species, important as sources oftimber, other products, wildlife food,or other ecological services, have beenvirtually eliminated throughout theirranges or greatly reduced in numbers inlarge portions of their ranges. The lossof nuts and berries formerly producedby vanishing or severely reduced treespecies has had a poorly documentedbut surely substantial impact on wildlifespecies of the forest (Campbell 1997).See chapter 17 for a complete

discussion of forest timber pathogensand diseases. Although the impacts ofexotic plant pathogens to timberresources are well documented, theimpacts on forest wildlife resources arenot well described.

At the beginning of the 1900s, theAmerican chestnut was one of the mostimportant wildlife plants of the EasternUnited States (Martin and others 1951).With this tree practically exterminatedby the exotic chestnut blight, mast-dependent forest wildlife, such aswhite-tailed deer and black bears,had to settle for inconsistent acorn andhickory nut crops as their primary food(Clark and Pelton 1999). The blightalmost certainly reduced the carryingcapacity of southern highland habitatsfor mast-dependent wildlife. Hard mastoutput may have been reduced as muchas 34 percent following the loss ofchestnuts (Diamond and others 2000).The blight is thought to have causedat least five indigenous insect speciesto become extinct or extremely rare(U.S. Congress, Office of TechnologyAssessment 1993). In areas whereresprouting chestnuts remain inthe understory, birds and mammalscontinue to transport virulent andhypovirulent-like strains of chestnutblight fungus (Scharf and DePalma1981). Chinquapins in southern forests(including the Allegheny and Ozarkchinquapins) vary in their susceptibilityto chestnut blight. The chinquapinsmay not match the former value ofthe American chestnut in their habitatcontribution to wildlife in southernforests (Martin and others 1951),but the nuts they produce arevaluable to wildlife (U.S. Depart-ment of Agriculture, Forest Service1999). Chestnut blight has affectedchinquapins in southern forestsand is expected to continue reducingthe prevalence of susceptible treespecies. However, no exterminationof any southern wildlife species hasbeen documented in conjunctionwith chinquapin losses.

Dutch elm disease devastatedAmerican elms as it spread acrossmost of the country. In areas whereDutch elm disease removed the elmtrees from the forest canopy, birdpopulation surveys documented highlocal extirpation and colonization ratesby bird species during the early 1950s(Whitcomb and others 1981). In GreatBritain, reductions in bird abundance


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Table 3.1—Exotic invasive plants of southern forests

PlantCommon name Scientific name description

Silktree or mimosa tree Albizia julibrissin TreeChinaberry Melia azedarach TreeTallowtree or popcorn tree Sapium sebiferum TreeTree of heaven or stinktree Ailanthus altissima TreeEmpress or princess tree Paulownia tomentosa TreeBicolor lespedeza Lespedeza bicolor ShrubBurning bush Euonymus alatus ShrubJapanese privet Ligustrum japonicum ShrubChinese privet Ligustrum sinense ShrubCommon privet Ligustrum vulgare ShrubMultiflora rose Rosa multflora ShrubAutumn olive Elaeagnus umbellata ShrubAmur or bush honeysuckle Lonicera maackii ShrubJapanese barberry Berberis thunbergii ShrubJapanese honeysuckle Lonicera japonica VineJapanese climbing fern Lygodium japonicum VineEnglish ivy Hedera helix VineKudzu Pueraria montana VineMile-a-minute Polygonum perfoliatum VinePeriwinkle Vinca minor VineOriental bittersweet Celastrus orbiculatus VineChinese wisteria Wisteria sinensis VineWinter creeper Euonmus fortunei VineCogongrass Imperata cylindrica GrassJapanese grass or stiltgrass Microstegium vimineum GrassJohnsongrass Sorghum halepense GrassTall fescue Fescue elatior GrassCommon teasel Dipsacus sylvestris HerbCrown vetch Coronilla varia HerbGarlic mustard Alliaria petiolata HerbJapanese knotweed Polygonum cuspidatum HerbMusk thistle Carduus nutans HerbPurple loosestrife Lythrum salicaria HerbSericea or Chinese lespedeza Lespedeza cuneata HerbSpotted knapweed Centaurea maculosa HerbSweet clover Melilotus alba Herb

Source: Miller 1997, USDA Forest Service 1999, Rural Action Inc. 1999.

and diversity were documented inwooded farmlands accompanyingelm death from Dutch elm diseaseand subsequent felling of dead trees(Osborne 1982, 1983, 1985). Thecombination of Dutch elm diseaseand logging reduced the availabilityof suitable nesting cavities for cavity-nesting waterfowl species (Johnsenand others 1994).

Other exotic plant pathogenscontinue to affect wildlife habitatin southern forests by reducing theabundance of valuable forest treespecies. These include dogwoodanthracnose and butternut canker.Flowering dogwoods are valuable tomany wildlife species for their fruitproduction (Martin and others 1951;U.S. Department of Agriculture, ForestService 1999). Butternuts are consumedby many species of forest wildlife.

Exotic plant invaders and forestwildlife—Some troublesome weedpests (such as Johnsongrass, multiflorarose, and kudzu) were intentionallyintroduced as crops for wildlife en-hancement or for erosion control,but later became pests (Pimentel andothers 1999). The majority of weeds,however, were accidentally introducedwith crop seeds from ship-ballast soil orfrom various imported plant materials,such as ornamental plants. Some exoticinvasive plants, such as Chinese privet,are shade tolerant and once establishedare capable of invading relatively denseforests. Many other invasives, such askudzu, mimosa tree, or princess tree,are less adept at colonizing deeplyshaded, mature forests except alongedges, in natural or artificial forestcanopy openings, or in disturbedor fragmented forests. Exotic plantshave been spread by overgrazing,land use changes, application offertilizers, and the use of agriculturalchemicals (Westbrooks 1998). Otherhuman activities result in disturbedenvironments and encourage invasiveplants. These activities include farming,creation of highway and utility rights-of-way, clearing land for homesand recreation areas, such as golfcourses, and constructing ponds,reservoirs, and lakes.

Millions of acres of forest land inthe Southeast are occupied by exoticinvasive plants. For many species,the acreage infested and spread ratesare unknown. Kudzu and Japanesehoneysuckle occupy more than 7

million acres each, and their spreadrates are increasing (Miller 1997).Clearcuts in the South can becomeinfested with exotic vines, such asJapanese honeysuckle and mile-a-minute, which can prevent thegrowth of seedlings and retard timberyields (Campbell 1997, Nuzzo 1997).English ivy and Japanese honeysucklecan overgrow and eventually killtrees and understory plants and havefundamentally altered the characterand structure of some forests (U.S.Congress, Office of Technology

Assessment 1993). The herbaceous orshrub layers of large but unrecordedareas of forest are being transformedinto virtual monocultures by exoticvines, herbs, and shrubs. In somecases, these plant invasions have beenshown to reduce forage or cover forwildlife (Campbell 1997). Table 3.1lists some exotic plant species thatare particularly noxious in forests inthe Southern United States.

In recent years the impact of invasiveexotics on biodiversity has become amajor concern. Biological invasions


by exotic species may displace nativeanimals and plants, disrupt nutrientand fire cycles, and change the patternsof plant succession (Westbrooks 1998).Invasive exotic plants encroach intoparks, preserves, wildlife refuges,and urban areas. Since many of theseareas are significant for maintainingindigenous animals and plants (U.S.Congress, Office of TechnologyAssessment 1993), the responsibleland management agencies are forcedto expend increasing resources tocontrol the most troublesome invaders.Approximately 61 percent of ournational parks have at least a moderatelevel of exotic plant infestation: severelyimpacted parks include the GreatSmoky Mountains. An estimated 400of 1,500 vascular plant species in theGreat Smoky Mountains National Parkare exotic, and 10 of these are currentlydisplacing and threatening other speciesin the park (Pimentel and others 1999).Invasive exotic species are consideredto be the second most importantthreat to biodiversity, after habitatloss and degradation. Approximately42 percent, or about 400, of the 958species that are listed in the UnitedStates as threatened or endangeredunder the Endangered Species Act areat risk because of competition with orpredation by exotic species (Wilcoveand others 1998). In south Florida,exotic plant species, such as Australianpine, Brazilian pepper, and leatherleaffern, are invading disturbed areasand outcompeting native vegetation,reducing Key deer foods and habitat(U.S. Fish and Wildlife Service 1999).In spite of the severity of exotic plantinvasion in southern forests, theimpacts to forest wildlife in the Southhave only been sparsely documented.More information about the effectsof exotic invasive plants on forestecosystems can be found in chapter 2.

Exotic plant invaders andforest wildlife: use of exotic plantspecies by insect herbivores—

Many exotic invasive plant species lackinsect herbivores adapted to live andfeed on them. This factor likelycontributes to their rapid spread.The number of plant-feeding insectsassociated with various trees is areflection of the cumulative abundanceof that tree throughout geologicalhistory (Southwood 1961). Recentlyintroduced exotic tree species generallysupport relatively few insect species

compared to abundant native treespecies. The Chinese tallow tree is aninvasive exotic that has spread rapidlyacross the Southern United States.Insects likely control the spread of thistree in its native China, and the lackof insect predation has aided its spreadin the United States. Only one species,the leaf-footed bug, has been reportedcausing fruit damage to this exotictree (Johnson and Allain 1998).

Exotic plant invaders andforest wildlife: use of exoticplant species by forest wildlife—

Despite the tendency of some exoticplant invaders to form dense mono-cultures that exclude native floraand fauna, many species of southernwildlife use exotic plant species forforage and cover. Indeed, some invasiveplant species in southern forests wereintroduced because they were con-sidered beneficial for wildlife habitat(Miller 1997). For instance, multiflorarose was promoted in the 1930s bythe U.S. Soil Conservation Service forerosion control and as living fences forlivestock (Plant Conservation Alliance –Alien Plant Working Group 2002).Soon after, however, state conservationagencies promoted its value as wildlifecover for pheasants, bobwhite quailand cottontail rabbits, and as food forsongbirds. These agencies encouragedits use by distributing free rootedcuttings to landowners. Other exoticplants that were at one time promotedby government agencies or privategroups for wildlife cover or foodsources include Japanese honeysuckle,exotic bush honeysuckles (includingAmur honeysuckle), Chinese lespedeza,bicolor lespedeza, and Chinese privet(Miller 1997, Plant ConservationAlliance – Alien Plant Working Group2002, Virginia Natural HeritageProgram 2002).

The value of Japanese honeysuckleboth as cover and a food source forsongbirds, gamebirds, hummingbirds,small mammals, and deer has beendocumented (Hugo 1989, Martinand others 1951, Miller 1997). Otherexotic honeysuckles, such as Amurhoneysuckle, also have been docu-mented as food and cover for birdsand small mammals (Martin andothers 1951, Whelan and Dilger1992, Williams and others 1992).

Multiflora rose is an invasive exoticshrub that was widely promoted byconservation agencies in the 1930s for

cover, wildlife food, and as living fences(Miller 1997). It provides excellenthabitat for gamebirds and songbirds(Martin and others 1951, Morgan andGates 1982) and for cottontail rabbits(Morgan and Gates 1983).

Japanese and Chinese privets areinvasive exotic shrubs that can replacenative understory species and preventforest regeneration in riparian forestsand bottomland hardwood-pine forests(Miller 1997). Privets are used for foodand habitat by birds, and their seedsare widely dispersed by birds (Martinand others 1951, Miller 1997). Chineseprivet also has been documented innorthwestern Georgia as an importantcomponent of fall and winter dietsof the white-tailed deer (Stromayerand others 1998).

Exotic shrubs in the buckthorn familyprovide excellent nesting and feedinghabitat for many species of songbirds(Whelan and Dilgar 1992). The exoticshrub bicolor lespedeza provides foodfor songbirds, gamebirds, and hoovedbrowsers, including white-tailed deer(Martin and others 1951, Miller 1997).

The Chinese tallow tree in coastalSouth Carolina is used heavily bymore than 14 bird species (Renneand others 2000). The Russian oliveprovides feeding habitat for songbirds,gamebirds, and hooved browsers(Martin and others 1951). Chinaberryis eaten to a limited extent by song-birds (Martin and others 1951).

Although these exotic invasiveplant species provide habitat andfood for southern wildlife species,no scientific investigations were foundthat compared the relative habitat valueof these exotic invaders to the nativeflora that they displaced. In addition,no scientific investigations were foundthat documented the effects of exoticplant species invasions on a broadspectrum of southern forest wildlifespecies, including sensitive habitatspecialists. The past introduction ofexotic plants for wildlife managementhas unintentionally led to severeinvasive exotic species problems.Many of the intended habitat benefitsof these invasive species can be foundin carefully selected native species.See the National Park Service Web siteat http://nps.gov/plants/alien/fact.htmfor some suggested native plantalternatives. Introduction of exoticplant species for wildlife enhancement


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should be approached with caution toavoid future invasive species problems.

Effects of exotic animals on forestwildlife: exotic insect pests andforest wildlife—More than 2,000arthropod species and 11 earthwormspecies have been introduced into theContinental United States, includingapproximately 500 exotic insect andmite species (Pimentel and others1999). About 360 exotic insect specieshave become established in Americanforests and approximately 30 percentof these species have become seriouspests. Although the negative effectsof invertebrate pest species, such asthe gypsy moth and the balsam woollyadelgid, to southern forests have beenwell documented (see chapter 17),much less information is availableabout their effects on wildlife. Seechapter 17 for a description of theeffects of insects and other forestpests on southern forests.

Balsam woolly adelgid—The balsamwoolly adelgid is an aphid that inflictssevere damage in balsam-fir forests(Pimentel and others 1999). Thebalsam woolly adelgid has killed upto 95 percent of the Fraser firs inthe Southern Appalachians.

Resultant habitat losses have impactedforest wildlife. A few species, suchas the larvae of the moth Semiothisafraserata, may depend exclusivelyon the Fraser fir for food (Stein andFlack 1996). Other species, such asthe Weller’s salamander, are endemicto the spruce-Fraser fir habitat of theSouthern Appalachians. Changes inthe avifaunal composition of Fraserfir forests were documented in theSouthern Appalachians followingdestruction of the Fraser fir canopyby the balsam woolly adelgid (Alsopand Laughlin 1991, Rabenold andothers 1998).

Frazier fir bark provides substratefor eight rare species of mosses andliverworts (Stein and Flack 1996).The endangered spruce-fir mossspider lives in moss mats that areonly found in the spruce-Fraserfir forests of Southern Appalachia(U.S. Fish and Wildlife Service 1998).Loss of the tree canopy (due to thebalsam woolly adelgid) has resultedin increased light and temperatureand decreased moisture on the forestfloor, causing the moss mats on whichthe spider depends to dry up andbecome unsuitable.

The endangered Virginia northernflying squirrel and the endangeredCarolina northern flying squirrel arefound in conifer-hardwood ecotonesor forest mosaics of spruce-fir assoc-iated with various hardwoods in highelevations of the Southern Appalachians(U.S. Fish and Wildlife Service 1990a).Although decimated by past loggingof spruce forests, these two subspeciesare currently threatened by severalfactors including habitat damage toconifer-hardwood ecotones by thebalsam woolly adelgid and gypsy moth.

Gypsy moth—The gypsy mothwas accidentally released in Medford,MA, in 1869. The spread rate ofgypsy moths from 1966 through1990 was approximately 13 milesper year (Liebhold and others 1995).Gypsy moths feed on numeroustrees, shrubs, and vines but preferoaks (U.S. Department of Agriculture,Forest Service 1999).

Infestation by gypsy moths canimpact forest wildlife habitat in severalways. Severe infestations can reducethe production of acorns and mastproduced by susceptible tree species,reducing mast available for wildlife.However, resultant dead trees can serveas dens for some wildlife (Brooks andHall 2000). Defoliation of the over-story can displace closed-canopy birdspecies, while increasing the abundanceof open-canopy species (MichiganState University 1997). In some heavilyoverstocked forests lacking naturaldisturbances (such as fire), defoliationcan benefit forest birds dependent uponsmaller openings in mature hardwoodor mixed forests. Beneficiaries includesome declining or priority species, suchas Canada warblers and white-throatedsparrows (Hunter and others 2001b).

Following gypsy moth infestations,sensitive shade-dependent understoryplants can become stressed by theincreased sunlight reaching the forestfloor (U.S. Department of Agriculture,Forest Service 1999). Defoliation ofthe overstory increases the growth ofshrubs, grasses, and herbs providingsome wildlife with additional coverand forage (Brooks and Hall 2000).

Red imported fire ants—The redimported fire ant infests more than250 million acres in the United States(Allen and others 1994). Fire ants couldspread across almost a quarter of theNation before range limits are reached.Southern States already infested by the

species suffer damages totaling morethan $1 billion per year (Pimenteland others 1999).

Red imported fire ants are mostabundant in open habitats with dis-turbed soil, where sunlight can reachthe soil surface (Stiles and Jones 1998).They are rare in shaded or undisturbedhabitats, such as intact forests. Fire antscan invade southern forests along themargins of linear disturbances, suchas roads or power lines. In areas wherethe red imported fire ant is abundant,native ants are displaced by compe-tition. Although omnivorous, thespecies feeds voraciously on livingand dead insects. Native arthropoddiversity and abundance often arereduced in heavily infested areas(Allen and others 1994, Stiles andJones 1998, Tedders and others 1990).

Red imported fire ants havehad detrimental impacts on manywildlife species (Allen and others1994). Reptiles and amphibians tendto be vulnerable to displacement byfire ants when they compete for sharedprey (invertebrates) or have an eggstage vulnerable to predation duringtimes of high fire ant activity. Fire antshave been documented to destroy nestsand cause hatchling mortality of thethreatened gopher tortoise (Allen andothers 1994, U.S. Fish and WildlifeService 1990b).

Fire ants compete with nativescavengers that feed on dead animalsand fallen fruit. They have beenimplicated in declines of ground-nesting birds, such as quail and turkey,because they attack newly hatchedyoung (U.S. Department of Agriculture,Forest Service 1999). Nest and chickpredation by the red imported fire anthas been documented for many birdspecies (Allen and others 1994). Thered imported fire ant has been linkedto declines of migratory winteringpopulations of the loggerhead shrike(Grisham 1994). Injuries or deathto white-tailed deer fawns and othernewborn small mammals due toattack by the red imported fire anthave been widely reported (Allenand others 1994).

Effects of exotic animals on forestwildlife: effects of exotic wildlifeon native forest wildlife—Stein andFlack (1996) estimate that at least2,300 species of exotic animals nowinhabit the United States. This totalincludes an estimated 20 species of


Table 3.2—Introduced terrestrial wildlife species in southern forests

AnimalCommon name Scientific name description

Cuban treefrog Osteopilus septentrionalis AmphibianGreenhouse frog Eleutherodactylus planirostris AmphibianBrown anole Anolis sagrei ReptileRing-necked (green) pheasant Phasianus colchicus BirdPlain chacalaca Ortalis vetula BirdRock dove Columba livia BirdRose-ringed parakeet Psittacula krameri BirdBudgerigar Melopsittacus undulatus BirdCanary-winged parakeet Brotogeris versicolurus BirdMonk parakeet Myiopsitta monachus BirdEuropean starling Sternus vulgaris BirdSpot-breasted oriole Icterus pectoralis BirdHouse sparrow Passer domesticus BirdRhesus macaque Macaca mulatta MammalBlack rat Rattus rattus MammalNorway rat Rattus norvegicus MammalHouse mouse Mus musculus MammalWild boar Sus scrofa MammalFallow deer Cervus dama MammalSambar deer Cervus unicolor Mammal

Source: Echternacht and Harris 1993, Choate and others 1994.

exotic mammals, 97 species of exoticbirds, and 53 species of exotic reptilesand amphibians. These species costthe U.S. economy about $27.5 billionevery year (Pimentel and others 1999,Scientific American 1999). Many of thelarger exotic animals were deliberatelyimported for aesthetic, sport hunting,or livestock purposes. Deliberateimports include European starlings,European wild boars, ring-neckedpheasants, and feral pigs. Other smallerexotic pests, such as rats, mice, redimported fire ants, and balsam woollyadelgid, arrived hidden in cargo holds,shipping containers, produce, andimported forest products. Echternachtand Harris (1993) indicated that atleast 50 exotic wildlife species havebecome established in the SoutheasternUnited States comprising about 8percent of the 625 native and exoticwildlife species. Table 3.2 is basedon their wildlife and faunal description.It contains a list of exotic wildlifespecies that inhabit southern forests.

Feral pigs—Feral pigs that descendedfrom domestic farm animals andEuropean wild boars that wereintroduced for sport hunting nownumber about 4 million across the

United States. Together, they cost theeconomy more than $800 million indamages per year (Pimentel and others1999). Florida has about 0.5 millionand Texas has 1 to 1.5 million.

The effects of wild pigs vary greatlyfrom place to place, depending onthe density of pigs and the sensitivityof the ecosystems involved (Singer1981). Their rooting habit hasdamaged sensitive forest habitatsacross the South, including rarewetlands and springs in the Ozark-Ouachita Highlands (U.S. Departmentof Agriculture, Forest Service 1999).Wild pigs compete with wild turkeysand white-tailed deer for acornsand other foods. They tear up rottenlogs that provide habitat for manyamphibians and reptiles. In addition,hogs destroy the nests of turkeys, ruffedgrouse, and other ground-nesting birds(Miller and Leopold 1992, Sealanderand Heidt 1990). Wild pigs also carrydiseases, such as brucellosis andpseudorabies that represent a risk tonative wildlife (New and others 1994,Peine and Lancia 1990, Tozzini 1982).No antibodies for serious diseaseswere detected in a 1990 survey of wildpigs in the Great Smoky Mountain

National Park, however (New andothers 1994).

Wild pigs occur in 13 nationalparks but are especially problematicin the Great Smoky MountainsNational Park (Singer 1981). Wildboars invade high-elevation northernhardwood communities from aboutApril through August where theirrooting has reduced understory plantcover up to 87 percent. Up to 77percent of all logs and branches aremoved in heavily rooted areas. Red-backed voles and shrews are normallycommon in pristine stands, but areabsent in rooted areas.

Feral cats—Domestic cats, includingboth pets and free-ranging animals,now number about 100 million inthe United States (Coleman and others1997). The occurrence of cats tends tobe concentrated around areas of humanhabitation. Studies of free-rangingdomestic cats indicate that smallmammals comprise about 70 percentof their prey, and birds constitute about20 percent. Nationwide, free-rangingrural cats probably kill more than abillion small mammals and hundredsof millions of birds each year. Free-ranging cats are a serious threat toground-nesting birds, such as turkeyand quail (Miller and Leopold 1992;U.S. Department of Agriculture,Forest Service 1999), and also attackshrub-nesting songbirds. In Florida,free-ranging cats are contributing tothe imperiled status of several federallylisted species, including the LowerKeys marsh rabbit, several types ofbeach mice, and woodrats.

Free-ranging cats can outnumberand compete with native predators,including hawks and weasels (Colemanand others 1997). Cat predation maydeplete winter populations of microtinerodents and other prey of red-tailedhawks, marsh hawks, and Americankestrels (George 1974). Free-rangingcats also can potentially transmit newdiseases to forest wildlife, includingfeline leukemia to cougars (Jessupand others 1993) and feline distemperand feline immunodeficiency virusto the endangered Florida panther(Roelke and others 1993).

Feral dogs—Free-ranging and feraldomestic dogs are nearly ubiquitousacross the United States (Drost andFellers 2000); many problems arereported in Florida and Texas (Pimenteland others 1999). Free-roaming dogs


TERRESTRIAL

Table 3.3—Some southeastern forest bird species and their sensitivitiesto urban and suburban development

Urban/suburbanCommon name Scientific name association

Mature-forest assemblage (late successional forests)Pine warbler Dendroica pinus TolerantRed-eyed vireo Vireo olivaceus IntolerantRed-bellied woodpecker Melanerpes carolinus TolerantWood thrush Hylocichla mustelina IntolerantOvenbird Seiurus aurocapollus IntolerantHooded warbler Wilsonia citrina IntolerantAcadian flycatcher Empidonax virescens IntolerantScarlet tanager Piranga olivacea IntolerantNorthern parula Parula americana IntolerantBlack-and-white warbler Mniotilta varia IntolerantHairy woodpecker Picoides villosus TolerantPileated woodpecker Dryocopus pileatus IntolerantYellow-throated warbler Dendroica dominica IntolerantProthonotary warbler Protonotaria citrea IntolerantKentucky warbler Oporornis formosus IntolerantLouisiana waterthrush Seiurus motacilla IntolerantShrubland assemblage (early successional clearcuts)Indigo bunting Passerina cyanea IntolerantYellow-breasted chat Icteria virens IntolerantCommon yellow-throat Geothlypis trichas IntolerantWhite-eyed vireo Vireo griseus IntolerantPrairie warbler Dendroica discolor IntolerantField sparrow Spizella pusilla IntolerantGray catbird Dumetella carolinensis TolerantForest-edge assemblage (fragmented landscapes)Brown-headed cowbird Molothrus ater TolerantNorthern mockingbird Mimus polyglottos TolerantChipping sparrow Spizella passerina TolerantAmerican robin Turdus migratorius TolerantEastern bluebird Sialia sialis TolerantCommon grackle Quiscalus quiscula TolerantEastern kingbird Tyrannus tyrannus Rural/agriculturalRed-headed woodpecker Melanerpes erythrocephalus Somewhat tolerantOrchard oriole Icterus spurius Rural/agriculturalHouse finch Carpodacus mexicanus Tolerant

continued

chase and harass indigenous wildlife(Sealander and Heidt 1990; U.SCongress, Office of TechnologyAssessment 1993) and disturb ground-nesting birds, such as quail and wildturkeys, by attacking adult birds andconsuming eggs and hatchlings (Millerand Leopold 1992; U.S. Departmentof Agriculture, Forest Service 1999).In southeast Alabama, free-rangingdogs prey upon the threatened gophertortoise and destroy gopher tortoiseburrows (Causey and Cude 1978,U.S. Fish and Wildlife Service 1990b).In south Florida, dog-related deathsare the second most frequent causeof human-induced mortality for theendangered Key deer (U.S. Fishand Wildlife Service 1999).

Free-ranging dogs have the abilityto interbreed with coyotes and thefederally endangered red wolf(Sealander and Heidt 1990; U.S.Department of Agriculture, ForestService 1999).

European starlings—After theintroduction of European starlingsin the late 1800s, population growthand range expansion were explosive.Starling populations now appear tohave leveled off or are decreasing inmost areas across the country (Robbins2001). Although starlings consumenoxious insects and weed seeds, theyalso compete with native species forfood and nesting cavities. Displacementof native birds by starlings has beendocumented in areas of the countrywith limited nest sites (Weitzel 1988).Starlings are known to be a veryaggressive species when competingfor or usurping cavities from otherbirds (James and Neal 1986).

Effects on reproduction andfecundity of red-bellied woodpeckerswere documented due to nest cavitycompetition with starlings (Ingold1994, 1996; Ingold and Densmore1992). The effects of starling nest cavitycompetition on northern flickers andred-headed woodpeckers were foundto be less severe. Competitive cavitylosses for red-headed and northernflickers have more serious implications,however, since these two species arecurrently declining. Starlings arecommon in urban and agriculturalwoods, but are seldom found indensely forested areas (Ingold andDensmore 1992). Red-bellied wood-peckers that nest in more heavilywooded environments are more

successful in avoiding competitionwith starlings. Starlings also competewith other native birds, including theeastern bluebird and purple martin, forcavity nest sites (U.S. Department ofAgriculture, Forest Service 1999).

House sparrows—Following a seriesof introductions in the United States,house sparrows became well establishedacross the continent by 1910. Currently,populations appear to be stable ordecreasing in most areas of the country(Robbins 2001). House sparrows arefound mainly in urban and agricultural

areas (James and Neal 1986) andare seldom found in predominantlyforested areas.

Although they commonly nest inman-made structures, house sparrowsalso use deteriorating nests of otherspecies, woodpecker cavities, andnesting boxes intended for otherspecies. House sparrows have beendocumented to usurp cavities from red-bellied and red-headed woodpeckers(Ingold and Densmore 1992). Inaddition to native woodpeckers, housesparrows have been known to harass


Table 3.3—Some southeastern forest bird species and their sensitivitiesto urban and suburban development (continued)

Urban/suburbanCommon name Scientific name association

Habitat generalist assemblageCardinal Cardinalis cardinalis TolerantCarolina wren Thryothorus ludovicianus TolerantTufted titmouse Baeolophus bicolor TolerantBlue-gray gnatcatcher Polioptila caerulea IntolerantCarolina chickadee Poecile carolinensis TolerantBlue jay Cyanocitta cristata TolerantGreat crested flycatcher Myiarchus crinitus Somewhat tolerantSummer tanager Piranga rubra IntolerantDowny woodpecker Picoides pubescens TolerantYellow-billed cuckoo Coccyzus americanus IntolerantEastern wood pewee Contopus virens IntolerantMourning dove Zenaida macroura TolerantCommon crow Corvus brachyrhynchos TolerantNorthern bobwhite Colinus virginianus IntolerantBrown thrasher Toxostoma rufum IntolerantNorthern flicker Colaptes auratus TolerantAmerican goldfinch Carduelis tristis TolerantRed-shouldered hawk Buteo lineatus TolerantYellow-throated vireo Vireo flavifrons IntolerantRuby-throated hummingbird Archilochus colubris TolerantEastern phoebe Sayornis phoebe TolerantEastern screech-owl Otus asio TolerantCommon nighthawk Chordeiles minor TolerantWhite-breasted nuthatch Sitta carolinensis Tolerant

Source: Canterbury and others 2000 [based on results from: Engels and Sexton (1994), Smith andSchaefer (1992), Dowd (1992), Beissinger and Osborne (1982), Rottenborn (1999), Linehan andothers (1967), Blair (1996), Goldstein and others (1986), Friesen and others (1995), Long andLong (1992), Askins and Philbrick (1987), Aldrich and Coffin (1980), Bolen and Robinson (1995),Zimmerman (1991), and Hines and Anastasi (1973)].

other native birds including robins,yellow-billed cuckoos, and black-billed cuckoos. They can displacenative eastern bluebirds, wrens,purple martins, and cliff swallowsfrom their nesting sites (Arcieri 1992,Pimentel and others 1999). The deathsof adult and nestling bluebirds weredocumented in South Carolina resultingfrom aggressive competition withhouse sparrows (Gowaty 1984).

Effects of Urbanizationon Forest Wildlife

Effects of urbanization on forestbird communities—A number ofstudies investigated changes to birdcommunities by comparing anurbanized site versus a less urbanized(or more forested) site. Many investi-gators found that urbanizationdecreased the species diversity of the

avian community and increased aviandensity (or bird biomass), favoringdominance by a few species. Birdspecies vary in sensitivity to urban-ization, leading to loss of sensitivespecies and a shift in the speciescomposition of urban versus forestbird communities. Habitat specialists,including many forest insectivores,neotropical migrants, and forest interiorspecies, have been documented tobe less tolerant of urbanization.Beissinger and Osborne (1982), Smithand Schaefer (1992), Franklin andWilkinson (1996), Kluza and others(2000), Croonquist and Brooks (1993),and Dowd (1992) all documented shiftsin avian species composition withincreasing urbanization.

Some investigators studied theresponse of bird communities acrossseveral sites or along a gradient of

increasing urbanization. Gradientstudies revealed a less clear patternin bird species diversity and densitypeaks; in some cases the pattern shiftedseasonally. However, shifts in the avianspecies composition were generallyfound as urbanization increased(Blair 1996, Clergeau and others1998, Lancaster and Rees 1979,Rottenborn 1999).

Others investigated changes in thebird community at a single site throughtime as the area became urbanizedor more forested. Butcher and others(1981), Askins and Philbrick (1987),Aldrich and Coffin (1980), Longand Long (1992), and Horn (1985)documented the loss of sensitiveforest bird species after urbanizationor their return after reforestation.

Table 3.3 lists selected forest birdspecies in the Southeastern UnitedStates and their tolerances to urbanand suburban development.

Urban fragmentation andedge effects—Forest size and levelof fragmentation and the effects onbreeding birds—Increasing urban-ization fragments forest habitat intosmaller and more isolated tracts.Research on breeding forest birdshas shown that some species haveminimum area requirements. Manystudies documented declines in thenumbers of forest breeding migratorybirds in small isolated forest patches(Danielson and others 1997). Fragmen-tation is considered to be a primarycontributing factor to observedneotropical migrant declines.

Whitcomb and others (1981) foundthat many neotropical migrant speciesbecame increasingly rare as the size ofthe forest decreased. In addition, areasensitivities varied depending on thedegree of isolation from larger foresttracts. They concluded that forest tractsneeded to contain hundreds or perhapsthousands of acres to conserve popu-lations of some forest bird species.Robbins and others (1989) suggestedthat when managing forests for wildlife,top priority should go toward providingfor the needs of area-sensitive or rarebird species. When conservation oflarge contiguous forest tracts is notpossible, they suggested that severalmoderately sized contiguous forestscould be helpful in maintainingrare forest breeding birds.


TERRESTRIAL

Reduced reproductive successof forest nesting birds in small orfragmented forests may be due toincreased nest predation or nestparasitism by brown-headed cowbirds.Nest parasitism is associated withbrown-headed cowbirds, which laytheir eggs in the nests of other species.These hosts then raise cowbirds atthe expense of their own offspring.Nest predation can be caused by acombination of many avian, mam-malian, and reptile species. Rates ofnest predation have been found tobe higher in small forest tracts thanin large forest tracts, and small urbanforest tracts experience higher rates ofpredation than comparably sized foresttracts in isolated rural areas (Wilcove1985). Migratory songbird populationssuffer the most serious effects fromincreased predation in small foresttracts. Keyser and others (1998),Donovan and others (1995), Robinson(1992), and Robinson and others(1995) all documented reducedreproductive success of neotropicalmigrants and other forest nesting birdspecies in fragmented forests due tohigher rates of nest predation and/ornest parasitism.

Recently, investigators stress theimportance of overall forest coveror landscape levels of fragmentationsurrounding a local area when eval-uating the presence or nesting successof area-sensitive or forest-interiorbirds. As indicated by Villard (1998),preference for forest-interior habitator avoidance of small fragments tendsto focus attention on the local scale,whereas processes underlying thesephenomena may take place overlandscape or even continental scales.Therefore, forest-interior preferenceand area sensitivity should be consid-ered in a landscape context. In onestudy, forest cover in approximately40-square-mile study plots was foundto be the most important factor affect-ing the distribution of forest birds(Trzcinski and others 1999). Compar-atively, the independent measures offorest fragmentation produced effectsthat were inconsistent and far lessimportant than overall forest cover.In addition, the reduction in nestingsuccess of forest birds due to nestpredation and parasitism was muchgreater in heavily fragmented land-scapes with low forest cover thanin heavily forested landscapes (Hartleyand Hunter 1998, Robinson and others

1995). Similarly, no differences weredetected in the breeding success ofworm-eating warblers in small andlarge forest tracts when high amountsof forest canopy cover were presentin the surrounding landscape (Galeand others 1997).

In addition, landscape-level factorsmay partially affect the distributionof mammalian nest predators and,potentially, songbird nest-predationrates. A combination of local features,such as proximity to some types ofedge, as well as broader landscape-level features, such as land use patterns,was determined to influence the abun-dance of these mammals (Dijak andThompson 2000). At a broader scale,raccoons were more abundant inagricultural landscapes with highdensities of streams than in forestedlandscapes with low densities ofstreams. Opossums were more abun-dant in heterogeneous landscapes withwidely spaced patches of forest andhigh densities of riparian habitat.

A review of Breeding Bird Surveytrends for the southern Piedmontphysiographic area might lead one toconclude that perhaps urbanization isnot a serious threat to sensitive forestbreeding birds. As indicated in Hunterand others (2001a), very few vulnerablespecies in the southern Piedmont havedeclined overall from 1966 to 1996.This apparent stability, however, mayreflect an overall increase in forestacreage and maturation of the forestsduring this period. As further sum-marized in Hunter and others (2001a),wood thrushes and red-eyed vireoshave shown consistent declines withinpatches of mature forest in Piedmontsuburban areas, such as Atlanta, GA.In addition, a number of area-sensitivewoodland bird species, such asnorthern parulas, black-throated greenwarblers, Swainson’s warblers, andworm-eating warblers, have populationcenters in relatively more forested areas,such as the southern Blue Ridge andthe South Atlantic Coastal Plain, butare nearly absent as a breeding speciesover much of the southern Piedmont(Hunter and others 2001a). Perhapsmore revealing than population trenddata alone for woodland warblers andother sensitive mature forest species isthe absolute abundances for thosespecies as derived from the BreedingBird Survey data (Hunter, W.C.,May 2002. Unpublished analysis on

Breeding Bird Survey data. 4 p. On filewith: Kenneth L. Graham, U.S. Fishand Wildlife Service, EcologicalServices, Suite 200, 1875 CenturyBlvd., Atlanta, GA 30345). Absoluteabundances of these species in heavilyfragmented physiographic areas, suchas the southern Piedmont and thesouthern ridge and valley/southernCumberland Plateau, are clearly muchlower than those exhibited by moreheavily forested, less fragmentedphysiographic areas, such as thesouthern Blue Ridge and northernCumberland Plateau.

In the face of very low absolute abun-dances of sensitive woodland birdspecies, positive or negative populationtrends within heavily urbanizing areas,such as the southern Piedmont, mayreflect habitat conditions and popula-tion trends in nearby physiographicareas that actually support thosespecies’ population centers and actas source populations. Ironically, someof the most forested physiographicareas in the Southeast have exhibitedthe steepest declines in forest birdsin recent years. These areas have longbeen considered to be populationsources for forest nesting birds (andstill are, but to a more limited extentthan previously thought) (Simons andothers 2000). See chapter 4 for moreinformation concerning populationdeclines of forest birds in more forestedphysiographic regions and for trends inwood-warbler species in the Piedmont.

Connective corridors and offsettingthe deleterious effects offragmentation—The presence ofconnective corridors may help toreduce the isolation of wildlifepopulations in fragmented forests(MacClintock and others 1977,Machtans and others 1996, Wegnerand Merriam 1979). Corridors mayprovide a connection that allowswildlife to move from one patch toanother across an intervening, inhos-pitable landscape. This phenomenonhas been especially well documentedfor disturbance-dependent grasslandand scrub-shrub bird species, such asBachman’s sparrow, in largely forestedareas (Dunning and others 1995). Itis not obvious that animals possessingthe mobility of birds need corridorsto cross-fragmented landscapes, butit appears that the open space betweenforest islands is a barrier to movementof some songbirds (Whitcomb and


others 1981). Gaps of 250 feet ormore produced isolation characteristicsfor some songbirds in small forestfragments created by power lines androads (Robbins and others 1989). Suchgaps may not represent as serious aproblem in largely forested landscapes,however (Gale and others 1997). Someinvestigators question the conservationvalue of corridors or question whethersufficient experimental evidenceexists to draw conclusions on theirbenefits (Inglis and Underwood 1992,Simberloff and others 1992). Severalpotential negative effects and dis-advantages of corridors should beconsidered prior to their use in over-coming fragmentation (Simberloff andothers 1992). Disagreement over thevalue of corridors to overcome theeffects of fragmentation for variousspecies is likely to continue for sometime. The use of corridors and the effectof fragmentation on movement patternsseem to be highly species-specific(Debinski and Holt 2000).

Fragmented forests have a greaterproportion of edge habitats. Edges havegenerally been regarded by wildlifemanagers to have a positive effect onwildlife because the number of speciesincreases near habitat edges (Yahner1988). This positive effect likelyremains true for birds in predominantlyforested landscapes. In fragmentedlandscapes, however, maximizingspecies diversity is not always adesirable objective in light of thenumber of rare species that depend onlarge areas of habitat. Rates of nestpredation and brood parasitism aregreater at edges for some forest nestingbirds (Gates and Gysel 1978), especiallyas overall forest cover becomesincreasingly fragmented (Donovan andothers 1997). Paton (1994) reviewed anumber of studies that dealt with birdnesting success as a function of distancefrom an edge. Most studies found thatnesting success decreased near edges asa result of increasing nest predationand parasitism rates. The strongesteffects appeared to occur within about125 feet of the edge. Indigo buntingnests along abrupt forest edges, suchas agricultural edges, wildlife openingsor campgrounds, had nearly twicethe nest predation rate as those foundalong more gradual edges, such asthose created by treefalls, streamsides,and gaps created by selective logging(Suarez and others 1997).

While the results of many investi-gations indicate that nesting success forforest birds is reduced by the proximityof edges, recent information indicatesthat such effects depend on the natureof the surrounding landscape. Hartleyand Hunter (1998) reviewed variousnest predation studies and concludedthat nest predation rates decreasedas the amount of overall forest coverincreased. Edge effects were moreapparent in largely deforested land-scapes. Donovan and others (1997)found that nest predation rates weresignificantly higher near edges, butthese increased rates were apparentonly in highly and moderatelyfragmented landscapes and not inunfragmented landscapes. The ovenbirdmay be an exception, however. Evenin an extensively forested landscape,slightly reduced rates of breedingsuccess were documented for ovenbirdsnear forest edges (King and others1996). Still, ovenbird reproductivesuccess remains high overall, andother sensitive neotropical migrantsfare better in highly forested landscapes(Gale and others 1997). Ovenbirdsreproduce well in midsuccessionalforests, and since such conditions areplentiful throughout eastern forests,the ovenbird is not considered aconservation priority species. Seechapter 1 for more information aboutthe effects of forest fragmentation onforest wildlife.

Not all investigators agree that highernest predation rates occur in smallerforests or along forest edges (Friesenand others 1999, Haskell 1995, Matessiand Bogliani 1999, Yahner 1996,Yahner and Mahan 1996). Studies inlarge contiguous forest areas, such asthe Great Smoky Mountains NationalPark, indicate that although these areasenjoy an overall higher nesting successrate for forest nesting birds (such aswood thrush), they may also supporta more diverse and abundant predatorcommunity than more disturbed or lesscontiguous sites (Simons and others2000). In addition, the magnitude andpatterns of nest parasitism by brown-headed cowbirds is not consistentamong studies (Coker and Capen 1995,Donovan and others 1997, Evans andGates 1997, Gates and Gysel 1978,Hahn and Hatfield 1995, Robinson1992, Robinson and others 1995).

Effects of urban environments onbird abundance and nesting

success—In urban areas, forest-breeding birds may have lowerabundances and lower nesting success.A 10-acre woodlot without any nearbyhouses had greater species richness andhigher abundances of neotropicalmigrant species than did a 60-acreurbanized woodlot, indicating that thediversity and abundance of neotropicalmigrant birds decreased with increasedurban development (Friesen and others1995). Golden-cheeked warblersdeclined near urban development,apparently due to the increasedpresence of blue jays and greater nestpredation (Engles and Sexton 1994).Declines of neotropical migrants weredocumented over a 50-year periodin the North Carolina HighlandsPlateau, likely due, in part, to the closeproximity of residential developmentand urban fragmentation (Holt 2000).Nest predation rates were found tobe greater for woodlands in the vicinityof human settlement (Matessi andBogliani 1999). Mammalian nestpredators were found to be moreabundant in floodplain forests thatadjoined residential and agriculturallands (Cubbedge and Nilon 1993).

Urban areas as habitat for birds—Urban woodlands are unsuitablehabitat for many forest bird species,including many neotropical migrantbirds, birds that require large habitatareas for breeding, birds that breedonly in forest interior habitats, manyscrub-shrub and grassland species, andthose sensitive to urban disturbance.Urban and suburban preserves tend tobe small and isolated from otherforests. However, urban woodlands stillprovide habitat for some wildlifespecies and seasonally supportmigrating birds. Not all urban habitatsare the same.

Woody vegetation volume isimportant in determining breeding birddiversity in urban settings (Goldsteinand others 1986). Urban woodlotsof 20 acres or more can support denseand diverse populations of breedingbirds, provided that they have adequateshrub understory, mature and deadstanding trees, and vegetative edgetypes of sufficient width and properquality (Linehan and others 1967).Large urban parks with well-preservednatural forest habitat support birdpopulations more characteristic ofnative forests (Gavareski 1976). Urbanparks, cemeteries, schoolyards, and


TERRESTRIAL

other open spaces are prime sitesfor wildlife management (Bolenand Robinson 1995). For example,Washington, DC, has only housesparrows, pigeons (rock doves),and starlings in the downtown area,but nearby in the spring gardenssurrounding the White House,19 species are present.

In urban environments, the objectiveof wildlife management should beto maintain biological diversity byretaining sufficient habitat for themaximum number of wildlife species(Milligan and others 1995). Urbanwildlife habitat designs must considerthe size, composition, connectivity,dynamics of the habitat patches,and human perceptions of the habitatareas. At the same time, however,urban wildlife habitats must be at ascale compatible with the surroundingurban uses. Constraints are necessaryto promote human health and safety,and to meet habitat requirementsof the different wildlife species.

Urban habitats pose additional risksto resident avifauna. An estimated 98million birds are killed each year in theUnited States from window collisionswith high-rise buildings (Bolen andRobinson 1995). In addition, anestimated 2 to 4 million birds arekilled each year in the Eastern UnitedStates due to collisions with commu-nication towers (Weisensel 2000).The relative contributions of thesemortality sources to the declines ofany conservation priority bird specieswere not described in these references.

Effects of urbanization on birdsof prey and scavengers—Birds of prey,such as hawks, eagles, and owls, can bevulnerable to the effects of urbanizationbecause they are at the tops of foodchains, and their home ranges are largerthan those of most other birds (Adams1994). Hawk species differ in theirrequirements for nesting habitat andtolerance for forest openings andhuman disturbance. Cooper’s hawksabandon nest sites when housingconstruction and residentialdisturbance encroach on establishednest sites (Bosakowski and others1993). There is evidence, however, ofadaptability of various hawk species tourban settings. Broad-winged hawks aremore tolerant of forest openings whenselecting nest sites than red-shouldered,red-tailed, or Cooper’s hawks (Titus andMosher 1981). Red-shouldered hawks

in New York and New Jersey havehigher nest productivity with increas-ing distance from human habitation(Speiser and Bosakowski 1995).

Bald eagles generally select wellforested areas near water bodiesand avoid areas of human developmentand areas of high boat and pedestriantraffic (Buehler and others 1991a,1991b; Chandler and others 1995).On the lower Melton Hill Reservoirand the adjoining Clinch River ineastern Tennessee, residential andindustrial development was foundto be the primary factor limitinghabitat suitability for eagle nesting(Buehler 1995).

When not searching for food, blackand turkey vultures tend to preferforested habitats free of buildingsfor roosting and nest sites (Colemanand Fraser 1989). Nests are frequentlylocated away from human disturbancein rock crevices and in roadless,forested, and undeveloped areas.Nesting success for vultures was foundto increase farther from buildings dueto lower disturbance and lessdepredation by dogs.

Although some raptors are sensitiveto urban disturbance, there may bedifferences among individuals, species,and regions of the country. Raptorsthat are tolerant of urban environmentsinclude Mississippi kites, sharp-shinnedhawks, Cooper’s hawks, red-shoulderedhawks, and red-tailed hawks (Adams1994). Urban woodlands, even thosecomposed primarily of exotic vege-tation, lawns, and urban development,are acceptable to some red-shoulderedhawks (Bloom and others 1993).One pair of red-shouldered hawkssuccessfully fledged young within65 feet of people engaged in jogging,picnics, and baseball games. Americankestrels also have adapted to urbanenvironments where suitable nestingcavities are available (Adams 1994).

The screech owl thrives in somesuburban environments, especiallythose with large wooded lots (Gehlbach1986). Burrowing owls, barn owls, and,occasionally, great horned owls havealso been found in metropolitanenvironments (Adams 1994).Burrowing owls benefit from light levelsof urban development and reach theirhighest densities in areas 55 to 65percent developed. Other population-limiting factors are encountered beyondthat development level, however.

Effects of urbanization onmammals—In general, urbanenvironments support fewer speciesof mammals than surrounding ruralareas (Adams 1994). The species thatoccur in urbanized environments tendto be habitat generalists rather thanspecialists. Urbanized areas can supporthigh populations of exotic species, suchas the house mouse and Norway rat. Inless urbanized areas where large greenspaces remain, more species are likelyto be encountered. Downtown Bostoncemeteries support 20 species ofresident mammals (Bolen andRobinson 1995).

Small and medium-sized mammals,especially granivores, are the mostabundant mammals found in urbanand suburban environments (Adams1994). In one study, mammals found inurban greenspaces were primarilyhabitat generalists that utilize a mosaicof habitat types (VanDruff and Rowse1986). Deer mice, meadow voles, treesquirrels, ground squirrels, chipmunks,and woodchucks are common residentsof urban areas (Adams 1994). Somesmall mammals, however, are habitatspecialists that do not easily adjust tochanges brought about by urbanization.Fragmentation of habitat in the GreatDismal Swamp of Virginia and NorthCarolina by residential subdivisions andindustrial parks may be contributingto the decline of five indigenoussubspecies of mammals (Rose 1991).The Allegheny woodrat is restrictedto only a few habitats and is listed asthreatened in Pennsylvania becauseof statewide declines (Balcom andYahner 1996). Increases in residentialand agricultural development wereobserved near sites of extirpation.The few sites still occupied by thewoodrat generally had less fragmentedsurroundings (agricultural lands)than sites of extirpation.

Large herbivores do not easily findsuitable habitat in highly urbanizedsettings (Adams 1994). Their largebody sizes and correspondingly largehome ranges exclude them from manyurban environments. Nevertheless,many cities in North America havevery high densities of white-taileddeer. Problems with damage to urbanvegetation in sensitive areas, such asflower gardens and parks coupled withhigh instances of deer-vehicle accidents,have prompted some cities to initiatepopulation control activities (Bolenand Robinson 1995).


Small insectivorous mammals, such asshrews, moles, and bats, are commonlyencountered in most residential areas.Suburban residential areas often makeexcellent habitat for medium-sizedomnivores, such as raccoons (Hoffmannand Gottschang 1997), opossums,armadillos, and skunks (Adams 1994).

Red foxes are more tolerant of urbanareas than gray foxes. They occasionallyden in large wooded areas within somelarger cities. Urban foxes are commonin many British cities, even in thedistricts most densely populated byhumans (MacDonald and Newdick1982). In a Boston cemetery, residentred foxes hunt a burgeoning graysquirrel population (Bolen andRobinson 1995). Gray foxes aremore wary of urbanized areas, butcan be found in rural residential areas(Harrison 1997). The threshold foravoidance of residential areas bygray foxes is between 130 and 325residences per square mile. Coyotesare becoming more common in urbanand suburban settings (Adams 1994).Coyotes occur in suburban Seattle andLos Angeles, in residential areas northof New York City, and in Lincoln,NE. In Lincoln, one coyote spentmore than 70 percent of his timein a 35-acre residential subdivision(Bolen and Robinson 1995).

Large predators, such as wolves,cougars, and bears, are not part ofurban mammal communities (Adams1994). They have been eradicated frommost rural areas as well. Black beardistribution in coastal North Carolinais negatively correlated with humandensity and positively correlated withpercent of total forested land (Jonesand others 1998).

Effects of urbanization on reptilesand amphibians—Some amphibiansand reptiles have characteristics thatmake them vulnerable to the effects ofurbanization (Adams 1994). They areless mobile than birds or mammals, anddispersal rates are slower. With habitatfragmentation, many amphibians andreptiles exist in localized distributionsrather than one continuous popu-lation. Urbanization tends to excludespecialized reptiles and amphibians,while species with broad ecologicaltolerances and more general habitatneeds tend to be more successful. Manyreptiles and amphibians are eliminatedwhen wetlands and aquatic habitats arelost due to drainage, channelization, or

filling. Removal of ground cover andunderbrush eliminates habitat for manysalamanders and snakes (Adams 1994).

Amphibians are especially susceptibleto local extirpations and constraintson recolonization due to the shortdistances traveled, site fidelity, andphysiological constraints (Blausteinand others 1994). The effects of foresthabitat loss during urbanization maybe especially severe for forest-dwellingsalamanders. Schlauch (1976) foundthat woodland salamanders, such asthe blue-spotted, spotted, marbled, andeastern tiger salamander, were reducedin distribution in urbanized areas ofLong Island. Loss of ponds, loweredwater tables, urban pollution, reducedamounts of woodlands, and collectionsfor pets were contributing factors.In addition, the northern two-linedsalamander disappeared from mostareas on Long Island due to destructionof suitable springs. This species needscool and flowing spring water tobreed. In western North Carolina, theabundance and diversity of salamanderswere drastically reduced followingclearcutting of the forests (Ash 1997,Petranka and others 1993). There issubstantial debate about the recoveryand long-term stability of salamandercommunities in managed forests (Ash1999, Petranka 1999), but deforestationassociated with urban developmentwould be permanent, with littlelikelihood of recovery for manysalamander species.

Recolonization of suitable areas canalso be problematic for some reptiles,especially those that are habitatspecialists. The Florida scrub lizard is arare endemic, and its largest remainingpopulation is in Florida sand pine scrubon the Ocala National Forest (Tieboutand Anderson 1997). The lizard haslimited vagility and can only occupyyoung seral stages of a regeneratingforest (less than 7 to 9 years of age).Scrub lizards probably do not dispersethrough forests older than about 12years of age. Fire suppression and thelack of forest successional dynamicshave contributed to the rarity ofthis lizard.

The threatened gopher tortoise alsois sensitive to urbanization. Egg andhatchling mortality can be quite highin urban areas (see sections “Effects ofexotic animals on forest wildlife: exoticinsect pests and forest wildlife” and“Effects of exotic animals on forest

wildlife: effects of exotic wildlife onnative forest wildlife”). This problem iscompounded by low reproductive rates(Adams 1994). The gopher tortoise hasbeen extirpated from urban areas inMobile County, AL (Nelson and others1992). Populations are more stable,however, in areas with less severehabitat disturbance. Habitatmodifications and land use changesassociated with urbanization andagricultural development haveeliminated the timber rattlesnake frommuch of its historic range in east Texas(Rudolf and Burgdorf 1997).

Although urbanization excludes somesensitive forest reptiles and amphibians,urban environments may providehabitat for some species. The heavilyurbanized western end of Long Islandstill supported 28 of the 37 speciesdocumented to historically exist onLong Island (Schlauch 1976). The lessdeveloped, eastern end supported 35 ofthe 37 species. Herpetofauna found tobe urban tolerant by Schlauch (1976)included the red back salamander,Fowler’s toad, the brown snake,the garter snake, and the eastern boxturtle. Due to pet collection, box turtlesdisappeared quickly from areas nearany ground-level nature trails, however.

Other general effects ofurbanization on forest wildlife—Many habitats, such as the longleafpine ecosystem or pine-oak woodlandsof the Southern Appalachians, aredependent upon fire for maintenance.Fire suppression has affected the qualityof wildlife habitats in some southernforests. In many forest areas,management now includes prescribedburning. However, the increasingpresence of roads and residentialareas has interfered with the use ofprescribed fire. For more informationon the effects of fire suppression andprescribed burning, see chapters 4 and 25.

For more information about theeffects of air pollution on forest health,see chapter 18. For more informationabout the effects of increasing demandfor timber products on southernforests, see chapter 13.

Effects of Agricultural LandUse on Forest Wildlife

Forest wildlife densities andmovement along the forest/agricultural edge—Forest wildlifespecies differ in their responses toforest/agricultural edges. Some wildlife


TERRESTRIAL

species are limited to forest interiorhabitats and avoid edges. Other wildlifespecies are adapted to edges and forestopenings, or may be attracted to specialhabitats created at forest/agriculturalinterfaces. Small mammal speciesexhibited differing responses at forest/field edges (or forest wildlife openings)(Manson and others 1999, Menzel andothers 1999, Wegner and Merriam1979). Increased numbers ofmammalian nest predators were foundalong forest-field edges (Gates andGysel 1978), higher densities ofmammalian predators were found infloodplain forests adjoining residentialand agricultural land (Cubbedge andNilon 1993), and raccoons were foundto be more abundant in forest edgesadjacent to agricultural fields andstreams (Dijak and Thompson 2000).In contrast, Heske (1995) foundno differences in the abundanceof furbearing and small mammalsalong forest/farm edges versus forestinteriors in southern Illinois.

Nest predation of forest nestingbirds adjacent to agricultural areas—For information about the effects ofsmall forest fragments and forest edgeson the success of forest-nesting birdssee section “Effects of urbanization onforest birds: urban fragmentation andedge effects.”

Some avian species in forests nearagricultural areas have reduced nestsuccess rates. Rates of nest predationfor songbirds were found to beubiquitously high in a study sitebordering agricultural fields. Mam-malian predators (especially raccoons)were abundant throughout the studysite and present on all transectssurveyed (Heske and others 1999).Similarly, higher predation rates forground nests were documented inforests fragmented by agricultural landdue to more abundant avian predators(Huhta and others 1996) and in an areafragmented by agriculture, greaterabundances and species richness ofnest predators (particularly avian nestpredators and snakes), as well as moreabundant cowbirds, were found alongpasture-forest edges (Chalfoun andothers 2002). Increased numbers ofnest predators (crows and blue jays)were noted during bird surveys inthe Great Smoky Mountain NationalPark (Wilcove 1988). Apparently,agricultural and other land conversionsoutside the park boundaries causedan increase of these nest predators,

even in this large, relatively contiguousforest area.

Agricultural areas as habitat forforest wildlife—

■ Early successional species: Manybird species dependent on openhabitats, such as grasslands, prairies,savannas, glades and barrens, are nowin serious decline in the Eastern UnitedStates (Hunter and others 2001a).Today, many of these early successionaland disturbance-dependent species arefound associated with active andabandoned farmland, pastures, andother human forest clearings. Prior toEuropean settlement, these species werefound in naturally occurring andNative-American-maintained forestopenings. Many of these disturbance-maintained ecosystems have been lostfrom the landscape during the last 300years. Some species dependent on themfound suitable nesting habitat inhuman-created fields following loss ofthe natural openings. Populations ofdisturbance-dependent birds and otherwildlife vary along with trends inagriculture. Conversions of pastures tomore intensively cultivated row cropsor intensively mowed, fescue-dominated pastures, the maturing ofabandoned farm fields in some areas ofthe South, and the trend to larger fieldsof cash crops with accompanying lossof fence-row habitat have all affectedearly successional species. Informationfrom the 1997 National ResourceInventory indicates that the 13Southern States lost about 2.2 millionacres of pasture between 1992 and1997, a net loss of about 3.4 percent(USDA Natural Resources Conservation2000). These species are in trouble notonly because of the intensification offarming and declining numbers ofpastures, hay meadows, and abandonedfields, but also due to suppression ofnatural disturbances—fires, beaveractivity, and floods—that generatenatural grass-lands and shrublands(Askins 2001).

The introduction of exotic, cool-season pasture grasses was probably inresponse to overgrazing of native warm-season species and deteriorating rangeconditions (Twedt and others, in press).Use of “improved” cultivars, such astall fescue, red fescue, Bermuda grass,weeping love grass, and many others,began in the mid-1930s. Exotic grasses,such as tall fescue, can be grazed quiteclose to the ground and can be hayed

during the mid-nesting season of manygrassland bird species. Depending ontheir management, intensively grazedor frequently mowed fescue pasturesoffer little or no cover for wildlifeand can be poor habitat for northernbobwhite (Barnes and others 1995)and other grassland species.

Eastern cottontail populations werefound to remain highest in areas withrelatively high amounts of pasture,stable woodlands, hayfields, and fieldsplanted in small grains, such as wheat,oats and barley (Mankin and Warner1999). The presence of pasture seemedto be the most important factor,however. In contrast, increases in rowcrops, such as corn and soybeans, wereaccompanied by declines in cottontails.Pasture environments apparentlymaintained cottontail abundancebecause they are closest to theirpreferred vegetation structure (oldfields and early successional shrublands). Similarly, landscape features,such as percentage of woodland onfarms, percentage of farmland innonrow crops, percentage of land insoil-protecting crops, and percentageof land in conservation tillage, wereused to calculate habitat indices (Ribicand others 1998). These indices areimportant in determining areas likelyto support high populations of northernbobwhites and cottontails. Indicesindicating farming disturbance, such aspercentage of land under grazing andpercentage of land on which fertilizers,pesticides, and herbicides were applied,were associated with lower populations.

■ Importance of vegetated fencerows,hedgerows, and wooded corridors: Thepresence of woody fencerows inagricultural areas provides importanthabitat for many wildlife species (Bolenand Robinson 1995). In areas whereagriculture constitutes a majority of theland use, fencerows with a continuousrow of trees and shrubs can providehabitat for up to 36 species of birds per6.2-mile segment, whereas fencerowswithout woody vegetation support 9or fewer species over the same distance.Forest edges bordered by multiflorarose hedgerows had higher bird speciesdiversity than open forest edges, buthabitat generalists and forest-edgespecies provided most of the increasedbird diversity (Morgan and Gates1982). Forest edges with hedgerowshad more cover in the first 6 feetaboveground level than open forestedges and retained more of this


cover during the winter. In addition,cottontails were also more frequentin forest edges where hedgerowswere present compared to open forestedges (Morgan and Gates 1983).Similarly, farmstead shelterbelts weredocumented to be valuable habitatfor small mammals in agriculturalareas (Yahner 1983).

Vegetated fencerows may beimportant for the movement of somewildlife species, allowing them to reachisolated forest patches across a matrixof open agricultural fields. Chipmunksand white-footed mice tend to movebetween wooded habitats downvegetated fencerows rather thancrossing open fields (Wegner andMerriam 1979). Similarly, many forest-nesting bird species move from onewooded habitat to the next alongvegetated fencerows rather than flyingdirectly across open fields. Even whenwoodland birds, such as eastern pewee,red-eyed vireo, and wood warblers,foraged in open fields, they first movedfrom the woods down fencerows, thenfrom fencerows into the open fields.MacClintock and others (1977)documented that a narrow, disturbedcorridor of grazed woods and earlysecond-growth forest could reducethe isolation of a forest patch, allowingit to maintain a high diversity offorest-nesting birds.

Fencerows in agricultural areas mayhave negative effects on some species,however. Nest survival for loggerheadshrikes in fencerows was documentedto be lower than for those nesting inthe adjoining pastures due to highernest predation (Yosef 1994). Most ofthe potential nest predators observedduring the study either flew or walkedalong fencelines, and appeared to avoidcrossing open pastures. Similarly, area-sensitive grassland bird species avoidednesting in grassy pastures within thefirst 165 feet of wooded fencerows(O’Leary and Nyberg 2000). Sensitivegrassland nesters included twoconservation priority species—Henslow’s sparrow and bobolink.

■ Foraging habitat for forest wildlife:Agricultural areas, including grainfields, pastures, fruit orchards, gardens,and vineyards, are important forageareas for many wildlife species (Martinand others 1951). Not all forage use ofagricultural land by wildlife results in

damage to crops. Foraging byinsectivorous birds and mammals andconsumption of weed seeds by wildlifeis beneficial to agriculture. Wildlifeoften consume waste grain left behindby mechanical harvesting machines orconsume fruit that has fallen on theground. In other cases, however, lossand damage to crops by wildlife havebeen clearly documented. Martin andothers (1951) documented the value ofseveral agricultural commodities forwildlife. Corn is consumed by over 100species of wildlife, including 17 speciesof upland gamebirds, 59 species ofsongbirds, 10 species of fur and gamemammals, 6 species of small mammals,and 3 species of hoofed browsers.Wheat is consumed by more than94 species of wildlife, and oats areconsumed by at least 91 differentspecies. Rice and apples are otherimportant agricultural commoditieseaten by foraging wildlife in the South.

Fallow fields were the mostcommon habitat selected bybobwhite, even though crop fields,wildlife management plots plantedannually in small grain, and woodsmanaged by prescribed burning,were available nearby (Yates andothers 1995). Apparently, insectswere the most important foodresource for feeding bobwhitehatchlings. Insect sampling revealedthat fallow fields had more insectsthan other available habitats.

Black bears in the Southeast feedmore in agricultural areas than in otherparts of the United States, but theiruse of these areas may increase theirvulnerability to hunting, lowering theoverall rates of survival, especially formales (Hellgren and Vaughn 1994).In coastal North Carolina, corn cropdamage by black bears amounted toabout 0.6 percent of the total areasurveyed (Maddrey and Pelton 1995).Most of the damage was within 165feet of the forest edge. In questionnairescompleted by coastal North Carolinafarmers, deer were the major causeof crop depredation (Maddrey andPelton 1995). Crop damage byblack bears, birds, and raccoons wasreported less frequently.

Raccoons frequently use agriculturalareas for foraging. One study foundthat raccoons in an agricultural areaforaged mainly on corn, whichaccounted for up to 76.2 percentof their diet (Sonenshine and Winslow

1972). Coyotes were found to bewell adapted to agricultural areasin Vermont (Person and Hirth 1991).They preferred hardwood forests inthe winter and spring, and farmlandduring the summer and fall.

Great horned owls are habitatgeneralists that prefer open croplandand pastures for foraging (Morrelland Yahner 1994). Barn owls alsoprefer to forage in pastures and grass-dominated agricultural areas (Bolenand Robinson 1995).

Wintering flocks of grackels, red-winged blackbirds, starlings, andbrown-headed cowbirds use fieldsand feedlots for foraging. One suchwintering flock removed 1,300 to7,000 tons of corn each winter from atotal foraging range of about 541,000acres (White and others 1985). In acontrol measure, over 1 million birdswere killed with the surfactant PA-14one winter. Recruitment of birds fromsurrounding areas caused the roostto return to prekill levels withinabout 2 weeks. Roost fidelity for suchwintering flocks averages only 3.5 to4.4 nights per individual. Thus, thedaily population turnover rate forthe roost is about 23 percent.

■ Hazards of agriculture to wildlife:Although agricultural areas are habitatfor many wildlife species, they can alsosubject them to hazards notencountered in natural areas. Mowingequipment and nighttime mowing hasincreased the mortality of easterncottontails, bobwhite, and other wildlifeattracted to pastures and hayfields(Bolen and Robinson 1995).

Many wildlife species forage inagricultural fields, but crop losseshave resulted in lethal and nonlethaldepredation control measures (Bolenand Robinson 1995). Under someconditions, certain crops may beharmful to wildlife. Geese that consumedry soybeans may harm or obstructtheir esophagi as the swelling soybeanscause hemorrhaging and necrosis,or prevent the passage of food to thestomach. Aspergillosis is a fungalinfection of the respiratory tract,contracted by birds exposed to moldingcrops. Once contracted, the infectioncan be spread to other birds, causingsizable die-offs.

Wildlife living and foraging inagricultural areas are exposed toinsecticides, herbicides, and fertilizers


TERRESTRIAL

(Bolen and Robinson 1995). Manyinsecticides are not species-specificand can be lethal to wildlife throughdirect exposure or through ingestionof contaminated prey species. Someof the more toxic pesticides, includingthe chlorinated hydrocarbons DDT,Aldrin, and others, are now bannedin the United States, but because oflong residual times and heavy pesticidebuildups, it has taken some time fortheir deleterious effects to fade. Mostherbicides approved for use todayare not directly toxic to forest wildlifeif applied correctly. Indiscriminant usecan indirectly harm wildlife, however,by reducing important vegetationfor cover and forage. Fertilizers ingranular form can resemble seedsor grit and offer a potential hazardto birds that might ingest a largenumber of granules.

Old field successional areas—Some areas of the South are likely toexperience a reduction in agriculturalland uses with a subsequent return toforest habitat (see chapter 6 for moreinformation). Many of these increasesin forest acres will undoubtedly bein the form of pine plantations ratherthan natural forest types, however(see chapter 13). See chapter 4 for adiscussion of the influence of pineplantations on forest wildlifeand habitats.

Abandoned agricultural land under-goes a series of vegetation changesthat provide important habitat for anumber of wildlife species. The returnto old-field habitat benefits manydisturbance-dependent bird species.Successful management for many ofthese rare and declining birds willrequire adequate space for area-sensitive species, connecting corridorsbetween early successional habitatareas, and availability of areas inspecific vegetation stages to offsetnatural plant succession (Hunter andothers 2001a). Breeding bird densityand species composition shift asabandoned farm fields undergo naturalvegetative succession to mature forests(Johnston and Odum 1956). A fewspecies, such as the cardinal, persistthrough many plant successive stages;but most birds appear to have a definiterange of vegetative stages. Browsingmammals, such as deer, also benefit asabandoned agricultural areas undergo

the vegetative transition into scrub-shrub habitats (Adams 1994).

Old-field habitats can vary invegetative structure. The presenceof exotic vegetation in agriculturalenvironments is an influence thatpersists long after fields are abandoned.Previous types of agricultural usecan influence the vegetative structureand, hence, the wildlife habitat in aparticular abandoned field. Abandonedpastures differed markedly in theirvegetation compared to previouslycultivated old fields (Stover and Marks1998). Exotic herbaceous plants inan old-field environment reached theirpeak abundance within 65 feet of theforest edge (Meiners and Pickett 1999).

Restored bottomland hardwoodforests failed to regain their wildlifehabitat value relative to mature forestseven 50 years after agricultural usage(Shear and others 1996). Althoughthe regenerating forests had similarstructural attributes to the uncutforests, the lack of heavy seeded,mast-producing tree species (oaksand hickories) made them generallyless useful for mast-dependent forestwildlife. Conversely, bottomlandhardwood reforestation efforts thatrely solely on oak planting are slow toproduce a substantial three-dimensionalforest that provides useful habitat fornongame species, including manyneotropical migrants (Twedt andPortwood 1997). More naturallyinvading species became establishedin bottomland hardwood restorationareas sown with acorns than in areasplanted with oak seedlings (Twedtand Wilson, in press).

Other general effects of agricultureon forest wildlife—Agricultural landuses have resulted in fire suppressionand interruption of presettlementforest fire patterns. Lack of fire in mostforest habitats has greatly affected thequality of wildlife habitat. For moreinformation on the effects of firesuppression and prescribed burning,see chapters 4 and 25.

Agricultural disturbance haspermitted introduction of a greatmany exotic plant and animal species.See section “Effects of exotic species onforest wildlife and wildlife habitat” ofthis chapter for information about theimpacts of exotic plant and animalspecies on forest wildlife.

Effects of Linear Land Uses(Roads, Power Lines, andTrails) on Forest Wildlife

Habitat displacement of wildlifeby roads and power lines—Someforest wildlife are excluded from orare less numerous in areas adjacentto roads and highways. Woodlandbreeding birds and terrestrial birdswere found to have reduced densitiesadjacent to highways (Reijnen andothers 1995, Kuitunen and others1998). Some species clearly avoidedthe road, while others appeared tofavor road-forest edges. Birdsresponding to corridor/forest edgesalong a power line corridor could bedivided into edge, deep forest, andunaffected species (Kroodsma 1982).

Road and power line corridors mayvary in their effects on forest wildlife,depending on corridor width. Forest-interior, neotropical migrant birdsexhibited diminished abundancesalong wide power line corridors (50to 75 feet) but not along narrow forestopenings (of 25 feet) along unpaveddirt roads (Rich and others 1994). Suchedge effects may not be as important forbirds nesting in predominantly forestedlandscapes. In a landscape more than70 percent forested, worm-eatingwarblers in small forest patches,separated by paved two-lane roads andhouse lots, were found to have nestingsuccess comparable to those nestingin large forest tracts (Gale and others1997). However, even in heavilyforested landscapes, ovenbirds showedreduced densities of breeding territoriesand reduced pairing success within500 feet of forest roads (Ortega andCapen 1999). Therefore, while edgesof narrow corridors may be acceptablehabitat for some bird species, they maybe unsuitable for others. These issuesmust be evaluated in terms of theconservation concerns for the speciesat issue in a given situation (see chapter4 and section “Effects of urbanizationon forest birds: urban fragmentationand edge effects” of this chapter fordiscussions concerning ovenbirdresponse to edges versus conservationstatus).

Forest roads were found to reducethe abundance and species richness ofmacroinvertebrate soil fauna (Haskell2000). This effect extended up to 330feet into the forest. Although wider


roads and those with a more opencanopy produced steeper declines,even narrow roads through forestsproduced marked edge effects.

Early successional and forestedge habitat—Some wildlife areattracted to roadsides and power linerights-of-way because of grassland,early-successional, or edge habitat.The value of roadsides and utilitycorridors has been documented forgrassland and habitat generalist speciesof small mammals (Adams and Geis1983, Johnson and others 1979).

Corridor width and vegetative charac-teristics influence the attractiveness ofthe habitat for bird species. Road rights-of-way are important habitat for birdsthat nest in edges and ecotones (Warner1992). The number of roadside nestsand species increased with roadsidewidth. Mowing schedules, diversityof vegetation, and vegetative structuralcomplexity affected the habitat valueof roadsides for nesting birds. Narrowpower line corridors (40 feet wide) hada reduced diversity of birds comparedto wider corridors (100 feet or more)(Anderson and others 1977). Widecorridors attracted more grasslandbird species. Power line corridorswith increased patchiness of shrubvegetation, showed increased fledgingsuccess of nesting birds (Chascoand Gates 1992). Fledging successdecreased, however, as the habitatbecame more homogeneous. Manyearly successional and disturbance-dependent bird species can be foundin roadsides and utility rights-of-way(Hunter and others 2001a, Meehanand Hass 1997), but corridors lackingshrub growth may have fewer nestingand wintering birds (Meehan and Hass1997). Corridor nesting birds weremore dense in the corridor interiorsthan along the edge (Kroodsma 1987).

Linear corridors as dispersalbarriers for wildlife—Small forestmammals, such as eastern chipmunks,gray squirrels, and white-footedmice, were found reluctant to ventureonto road surfaces when the distancebetween cleared road margins exceeded65 feet (Oxley and others 1974). Four-lane highways acted as effective barriersagainst the movements of these smallforest mammals. Medium-sizedmammals, such as woodchucks,porcupines, raccoons, and stripedskunks, crossed wider cleared roadmargins more often, but suffered higher

road mortality than small mammals.Similarly, the movements of white-footed mice across roads, includingnarrow gravel roads, were found to beinfrequent (Merriam and others 1989);and paved roads were found to be asignificant barrier to the movementsof woodland mice (Mader 1984). Evensmall forest roads not open to publictraffic were seldom crossed.

The presence of roads appeared tosubstantially hinder the movementsof forest amphibians (Gibbs 1998).In a different study, primary andsecondary roads did not affect thepresence and movement of forestfrogs and toads (DeMaynadier andHunter 2000). The movement offorest salamanders was significantlyinhibited by primary forest roads, butthe minor forest roads had little effect.

Black bears in the Pisgah NationalForest of North Carolina almostnever crossed an interstate highway;roads with low traffic volume werecrossed more frequently than thosewith high traffic volume (Brody andPelton 1989). Bears also appearedto adjust their home ranges to areaswith lower road densities.

The nature of the corridor edgemay determine how strongly thatedge serves as a boundary for wildlife.Abrupt vegetative transition from forestto mowed grass on the edge of a powerline corridor was found to be a barrierto forest birds and served as a naturalterritorial boundary for many birdspecies (Chasco and Gates 1992).When the vegetative contrast of thecorridor was softened by shrubbyvegetation, however, there was greateroverlap between mixed-habitat andforest bird species. Power line corridorswith abrupt edges were also avoidedby small and medium-sized mammalsbecause of difficulties in crossingthe dense grass mats (Gates 1991).Corridors with a wide shrub zonealong the edge had increased useand permeability to movement.

Wildlife underpasses can be aneffective way to relieve the barriereffect of roads for some wildlife species(Clevenger and Waltho 2000). Wildlifediffer in their abilities to utilize under-passes. In south Florida, white-taileddeer, raccoons, bobcats, the endangeredFlorida panther, alligators, and blackbears were all documented to useunderpasses to traverse an interstatehighway (Foster and Humphrey

1995). Considerations for topography,habitat quality, location, and the levelof human activity in the vicinity areimportant in designing a successfulwildlife underpass (Clevenger andWaltho 2000).

Linear corridors as dispersal routesfor wildlife—Road rights-of-way alsocan facilitate the movement of wildlife.Some grassland and early-successionalspecies, such as Bachman’s sparrow,require grassy and shrub-dominatedcorridors to facilitate their movementto and from isolated patches of suitablehabitat (Dunning and others 1995).Meadow voles greatly expandedtheir range in central Illinois afterthe establishment of continuousstrips of dense, grassy vegetationalong interstate highways (Getz andothers 1978). In contrast, the prairievole is not restricted in movement byinterruptions in grassy habitats. Thisspecies remains dominant in grassysites not connected to the interstate,such as pastures and county roadsides.Similarly, a shrubby power line corridorand edges served as travel lanes forred foxes and striped skunks in a frag-mented landscape (Gates 1991); butmammalian nest predator abundancewas found to be influenced by bothlocal and landscape-level features(Dijak and Thompson 2000).

Black bears use roads in the GreatDismal Swamp National Wildlife Refugeas travel corridors through the densepocosin vegetation (Hellgren and others1991). Such road use by bears is morecharacteristic among “unharvested”or protected populations. Hunted bearpopulations generally avoid roads,especially those with unrestricteduse by humans.

Wooded roadside corridors serve astravel lanes for native forest mammals,but use of corridors taper off withdistance from the forest (Downes andothers 1997a and 1997b). Woodedroad corridors appear to be usedheavily by nonnative house miceand black rats, reducing their valueas a remedy for habitat fragmentation.Males of some mammal species mayutilize corridor habitats in greaternumbers than females, indicatingthat roadside forest corridors mayfunction as intraspecific filters.

Road mortalities and forestwildlife—Mortality along roads andhighways has been well documented


TERRESTRIAL

for many species of wildlife, but anumber of factors influence the severity,including season, weather events,type of road, location of road, androad density. During a 14-monthperiod along a dual-lane highway,road mortalities were documented for11 species of mammals, 12 species ofbirds, 5 species of reptiles, 9 speciesof amphibians, and insects belongingto 11 orders (and more than 249different species) (Seibert and Conover1991). Amphibian mortalities werehigher in certain seasons and afterrains. Populations of timber rattle-snakes were reduced in areas of easternTexas having high road densities(Rudolph and Burgdorf 1997). Road-related mortality was a significant threatto raptors, especially northern saw-whet owls and eastern screech owls(Loos and Kerlinger 1993); but road killnumbers varied with season, location,road type, and species involved.

Mortality rates of small forestmammals, such as Eastern chipmunks,gray squirrels, and white-footed mice,were highest when cleared roadmargins were about 45 to 115 feet(Oxley and others 1974). Mortalityrates for these small mammals droppedas cleared margins grew wider, mainlybecause they seldom attemptedcrossings of wider forest clearings.Mortality of medium-sized mammals,such as woodchucks, porcupines,raccoons, and striped skunks, increasedwith increased cleared width, reachinga peak when traffic density was highand young were emerging. Smallmammal road mortalities on interstatehighways was found to be greatestfor species with highest densities inthe right-of-way habitat, but the lossdid not appear to be detrimental topopulations of these species (Adamsand Geis 1983). Road mortalitiesfor white-tailed deer along interstatehighways have been documented byReilly and Green (1974) and Puglisiand others (1974). Road mortality ofvertebrates were recorded in northFlorida (Cristoffer 1991). Mortalityincreased with increasing speed limitsand increasing density of roadsidevegetative cover.

Population impacts of road-inducedmortality can be significant for somewildlife species. In south Florida, roadkills are the largest source of human-induced mortality for the endangeredFlorida panther and the endangered

Key deer (U.S. Fish and WildlifeService 1999).

Spread of exotic plants andanimals—Roads and power linecorridors provide habitat andmechanisms for the spread of someexotic plants and animals. All high-and low-use roads sampled in anexperimental forest contained at leastone exotic plant species, some had asmany as 14 (Parendes and Jones 2000).Even abandoned spur roads with notraffic over the last 20 to 40 years stillhad numerous exotic plants. Narrow,linear forest openings associatedwith roads and power lines appearconducive to establishment of thered imported fire ant (Stiles and Jones1998). See the review in Trombulakand Frissell (2000) and the informationcompiled by the National ResourcesDefense Council (2000) for moreinformation about the spread of exoticplants and animals along roads.

Other effects to wildlife from roadsand power lines—Roads can providehunters and poachers with increasedaccess into forested areas (NaturalResources Defense Council 2000).Many large mammals are exposedto increased hunting pressure nearroads, and some may have difficultiesmaintaining their populations nearroadsides. In the AppalachianHighlands, management of black bearsrequires a special concern for roaddensity (Clark and Pelton 1999). Whileoverall black bear populations in theSouthern Appalachians are consideredstable to increasing at the presenttime, most black bear mortality ishuman-induced and includes hunting,poaching, and road kills. Huntingand poaching efficiencies increasealong with improved vehicle access,and black bear habitat suitability isincreased when the density of roadsis kept low or if logging roads areclosed after the timber has beenharvested (Clark and Pelton 1999).Similarly, Brody and Pelton (1989)concluded that the primary effectof roads in bear habitat in westernNorth Carolina was an increase inthe vulnerability of bears to hunting.

Roads can subject wildlife toincreased levels of heavy metals,salts, and organic compounds throughaccumulation in plants, soil, and water(see the review in Trombulak andFrissell 2000). Corridor maintenanceby mowing presents a hazard for some

ground-nesting birds and other wildlifespecies (Bolen and Robinson 1995).

For a discussion of indirect effects ofroads, including promotion of furtherhuman land use changes, see the reviewin Trombulak and Frissell (2000).

Effects of trails on forest wildlife—The effects of trails appear to be betterdocumented for plants than othertaxa. Trampling by hikers and otherforest recreational users has beenimplicated in the decline of sensitiveforest understory plants (Gross andothers 1998).

Research from regions outside of theSouth has documented shifts in forestbird composition along trails (Hickman1990, Miller and others 1998, Van derZande and others 1984). Such effectsmay depend on the intensity and timingof the recreational disturbance, however(Van der Zand and others 1984).

In other more general studies,research indicates that human intrusioncan alter bird behavior and communitystructure. Disturbance by pedestriansand vehicles was found to reduce thenumber of bird species on woodedstreets, as well as species persistence,guild density, and probability ofoccupation by individual bird species(Fernadez-Juricic 2000). Crows werefound to be more vigilant in areasof high human disturbance thanin areas of low human disturbance(Ward and Low 1997). Since vigilanceand foraging are mutually exclusivebehaviors, the level of human activitycan affect the foraging success ofsensitive bird species. Others havefound, however, that low levels ofhuman intrusion (one person for 1 or2 hours per week) did not significantlyaffect the vertical distributions of anyforest bird species in three vegetationstrata above the ground (Gutzwiller andothers 1998). The forest bird speciesstudied were apparently able to toleratelow levels of human intrusion.

Black bears also are sensitive tohuman disturbance and may be affectedby the presence of trails. Hibernatingblack bears were found to readilyabandon their dens and cubs inresponse to investigator disturbance(Goodrich and Berger 1994).

As observed by Schlauch (1976),some “collectable” wildlife, such asbox turtles or salamanders, disappearquickly in the vicinity of ground-levelnature trails due to pet collection.


Not all wildlife are disturbed orexcluded by trails. Mammalian nestpredators, including raccoons, skunks,and coyotes, were observed to becommon along trails (Miller and others1998) and seem to be abundant inedge habitats (Gates and Gysel 1978).

Discussion andConclusions

Effects of Exotic Plantsand Animals

Exotic forest pests, including insectsand plant pathogens, have changedthe structure of some forest types, andchanged the density and compositionof wildlife associated with them. Exoticplant species have also displaced nativeforest trees and understory plants insome areas, but the resultant effectsto forest wildlife are not well described.Exotic plants have been introducedto enhance wildlife habitat, but theirindiscriminant use in the past has ledto serious invasions. Exotic animalshave harmed some forest wildlife bydisplacing native species, preying onnative wildlife, or damaging sensitiveforest habitats. Only a small percentageof exotic species (4 to 19 percent)have been documented to cause greatharm. Another 6 to 53 percent haveneutral effects or their effects are notas yet documented.

A large number of potentially invasiveexotic species can impact native wildlifeand their habitats in the United States.New plant species continue to beimported. Approximately 6,741 plantspecies are recognized as weedselsewhere in the world. Only 2,363occur in the contiguous United States(Westbrooks 1998). In addition, anestimated 26,000 plant species arecapable of becoming invasive once theyare introduced into new environments(Campbell 1997). Approaches havebeen recommended for betterpredicting the invasive potential ofexotic plant species (Mack 1996). Theyinclude simultaneous field comparisonsbetween cogeners, one naturalized andone native, and following the fate of aspecies deliberately sown in a naturalcommunity beyond its current range,with or without environmentalmanipulation. Predictions maybecome better if several approachesare combined simultaneously.

Many of the most invasive plantspecies across the nation are stilloffered for sale (Campbell 1997).This is especially true for invasiveforest exotics. About 67 percent ofinvasive forest vines, including kudzu,are still available for purchase alongwith about 90 percent of the mostinvasive forest trees. Federal and Stategovernments have no unified policyfor limiting entry, reacting to emergencyimportation threats, or fosteringintegrated control methods (Miller1997). No regional agency or organ-ization has clearly defined responsibilityor jurisdiction to organize regionalintegrated weed management programs.Exotic pest plant councils have beenformed in an attempt to address thisgap, and various Federal agencieshave formed the Federal InteragencyCommittee for Management of Noxiousand Exotic Weeds. Control of exoticplants is further complicated by thefact that much of the forest land inthe Southeast is privately owned.Less than 18 percent of forested landin the Southern Appalachians ispublicly owned (SERAMBO 2000).

Many experts have publishedrecommendations for dealing withthe issue of exotic plants and animals(Campbell 1997, Miller 1997, Stein andFlack 1996). Recommendationsinclude:

■ Development of more effective waysto prevent new introductions.

■ Early detection and eradicationof new exotics.

■ Better control and managementof established invaders.

■ Protection and recovery of nativespecies and ecosystems.

■ Better public education and supportfor controlling exotics.

■ Better integration of control effortson the part of responsible governmentand nongovernmental entities.

■ Support for research aimed atidentifying invasive species that couldpotentially damage our forests.

■ Support for further researchaimed at developing effective waysto control exotics.

Effects of UrbanizationUrbanization has resulted in the

loss of forest habitat and fragmentationof forested landscapes. These habitatchanges have had the greatest

detrimental impacts to specializedforest wildlife species with narrowhabitat requirements. Habitatgeneralists have been better able toadjust to changes brought about byurbanization. Based on the currenttrends of urbanization across the South,it is likely that forested habitats willcontinue to be permanently altered,and the amount of available foresthabitat will decrease in some areas.Increasing urbanization changes thespecies diversity, overall abundance,and, more importantly, shifts thespecies composition of forest wildlife.Some forest wildlife species areespecially sensitive to fragmentation,forest edges, and human disturbance.Some species disappear from forestareas even with light levels of urbanintrusion. Other species have lost thekind of early successional or quality-disturbed habitats that they require.

For species with area sensitivities,those that require forest interior, thosethat require specialized habitats, andthose intolerant of human disturbance,special management considerations willbe needed as urbanization increases inareas of the South. Some species willlikely require forest conservation areaswith thousands of acres of contiguoushabitat to be successfully conserved.Protection may be needed to limitroads and human disturbance in theseareas. Barring the feasibility of thisconservation approach, finding severaladjoining larger tracts or areasconnected by corridors may be thenext best alternative. To conserveforest wildlife species dependent onearly successional habitats, forestrymanagement strategies should beformulated to provide a constantavailability of these habitats andprovide connective corridors forlow-vagility species.

With these considerations in mind,urban wildlife habitats will remainimportant for some wildlife species assuitable forest habitats decline in someurbanizing areas of the South. Urbanwildlife preserves should be plannedwith the realization that size, habitatcomposition, connectivity, forestdynamics (management needs), andhuman perceptions of the preservewill ultimately affect the variety andcomposition of the species conservedthere. Innovative designs in smallconservation areas may be needed


TERRESTRIAL

to avoid creating “ecological traps”for ground-nesting birds.

Effects of AgriculturalLand Uses

Agricultural land uses haveinterrupted the continuity of southernforests, and created forest islands.Wildlife differ in their response tothe resulting fragmentation. For somespecies of birds and small mammals,the forest/agricultural boundary actsas a barrier to movement, fragmentingand isolating populations. The presenceof woody, vegetated fencerows mayhelp to facilitate movement of somewildlife, however. Some long distancemigrant bird species and speciesthat nest in forest interiors appearto be adversely affected by forestfragmentation particularly in heavilyfragmented landscapes with low overallforest cover. The presence of nearbyagricultural areas has been shownto reduce the nesting success ofsome forest bird species. Othertaxa of wildlife also exhibit a species-specific response.

Many bird species dependent onopen habitats, such as grasslands,prairies, savannas, glades and barrens,are now in serious decline in theEastern United States. Agriculturalareas, especially grasslands and fallowfields, provide habitat for some ofthese early successional birds and otherwildlife, such as eastern cottontails andquail. The presence of vegetatedfencerows may further enhance thevalue of agricultural habitats for somewildlife species while decreasing thevalue for some grassland species.

Forest wildlife species utilizeagricultural areas as foraging habitat.Foraging wildlife can be beneficial foragriculture when they consume insects,mice, or weed seeds. Consumption ofcrops can also be relatively harmlesswhen it involves consumption ofwaste grain left behind by mechanicalharvesters or consumption of fallenfruit. Still, damage to crops andconsumption of agricultural com-modities is an important issue, andhas resulted in some wildlife speciesbeing subjected to lethal and nonlethaldepredation control measures. Theattraction of wildlife to agriculturalareas has also subjected them to injuryand death due to faster, more powerfulfarm machinery, pesticides, and thedangers of other injury and disease.

Old-field successional habitats areimportant for some wildlife species,but may also serve as introductionpoints for exotic vegetation into theforest, especially along the edges offorest fragments (Brothers and Spinarn1992). The former agricultural landuse may affect the vegetative structureof the resulting old-field habitat, andrestoration to full utility as habitatfor forest wildlife may not occur evenafter a number of years.

Government programs that encouragethe removal of land from intensivecultivation, the establishment of stableground cover for soil conservation,and the deliberate creation of wildlifehabitat areas in predominantlyagricultural environments cangreatly influence the abundanceof and diversity of wildlife species(Bolen and Robinson 1995).

Effects of Linear LandUses (Roads, Power Lines,and Trails)

The effects of roads and power linecorridors on forest wildlife are speciesdependent. For some forest wildlife, thecorridors exclude or result in avoidanceof the area for distances of 330 feetor more. For grassland and early-successional forest species, roadsidesand power line rights-of-way providevaluable habitat, but the value isinfluenced by the width of the corridor,the nature of the corridor vegetation,maintenance practices in the corridor,and the abruptness of the forest edge.For some forest wildlife species, roadsand power line corridors act as barriers,fragmenting populations. Corridors canalso act as intraspecific filters, allowingmovement of a certain age class orgender. For other species, corridorsact as travel lanes, connecting isolatedareas of habitat. Unfortunately, roadsand power line corridors can also actas travel lanes for the spread of exoticplants and animals. Road mortality formany species of forest wildlife has beenwell documented. Speed limit, roadtype, width of the cleared corridor,and other factors affect the mortalitylevels found on a given highwaysegment. Roads also have other effects,including mortality due to increasedaccess by legal and illegal hunters,increased pollution along roadsides,and accelerated land use changesalong roads.

Wildlife and plants can be affectedby the presence of trails through theforest. Trampling by hikers and otheroutdoor recreationists have been foundto cause declines in some sensitiveplant species. In addition, shifts inforest bird composition have beendocumented along trails. Other wildlife,such as bears, are sensitive to humandisturbance and may avoid trails.“Collectable” wildlife species may beextirpated from the vicinity of trailsdue to pet collection.

Needs for AdditionalResearch

Effects of Exotic Plantsand Animals

The effects of exotic plant invasionson forest wildlife remain poorlydocumented. Much of the informationavailable is based on land-managerobservations or expert opinions.There is a need for more scientificinvestigations to systematicallydocument how southern forest wildlifecommunities on both local and regionalscales are affected when forests areinvaded by exotic plant species.“Early-warning” research is neededto identify potentially invasive forestexotics to better guide quarantineefforts. Research is needed to developmore effective control and managementtools for exotic plants and animals.

Human Land Use ChangesThe effects of urbanization and

agriculture are better understoodfor birds than other taxa of forestwildlife. More studies that take placein agricultural and urbanizing areasof southern forests would allowcomparisons with avian speciesstudied in other areas of NorthAmerica. Species responses maydiffer across their respective ranges.

More information is needed aboutthe effects of land use changes onmammals, herpetofauna, andinvertebrates in southern foreststo identify species likely to beadversely affected by urbanization.

More studies are needed that docu-ment which species are most likely tobenefit from connective corridors usedto overcome the deleterious effects offragmentation. More research is neededto determine if corridors have adverse


impacts on forest habitats and toidentify circumstances under whichadverse impacts should be expected.

More information is needed aboutthe breeding success of ground- andlow-nesting forest birds in smallpreserves. Information is neededto formulate management strategiesthat avoid the creation of “ecologicaltraps” for breeding birds.

Linear Land Uses (Roads,Power Lines, and Trails)

Relatively little data on the effects ofroads and power lines on forest wildlifeare available for amphibians, reptilesand invertebrates. More informationspecific to wildlife in southern forestsis needed to allow for behavioraldifferences from one part of a speciesrange to another.

The effect of forest trails on wildlifeis better documented for plants thanother taxa. More information is neededabout wildlife in southern forests.

Acknowledgments

I thank Chuck Hunter, Noreen Walsh,and Lee Barclay of the U.S. Fish andWildlife Service for their reviews andhelpful suggestions. In addition, I amgrateful to the anonymous reviewersfor their critique and suggestions.

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The USDA prohibits discrimination in all its programsand activities on the basis of race, color, national origin,sex, religion, political beliefs, sexual orientation, ormarital or familial status (Not all prohibited bases applyto all programs). Persons with disabilities who requirealternative means for communication of programinformation (Braille, large print, audiotape, etc.) shouldcontact the USDA's TARGET Center at 202-720-2600(voice and TDD).

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In: Wear, David N.; Greis, John G., eds. 2002. Southern forest resourceassessment. Gen. Tech. Rep. SRS-53. Asheville, NC: U.S. Departmentof Agriculture, Forest Service, Southern Research Station. 635 p.

The southern forest resource assessment provides a comprehensiveanalysis of the history, status, and likely future of forests in the SouthernUnited States. Twenty-three chapters address questions regarding social/economic systems, terrestrial ecosystems, water and aquatic ecosystems,forest health, and timber management; 2 additional chapters provide abackground on history and fire. Each chapter surveys pertinent literatureand data, assesses conditions, identifies research needs, and examinesthe implications for southern forests and the benefits that they provide.

Keywords: Conservation, forest sustainability, integrated assessment.

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