Grassland Bird Monitoring at

Jenner Headlands

Estero Americano Preserve

Grassland Bird Monitoring at the

Jenner Headlands 2010 - 2011 and the

Estero Americano Preserve in 2011

January 2012

Ryan DiGaudio

rdigaudio@prbo.org

PRBO Conservation Science

3820 Cypress Dr. #11

Petaluma, CA 94954

www.prbo.org PRBO Contribution No. 1860

the

2011

Table of Contents

Introduction and Background ......................................................................................................... 1

Methods .......................................................................................................................................... 2

Point Count Surveys .................................................................................................................... 2

Vegetation Surveys. .................................................................................................................... 4

Statistical Analysis ....................................................................................................................... 5

Results ............................................................................................................................................. 7

Avian Community ........................................................................................................................ 7

Breeding Status ........................................................................................................................... 8

Special Status Species Occurrence.............................................................................................. 9

Vegetation ................................................................................................................................. 10

Vegetation and Bird Abundance Correlations .......................................................................... 10

Discussion...................................................................................................................................... 11

Acknowledgements ....................................................................................................................... 16

Literature Cited ............................................................................................................................. 17

Figures. .......................................................................................................................................... 21

Tables. ........................................................................................................................................... 28

Appendices .................................................................................................................................... 31

1

Introduction and Background

Many grassland bird species have experienced significant declines throughout the United States

(Peterjohn and Sauer 1999, Brennan and Kuvlesky 2005). In California, declines of grassland

birds have been attributed to the loss, degradation, and fragmentation of grassland habitat to

urban sprawl and agricultural development (Johnson and Schwartz 1993, CPIF 2000, Gennet

2007). Additionally, remaining grassland ecosystems are impacted by non-native plant species

and changes in grazing and disturbance regimes (CPIF 2000, Gennet 2007). While there is

acknowledgment of grassland bird declines, there have been relatively few studies on grassland

birds on the west coast (Gennet 2007, Rao et al. 2008).

In December 2009, the Sonoma Land Trust (SLT) purchased the 5,630 acre coastal Jenner

Headlands property to protect the natural and cultural resources from subdivision and private

development. The property is a mix of coniferous forest (3,137 acres), coastal scrub and

chaparral (678 acres), oak woodland (185 acres), and grassland (1,628 acres), much of the latter

consisting of a 1190 acre coastal prairie on western portion of the property. The SLT has

developed an Integrated Resource Management Plan for the property, which includes using

livestock grazing in the grassland habitat on the property as a tool for vegetation management,

with the goal of maintaining or enhancing habitat quality for grassland-dependent species,

including birds.

Beginning in 2010, PRBO Conservation Science began monitoring the grassland bird population

at the Jenner Headlands with the objectives of acquiring baseline data on Jenner Headland’s

grassland bird population and also to help inform the SLT’s resource management plan for the

property. In 2010 and 2011, we (PRBO) conducted breeding season point count surveys

throughout a 1190 acre grazed coastal prairie grassland on the west side of the property. In

2010, the adjacent ungrazed Sonoma Coast State Park was also surveyed as a means to

evaluate the potential effects of grazing on grassland birds. Although the ungrazed state park

grassland supported a higher proportion of native perennial grasses, we found that the more

2

disturbed, grazed Jenner Headlands supported a higher diversity and abundance of grassland

birds, a result that suggests livestock grazing in mesic coastal prairie habitat such as the Jenner

Headlands may benefit certain grassland bird species (DiGaudio 2010).

But how does the Jenner Headlands grassland bird community compare with similar coastal

grasslands grazed at different intensities? To help answer this question we conducted a second

year of point count surveys in 2011 at the Jenner Headlands in conjunction with point count

surveys at the Sonoma Land Trust’s Estero Americano Preserve, a site supporting 127 acres of

coastal prairie habitat located about 12 miles south of the Jenner Headlands. Unlike the Jenner

Headlands, which has been continuously livestock grazed for more than 120 years, recent

grazing at the Estero Americano has been relatively less intense. Though grazed more or less

continually since at least the 1930’s through 1997, no grazing occurred (except for the

occasional trespassing cow) at the Estero property between 1997 and 2010; prescribed grazing

(12 cow/calf pairs and 8 yearlings) was recently applied between March and August of 2010 as

a habitat management tool to help control invasive plants and promote native flora (S. Wright

pers. com.). This report summarizes results from the 2011 Jenner Headlands and Estero

Americano grassland bird surveys, with some comparisons made between the 2010 and 2011

Jenner Headlands bird survey results. Additionally we report on the bird use of small grassland

patches in the forested interior of the Jenner Headlands property.

Methods

Point Count Surveys. Standardized point count surveys are an efficient method for estimating

the relative abundance, richness and diversity of a bird community (Ralph et al. 1993). In 2010

point count survey stations were established at 66 randomly chosen locations throughout the

contiguous 1190 acre grassland at the west side of the Jenner Headlands property, where

points were evenly distributed 250-300 meters apart from each other and ranged in elevation

from approximately 200 – 1,100 ft above sea level (Figs. 1 and 2); random point locations were

generated using ArcMap GIS software (Hawth’s Tools extension) and were subsequently

ground-truthed to ensure they were appropriately located in grassland habitat. Using the same

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methodology, nine point count stations were established in 2011 at the Estero Americano

Preserve, hereafter referred to as the Estero Americano (Fig. 3). Point count stations at the

Estero Americano ranged in elevation from approximately 70 – 400 ft above sea level. All point

count stations were surveyed three times during the breeding season, where survey visits

occurred twice in May (at least 10 days apart) and once in early June (Table 1). Surveys began

15 minutes after local sunrise and were completed within 4 hours of the start time. The

stations at the Jenner Headlands were grouped into 6 transects, in which each transect

contained between 9 and 15 stations; the arrangement of stations groupings for the transects

allowed for one observer to complete a given transect within a single morning of surveys. All

birds seen or heard at each station were recorded during a 5-minute sampling period, during

which each individual bird was recorded as a separate observation. Each bird detection was

classified according to the type of detection (visual, song or call) and by exact distance from the

observer in meters. Distance to each bird detection was determined using laser range finders.

Birds flying over were recorded as “flyover” and were not ascribed a distance. More specifics

about the PRBO point count method can be found at

http://data.prbo.org/cadc2/index.php?page=songbird-point-counts. All point count data was

entered online at the California Avian Data Center, or CADC (http://data.prbo.org/cadc2/) and

has been made password protected. Access to the data and various data summary tools may

be granted by requesting permission from the author and by registering for a CADC account

through the above URL.

Interior Grassland Area Search Surveys. Area search surveys were used to inventory bird use at

six grassland plots in the forested interior of the Jenner Headlands property. Area searches

comprise of 20-minute “searches” in which the observer could move around in predetermined

area search plots (Ralph et al. 1995). The area search method is preferable to point counts in

relatively small areas, and offers the advantage of being able to move around to flush out

silent, skulking birds. The six interior grassland plots, which ranged in size between 11.2 – 33.9

acres and elevation between 300 ft – 2,000 ft, were isolated from one another by surrounding

forested habitat (Fig. 1 and Table 2). We surveyed four of the six area search plots 3 – 4 times

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throughout the breeding season, where surveys were spaced apart at least 10 days from each

other (Table 2); two of the plots were only surveyed once because after the first survey we

judged it improbable that these sites would ever support grassland birds given their isolation,

small patch sizes and location.

For both point count and area search surveys, we noted evidence of breeding for each species.

We considered a species a confirmed breeder if at least one of the following were observed:

nest found, distraction display, copulation, feeding young or fledglings, and food or fecal sac

carries. We considered a species a likely breeder if observed exhibiting breeding behavior

(singing, paired, courtship and/or territorial behavior) on ≥ 2 visits during the breeding season ≥

10 days apart. Birds were considered potential breeders if observed singing or exhibiting

breeding behavior in suitable habitat only 1 time during the breeding season.

All incidental observations (observations made apart from standardized surveys) were also

recorded, including species seen on the property outside of the breeding season or in non-

grassland habitat. These incidental observations were included in the species list for the Jenner

Headlands property but were kept separate from analyses.

Vegetation Surveys. Grassland vegetation and habitat features were quantified to characterize

the habitat surrounding each point count station using a modified relevé method. The relevé

method described by Ralph et al. (1993) was originally conceived of to assess forest habitat,

thus we modified the standard relevé approach to make it more suitable for characterizing

grassland habitat. Grassland plant species composition was assumed to be generally uniform

around each station for up to 100 m, however estimating the percent cover of each plant

species within such a large area is extremely difficult and prone to observer bias. Therefore, we

sampled three 10 m relevé subplots for each station, in which the 10 m subplots were located

50 m away from the station and spaced 120° apart from each other relative to the station. In

order to randomize how the subplots were oriented relative to the station, we spun a compass

dial and chose the bearing the compass arrow landed on for the first subplot location; the two

5

remaining subplots were oriented 120° relative to the first bearing. For each relevé subplot, we

estimated the percent cover of seven cover types: graminoids (grass, sedges, and rushes), forbs,

shrubs, trees, thatch, rocks, and bare ground. Within each of the three vegetation cover types,

we estimated the percent cover of individual plant species. We also estimated the average

height of graminoids, forbs, and shrubs separately, while ignoring exceptionally tall outlier

individuals not representative of the overall average height. If there were individual plants

exceptionally taller than the average height, we would separately record the species and

average height of that particular species (e.g. 2 m tall poison hemlock in a plot with an average

forb height of 0.5 m). All relevé data were conducted during the breeding season in June and

early July, a time during which most grasses and forbs at the study site were flowering and thus

identifiable. All vegetation variables were measured from the Jenner Headlands in 2010 and

from the Estero Americano in 2011. At the Jenner Headlands in 2011, we repeated subplot

relevés for a subset of the point count stations, while repeating data collection at all point

count station subplots for grass height, percent bare ground cover, and percent cover of two

invasive grass species of possible management concern (Nassella manicata and Holcus lanatus).

Statistical Analysis

Point Counts. We calculated the abundance of all species, where abundance equals the average

number of individuals detected from each point count station. We standardized detection

rates by only including detections within 100 m of the observer for analyses, thus assuming that

detection probabilities in grassland habitat were similar within this distance. Excluding

detections that were beyond 100 m also excluded most non-grassland bird species associated

with the adjacent coastal scrub and forest habitats. We focused our analysis on the abundance

of the four most common species: Grasshopper Sparrow and Savannah Sparrow, the two most

common grassland birds found at both study sites, and Song Sparrow and White-crowned

Sparrow, two coastal scrub associated species that were also common at both study sites.

6

We compared abundance indices of these four focal species from the Jenner Headlands

between years (2010 and 2011), and also between study sites (Jenner Headlands and the Estero

Americano in 2011). The distribution of the abundance data was non-parametric and right

skewed (i.e. many zero values and few high values), therefore we used box plots to graphically

represent each species’ abundance, and we used one-way Monte-Carlo permutation tests to

test for significant differences (R Development Core Team 2008).

Count data coupled with distance is known as “distance sampling”, a method that, with a

sufficient sample size, allows for estimates of densities rather than relative abundance (Thomas

et al. 2002). For Grasshopper Sparrow and Savannah Sparrow, we estimated their 2010 and

2011 density at Jenner Headlands in program DISTANCE, version 6.0, release 2, using the half-

normal detection model with cosine adjustments and a multiplier for multiple site visits within

a year (Thomas et al. 2010). From these analyses, we report the estimated density (birds per

acre) with 95% confidence intervals, the detection probability, and the coefficient of variation

(standard error/estimated density). Our sample size was not large enough to calculate the

Estero Americano bird densities using DISTANCE.

Vegetation. To examine relationships between vegetation and grassland birds, we calculated

Spearman’s rho correlation coefficients (a non-parametric measure of dependence between

two variables) between pre-selected (a priori) vegetation variables and the relative abundance

of Grasshopper Sparrow and Savannah Sparrow. The vegetation variables selected were

graminoid cover, grass height, and the cover of Holcus lanatus and Nassella manicata, two

exotic grasses of potential management concern. In 2010, we found that grass height was

highly correlated with residual dry matter (RDM) across the landscape; therefore we assume

grass height to be an indicator of relative grazing intensity (DiGaudio2010). To examine if

grazing intensity at Jenner Headlands was different in 2011 compared to 2010, we compared

the average grass height using two-sample t-tests (R Development Core Team 2008).

7

Results

Avian Community. A total of 114 bird species were detected at Jenner Headlands in 2010 and

2011 combined; this includes observations from point counts, area searches, and incidental

observations from outside the breeding season (Appendix A). From the Estero Americano

Preserve, we detected a total of 44 species during the breeding season of 2011 (Appendix B).

The greater number of species found at the Jenner Headlands is largely explained by the Jenner

Headland’s much larger size (5,630 acres vs. 127 acres) and the greater diversity of habitat

types and respective bird communities supported by those habitats. Many of the species found

at Jenner Headlands that were not at the Estero Americano were species associated with the

former’s mixed evergreen forest habitat that the latter does not have (e.g. woodpeckers and

warblers). Another contributing factor for the greater number of species observed at the

Jenner Headlands is simply that much more field time and effort has been logged at the Jenner

Headlands from 2010 and 2011 than at the Estero Americano, which was only surveyed in 2011.

While the overall number of species observed between the Jenner Headlands and the Estero

Americano may not be directly comparable, we can compare the grassland bird communities

between the two sites. At both sites, Grasshopper, Savannah, Song, and White-crowned

sparrows were among the most abundant species (Table 3). Savannah Sparrow was the most

common bird at the Jenner Headlands grassland with an average of 2.12 birds per point count

station in 2011, whereas Grasshopper Sparrow was the most common bird at the Estero

Americano with an average of 2.00 birds per point count station (Table 3). There were

significantly more Grasshopper Sparrows per point count station at the Estero American than at

Jenner Headlands in 2011 (Monte-Carlo permutation test p <0.05), however the difference in

abundance among Savannah, Song, and White-crowned sparrows between the two sites was

not significant (Fig. 4).

The Jenner Headlands supported two grassland bird species that were not found at the Estero

Americano- Horned Lark and Lark Sparrow. Both of these species, however, occurred at very

low densities. Lark Sparrow abundance was 0.18 and 0.09 birds per point count station in 2010

8

and 2011, respectively, whereas the property’s entire nesting population of Horned Lark was

probably restricted to 1-2 pairs in both years. For both years, one Horned Lark pair occupied

the same territory, which consisted of a patch of rocky, sparsely vegetated serpentine soil.

In comparing interannual variation at the Jenner Headlands, there were significantly fewer

Grasshopper Sparrows in 2011 than in 2010 (Monte-Carlo permutation test p=0.01), whereas

there was not a significant difference in abundance for Savannah, Song, and White-crowned

Sparrows (Fig. 5). In fact, Grasshopper Sparrow dropped from being the second most abundant

species in 2010 (after Savannah Sparrow) to the fifth most abundant species in 2011 (Table 3).

A closer inspection of Grasshopper Sparrow abundance by each survey visit revealed that their

numbers increased with each visit in 2010, however their numbers remained stable throughout

the 2011 surveys (Fig. 6).

At the Jenner Headlands, where we had a sufficient sample size to use the program DISTANCE

to calculate density with point count data, Grasshopper Sparrow density in 2010 was estimated

to be 0.10 birds per acre, which extrapolates to 116 birds in the 1190 acre grassland (Table 4).

In 2011, Grasshopper Sparrow density was estimated to be just 0.04 birds per acre, or a total of

53 birds, roughly half the number of birds from the previous year. Savannah Sparrow density

was similar in both years, where it was estimated to be 0.39 birds per acre (467 individuals) in

2010 and 0.34 birds per acre (408 individuals) in 2011 (Table 4).

Interior Grasslands. From the interior grassland area search surveys, we detected a total of 38

bird species, which were predominantly forest and oak woodland associated bird observed

using the edges of the grassland patches (Appendix D). Though we detected species associated

with oak savannah habitat (e.g. Oak Titmouse, Lesser Goldfinch, Western Bluebird), we did not

detect any true grassland birds such as Grasshopper or Savannah Sparrows.

Breeding Status. At the Jenner Headlands we confirmed breeding for 15 species, which were

Wild Turkey, Red-tailed Hawk, Great Horned Owl, Western Scrub-Jay, Common Raven, Violet-

9

green Swallow, Rock Wren, Western Bluebird, European Starling, Lark Sparrow, Song Sparrow,

Savannah Sparrow, and Grasshopper Sparrow, White-crowned Sparrow, and House Finch

(Appendix A). An additional 49 species were considered probable breeders, and 21 additional

species were considered potential breeders, the majority of which represent species associated

with the surrounding scrub and forest habitats (Appendix A).

At the Estero Americano, breeding was confirmed for Grasshopper Sparrow, Savannah Sparrow,

and Western Scrub-jay. Twenty additional species were considered likely breeders and another

15 were considered potential breeders (Appendix B)

Special Status Species Occurrence. Seventeen special status species (those with status

designations of special conservation concern from various state, regional, continental, and

global assessments) were detected at Jenner Headlands in 2010 and 2011 combined (Appendix

C). These were White-tailed Kite, Bald Eagle, Northern Harrier, Ferruginous Hawk, Golden

Eagle, Peregrine Falcon, Long-billed Curlew (fly over only), Burrowing Owl, Allen’s

Hummingbird, Nuttall’s Woodpecker, Purple Martin (aerial foraging only), Yellow Warbler,

Vesper Sparrow, Bryant’s Savannah Sparrow (the race of Savannah Sparrow that breeds along

the California coast from Humboldt Bay south to Morro Bay), Grasshopper Sparrow, and

Chestnut-collared Longspur (Appendices A and C). The Estero Americano supported three

special status species- Northern Harrier, Bryant’s Savannah Sparrow and Grasshopper Sparrow

(Appendices B and C).

Breeding was confirmed at both properties for Bryant’s Savannah Sparrow and Grasshopper

Sparrow (both are California bird species of special concern), and at the Jenner Headlands

breeding was suspected for Northern Harrier, Allen’s Hummingbird, and Oak Titmouse

(Appendix A). In 2011 a pair of Peregrine Falcons was observed with four dependent juveniles

on a rocky sea stack adjacent to the Jenner Headlands property (near the end of Munez Ranch

road), indicating that they likely nested somewhere in the immediate vicinity, though unknown

if they nested within the property boundary.

10

Vegetation. The grassland vegetation characteristics were very similar between the Jenner

Headlands and the Estero Americano (Figs. 7 and 8). The notable differences were that the

Estero Americano had an average of 7.4% forb cover, whereas the Jenner Headlands had nearly

three times that amount with 20.4% forb cover (Fig. 7). Also, the Estero Americano had trace

amounts of thatch accumulation, whereas no thatch was found at the Jenner Headlands. Both

properties has similar proportions of annual vs. perennial grasses, however the Estero

Americano had more native grasses with 9.1% of its grass cover comprised of natives,

compared with 3.8% at the Jenner Headlands (Fig. 8).

Mean grass height at the Jenner Headlands in 2011 was 54.8 cm, slightly less than the mean

height in 2010 of 57.2 cm, however the difference was not statistically significant (p>0.10).

Mean grass height at the Estero Americano in 2011 was 59.7, slightly greater than the Jenner

Headlands however the difference was not statistically significant (p>0.10). Grass height at the

Estero Americano point count stations varied from 43 to 88 cm, whereas at the Jenner

Headland point count stations, height varied from 23 to 112 cm in 2010 and 25 to 118 in 2011.

The grass heights measured at each releve subplot at the Jenner Headland in 2010 were highly

correlated with 2011 grass height measurements (Pearson correlation = 0.79), indicating that

location-specific grass height was relatively constant between the two years (Fig. 9).

Vegetation and Bird Abundance Correlations. All of the preselected variables we examined

(percent graminoid cover, H. lanatus cover, N. manicata cover, and grass height) were

positively associated with Grasshopper Sparrow abundance; however the polynomial

regression lines fitted through the scatter plots indicate the relationships are not linear (Fig.

10). The only variables that were significantly associated with Savannah Sparrow were percent

graminoid and H. lanatus cover, and these correlations were positive (Fig. 10). Additionally,

many of the vegetation variables were significantly correlated among themselves, such as the

relationship between graminoid cover and the two invasive grass species (Fig. 10).

11

Discussion

From the initial year of grassland bird monitoring at the Jenner Headlands in 2010, we found

that the two most abundant breeding species were Bryant’s Savannah Sparrow (Passerculus

sandwichensis alaudinus) and Grasshopper Sparrow (Ammodramus savannarum). Both species

are currently listed as California bird species of special concern, primarily because of historic

and ongoing habitat loss throughout their breeding range in California due to urban

development, conversion to row crops, and the succession of grassland habitat to scrub and

forest due to removal of livestock grazing and fire suppression (Shuford and Gardali 2008).

Based on our comparison of the Jenner Headlands grazed grasslands with the ungrazed Sonoma

Coast State Park in 2010, PRBO concluded that that grazing may be beneficial for certain

grassland birds in coastal grassland habitat of the region (DiGaudio 2010).

In contrast to the state park which has not been grazed in at least 20 years, the Estero

Americano Preserve was rested from grazing for 13 years between 1997 and 2010, and then

prescribed grazed for about four months in March – August of 2011 (S. Wright pers. com.). The

Estero Americano thus represents a less intensive grazing regime compared to the Jenner

Headlands, where grazing has been continuous for more than 120 years. Our comparison of

the grassland bird community in 2011 between the Jenner Headlands and the Estero Americano

revealed both similarities and subtle differences. For example, the Estero Americano had a

significantly higher relative abundance of Grasshopper Sparrow. Also, mean abundance of

Savannah Sparrow was slightly higher at the Jenner Headlands, though the difference was not

statistically significant. These results suggest that relatively light intermittent grazing may be as

effective as continual grazing for promoting grassland bird habitat, and possibly more effective

for certain species, such as the Grasshopper Sparrow. And while still benefiting grassland birds,

reducing grazing pressure could improve other habitat features in the landscape, such as

promoting regeneration of native plants and riparian corridors.

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The ~50% drop in Grasshopper Sparrow abundance at the Jenner Headland from 2010 to 2011

was somewhat of a surprise, especially since none of the other common bird species exhibited

sharp declines (Table 3, Fig. 5). When we looked at Grasshopper Sparrow abundance for each

of the three point count visits for both years, we found that abundance gradually increased

during the breeding season in 2010, indicating the birds were arriving and establishing

territories into June, whereas abundance during the 2011 breeding season remained stable

relative to the first visit (Fig. 6). This begs the question, was the 2011 Grasshopper Sparrow

decline the result of a real population decline or did the birds simply go elsewhere? The latter

is probably more likely, especially given that Grasshopper Sparrows are highly migratory and

are known for their low breeding site fidelity (Vickery 1996). If indeed the region’s Grasshopper

Sparrow population did not decline but rather redistributed itself elsewhere in its breeding

range, then this begs a second question: why? It does not seem likely that habitat conditions at

Jenner Headlands could explain the drop off in Grasshopper Sparrow numbers, since conditions

appeared to be very similar in both years and there were no major disturbances or changes in

management that occurred between 2010 and 2011. Indeed, other studies have indicated that

habitat quality is not necessarily a good predictor of Grasshopper Sparrow density (Vickery

1996). One hypothesis is that the above average rainfall and below average temperature of

late winter/spring of 2011 discouraged a number of birds from establishing territories at the

Jenner Headlands. Or alternatively, perhaps the climatic conditions of 2011 created suitable

Grasshopper Sparrow habitat elsewhere in the species’ breeding range, which would have

drawn birds away from the Jenner Headlands. In either scenario, we would need more

information about the species and its relationship with habitat and regional climate variables to

investigate these question further.

The fact that we did not find any grassland birds in the interior grasslands of the Jenner

Headlands property is probably indicative of the minimum patch size requirements of grassland

birds. In general, grassland birds are more likely to occupy large tracts of habitat rather than

small fragments (Vickery 1996). The interior grassland patches of the Jenner Headlands, which

range from 11.2 to 33.9 acres, may be too small to support grassland birds. In one study, the

13

minimum patch size requirements for Grasshopper Sparrows in Maine was 100 ha (247 acres),

whereas in Illinois it was about 30 ha (74 acres); though perhaps not directly comparable to

California grassland habitat, these reported minimum patch size requirements are much

greater than what the interior grasslands at Jenner Headlands can support (Vickery 1996).

Though we did not find grassland birds in the interior grasslands, we found that the grassland

area near the highest point in the property (~2,000 ft) supported an oak woodland bird

community not observed elsewhere on the property. The highest area search plot (JH-IG-4)

supported an arid, oak savannah annual grassland, which included a sparse stand of valley oaks

(Quercus lobata) and black oaks (Quercus kelloggii)- a distinct habitat type not observed

elsewhere on the property. Similarly, we observed bird species not seen elsewhere on the

property during the breeding season: Oak Titmouse, Lesser Goldfinch, and House Wren

(Appendix D).

We are still in the process of identifying the most important habitat variables for the grassland

birds. Our results from 2010 indicate that too much shrub cover has a negative impact, while

have some degree of bare ground in the interstitial spaces between grass clumps is an

important feature to maintain (DiGaudio 2010). Indeed, others that have demonstrated that

Grasshopper Sparrow and Savannah Sparrow require patches of bare ground, as this is where

they do most of their foraging (Whitmore 1981, Bock and Webb 1984, Shuford 1993, Vickery

1996, Fisher and Davis 2010). For this 2011 report, we investigated whether two invasive grass

species of potential management concern, Holcus lanatus (purple velvet grass) and Nassella

manicata (tropical needlegrass), affect grassland bird abundance. Correlation analysis indicates

a weak positive (though nonlinear) relationship between both grass species and Grasshopper

Sparrow abundance, and a weak correlation between H. lanatus and Savannah Sparrow

abundance (Fig. 10). However, it is difficult to say whether these two invasive grass species are

necessarily good or bad for grassland birds given that total graminoid cover is also correlated

with grassland bird abundance, and that graminoid cover is collinear with H. lanatus and N.

manicata cover (Fig. 10); correlation does not imply causation, and the collinearity among

14

independent variables makes it difficult to determine which variable has the causal effect (Zar

1999). Since the amount of grassland at the landscape scale is important (i.e. minimum patch

size requirements), then the amount of grass cover at the local scale should also be important.

But we have yet to determine the relative importance of specific grass species at the local scale,

something that may warrant further investigation if there is a concern for controlling certain

grass species or promoting others.

Future Research. We recommend that breeding season point counts continue in order to track

changes in the grassland bird population in the event that management practices (e.g. grazing

regime) of the property change. If annual grassland point count surveys are not feasible due to

fiscal constraints, then we recommend that they be conducted at some regular interval, e.g.

once every other year or once every three years. Although considerably more intensive, having

information on productivity and survivorship of the grassland birds would also help inform

resource management decision. For example, understanding the relationship between stocking

rates and nest success (especially with regard to nest failures caused by trampling) could help

inform stocking rates and grazing rotation schedules.

In addition to breeding season surveys, we recommend conducting fall and winter area search

surveys to assess the non-breeding season bird use of the Jenner Headlands grasslands. During

visits to the property during the fall months, we discovered through incidental observations

that there is a diverse and abundant group of grassland birds that use the Jenner Headlands

grasslands in the fall, including species that are not present during in the breeding season, such

as Burrowing Owl, a special status species. One potential standardized method for conducting

fall and winter bird surveys is the area search method, which could rely on volunteer citizen

scientists (Ralph et al. 1993).

Conclusions. The effects of various grazing, burning, and mowing regimes on grassland bird

communities have been shown to have complex and often contradictory results (Saab et al.

1995, Krausman et al. 2009). For example, light to moderate grazing has been shown to be

15

beneficial for Grasshopper Sparrows in productive grassland habitats of the tallgrass prairie and

eastern hayfields, whereas grazing is considered detrimental in arid grasslands, such as the

interior California grasslands and desert southwest (Saab et al. 1995). Our research on coastal

grasslands in Sonoma County suggest that livestock grazing may benefit certain grassland birds

in highly productive, mesic coastal prairies such as the Jenner Headlands and the Estero

Americano (Fitton 2008 and Unitt 2008). In addition to benefiting grassland birds, other studies

have shown that grazing may also be a useful management tool for promoting native plant

diversity in California coastal prairies, the most species rich grassland type in North America

(Stromberg et al. 2002, Hayes and Holl 2003). Determining the appropriate amount of grazing

in terms of intensity and timing remains a challenge, however, because these factors vary year

to year and region to region depending on climate, soil type, topography, and plant community

(Krausman et al. 2009). The level of grazing intensity at the Jenner Headlands is probably not

necessary to continue fostering grassland bird habitat given that the relatively low-intensity

seasonal grazing at the Estero Americano also appears to be sufficiently promoting grassland

bird habitat as well. Fire and mechanical vegetation removal appear to be the only alternatives

to livestock grazing as a disturbance management tool in California coastal prairies, and while

these practices can be useful under certain circumstances, they can also be costly and in the

case of fire, possibly risky. Grazing per se, however, is only one aspect of the management

equation for grassland habitat, and applying the optimal timing and intensity of grazing within

the context of an adaptive management framework is the key for achieving overall

management objectives.

16

Acknowledgements

This project would not have been possible without funding and support from the Sonoma Land

Trust (SLT). We especially thank Brook Edwards, SLT project manager for the Jenner Headlands,

for affording PRBO the opportunity to initiate this project, and Shanti Wright, SLT project

manager for the Estero Americano Preserve, for her enthusiastic support of our work at the

Estero Americano. We also thank Lisa Bush for her insightful review of the 2010 report and for

providing lots of thought provoking questions; Brendan O’Neil, senior environmental scientist

for California State Parks, for granting us permission to work on Sonoma Coast State Park lands

in 2010 and for his feedback on the 2010 report; Geoffrey Geupel and Renée Cormier for their

initial involvement in the project in setting up the study design; Peter Gilbert for his assistance

in conducting point count surveys in 2010; Khara Strum for her assistance in collecting

vegetation and RDM data, and for assisting with point count surveys in 2011; Aaron Holmes for

providing technical assistance on designing the vegetation assessment protocol; and both Peter

Connors and Peter Warner for helping with plant identification.

17

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W.W. Piegorsch (ed.). Encyclopedia of Environmetrics. John Wiley and Sons, Ltd,

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Gardali (eds). California Bird Species of Special Concern: a ranked assessment of species,

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California. Studies of Western Birds 1. Western Field Ornithologists, Camarillo,

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Vickery, P.D. 1996. Grasshopper Sparrow (Ammodramus savannarum). In The Birds of North

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Zar, J.H. 1999. Biostatistical Analysis, Fourth Edition. Prentic Hall. Upper Saddle River, New

Jersey.

21

Figure 1. Location of the Jenner Headlands property, showing the 66 point count stations in the western grassland area and the six area search

plots (labeled) in interior grassland patches.

22

Figure 2. Locations of the 66 point count stations (with station names) in grassland habitat at

Jenner Headlands overlaid on vegetation type.

Figure 3. Locations of the 9 point count stations in grassland habitat at the Estero Americano

Preserve ~12 miles SSE of the Jenner Headlands.

23

Figure 4. Box plots depicting the abundance of Grasshopper, Savannah, Song, and White-

crowned sparrows at the Jenner Headlands and the Estero Americano in 2011, where

abundance = total number of individuals detected within 100 m of each point count station (n=

66 both years). Grasshopper Sparrows were significantly more abundant at the Estero

Americano (Monte-Carlo permutation test p<0.05). The shaded box indicates the central 50% of

the data (also called the the inter-quartile range, or IQR), the horizontal line within the box

indicates the median, the whiskers indicate data values that fall within 1.5 * IQR beyond the

box limits, and the hollow circles represent outliers.

Estero Americano Jenner Headlands

02

46

8

Grasshopper SparrowIn

div

iduals

per

poin

t

Estero Americano Jenner Headlands

02

46

810

Savannah Sparrow

Indiv

iduals

per

poin

t

Estero Americano Jenner Headlands

01

23

45

67

Song Sparrow

Indiv

iduals

per

poin

t

Estero Americano Jenner Headlands

02

46

8

White-crowned SparrowIn

div

iduals

per

poin

t

24

Figure 5. Box plots depicting the 2010 and 2011 abundance of Grasshopper, Savannah, Song,

and White-crowned sparrows at the Jenner Headlands in 2010 and 2011, where abundance =

total number of individuals detected within 100 m of each point count station (n= 66 both

years). The shaded box indicates the central 50% of the data (also called the the inter-quartile

range, or IQR), the horizontal line within the box indicates the median, the whiskers indicate

data values that fall within 1.5 * IQR beyond the box limits, and the hollow circles represent

outliers. There were significantly fewer Grasshopper Sparrows in 2011 than in 2010 (Monte-

Carlo permutation test p=0.01)

2010 2011

01

23

45

67

Grasshopper Sparrow

Indiv

iduals

per

poin

t

2010 2011

02

46

810

Savannah Sparrow

Indiv

iduals

per

poin

t

2010 2011

02

46

8

Song Sparrow

Indiv

iduals

per

poin

t

2010 2011

02

46

810

White-crowned Sparrow

Indiv

iduals

per

poin

t

25

Figure 6. Average Grasshopper Sparrow abundance for each visit at the Jenner Headlands in

2010 and 2011, where visit 1 = mid May, 2=late May, and 3=mid June. Abundance gradually

increased in 2010 but remained stable throughout the 2011 breeding season.

Figure 7. Average percent cover (with standard error bars) of graminoids, forbs, shrubs,

trees, bare ground, thatch, and rocks around point count stations in Jenner Headlands and

the Estero Americano Preserve grasslands.

0.00

0.10

0.20

0.30

0.40

0.50

0.60

0.70

1 2 3

av

era

ge

in

div

idu

als

pe

r p

oin

t

Visit

Grasshopper Sparrow abundance at Jenner Headlands

2010 2011

0

10

20

30

40

50

60

70

80

graminoids forbs shrubs trees bare thatch rocks

Pe

rce

nt

cov

er

Jenner Headlands Estero Americano

26

Figure 8. Average composition of grass species by duration (annual vs. perennial) and by

native status (with standard error bars) at the Jenner Headlands and the Estero Americano

Preserve.

Figure 9. The relationship between 2010 and 2011 average grass height at each Jenner

Headland point count station. The close correlation indicates that grass height, an indicator of

grazing intensity, was very similar between years.

0

10

20

30

40

50

60

70

80

90

100

annual perennial introduced native

pe

rce

nt

of

gra

ss c

ov

er

Jenner Headlands Estero Americano

20 40 60 80 100 120

20

40

60

80

10

012

0

Grass Height 2010 vs 2011

2011 Grass Height (cm)

201

0 G

rass H

eig

ht (c

m)

Pearson correlation = 0.79

27

Figure 10. Correlation matrix depicting the relationship between Grasshopper Sparrow (GRSP) and

Savannah Sparrow (SAVS) abundance and grass height, grass cover, Holcus lanatus cover, and

Nassella manicata cover. Numbers represent Spearman correlation coefficients, and red asterisks

indicate significance levels (p-values), were * p< 0.01, ** p<0.001, and ***p<0.0001. The red line in

the scatter plot is a locally-weighted polynomial regression.

GRSP

0 2 4 6 8 10

0.39** 0.31 *

0.2 0.4 0.6 0.8

0.29 * 0.43***

0.00 0.10 0.20 0.30

01

23

45

6

0.45***

02

46

810

SAVS 0.037

0.33** 0.41*** 0.026

Grass_ht 0.061

0.55***

40

80

120

0.60***

0.2

0.4

0.6

0.8

Grass_cov 0.34** 0.35**

H_lanatus

0.0

0.2

0.4

0.6

0.40***

0 1 2 3 4 5 6

0.0

00.1

50.3

0

40 60 80 100 0.0 0.2 0.4 0.6

N_manicata

28

Table 1. Date ranges over which each of the three survey visits took place in 2010 and 2011 at the

Jenner Headlands. Note that 2010 dates include the Sonoma Coast State Park surveys, and 2011

dates include the Estero Americano Preserve surveys.

Point Count

Visit # 2010 2011

1 May 10 - May 13 May 10 - May 13

2 May 28 - May 31 May 28 - June 3

3 June 8 - June 12 June 13 - June 16

Table 2. Jenner Headland interior grassland area search plot acreage and schedule of 2011 survey

dates.

Visit

Area Search Plot (with area in acres)

JH-IG-1

(33.9 ac)

JH-IG-2

(12.6 ac.)

JH-IG-3

(14.3 ac.)

JH-IG-4

(20.2 ac.)

JH-IG-5

(15.7 ac.)

JH-IG-6

(11.2 ac.)

1 12-May 29-May 29-May 29-May 29-May 30-May

2 29-May 15-June 15-June 15-June -- --

3 15-June 1-July 1-July 1-July -- --

4 1-July -- -- -- -- --

29

Table 3. Abundance indices for 15 of the most abundant species detected during breeding season

point count surveys at Jenner Headlands in 2010 and 2011 (ranked by 2010 abundance) and the 19

most abundance species at the Estero Americano in 2011 (listed 19 because 4 species tied for the 15th

ranking). The abundance index represents the total number of individuals detected within 100 m of

each point count station for all visits combined, averaged over all stations for each site (standard

error given in parenthesis).

2010 2011

Jenner Headlands

Savannah Sparrow 2.53 (±0.39) 2.12 (±0.37)

Grasshopper Sparrow 1.53 (±0.22) 0.82 (±0.15)

Song Sparrow 1.52 (±0.25) 1.73 (±0.26)

White-crowned Sparrow 0.94 (±0.21) 1.50 (±0.3)

California Towhee 0.91 (±0.17) 1.03 (±0.16)

American Goldfinch 0.56 (±0.16) 0.50 (±0.13)

European Starling 0.53 (±0.2) 0.21 (±0.08)

Spotted Towhee 0.52 (±0.13) 0.30 (±0.08)

Western Scrub-jay 0.48 (±0.16) 0.59 (±0.12)

Wrentit 0.48 (±0.15) 0.39 (±0.11)

Bushtit 0.47 (±0.19) 0.15 (±0.08)

Wilson's Warbler 0.45 (±0.12) 0.38 (±0.09)

Western Bluebird 0.42 (±0.12) 0.45 (±0.11)

Chestnut-backed Chickadee 0.39 (±0.16) 0.15 (±0.07)

Bewick's Wren 0.36 (±0.09) 0.32 (±0.08)

Estero Americano

Grasshopper Sparrow -- 2.00 (±1.03)

Song Sparrow -- 1.33 (±0.41)

European Starling -- 1.00 (±0.71)

Savannah Sparrow -- 0.78 (±0.55)

White-crowned Sparrow -- 0.78 (±0.32)

American Goldfinch -- 0.56 (±0.24)

Spotted Towhee -- 0.56 (±0.44)

Bewick's Wren -- 0.44 (±0.24)

Brown-headed Cowbird -- 0.33 (±0.24)

Black Phoebe -- 0.33 (±0.17)

Turkey Vulture -- 0.33 (±0.33)

Western Bluebird -- 0.33 (±0.24)

Western Scrub-jay -- 0.33 (±0.24)

Wrentit -- 0.33 (±0.33)

Anna's Hummingbird -- 0.22 (±0.15)

Brewer's Blackbird -- 0.22 (±0.15)

Calfiornia Towhee -- 0.22 (±0.22)

Common Raven -- 0.22 (±0.22)

Lazuli Bunting -- 0.22 (±0.15)

30

Table 4. Density and population estimates for Grasshopper Sparrow and Savannah Sparrow at

the Jenner Headlands, generated with the program DISTANCE using point count survey data

from 2010 and 2011 (same 66 points surveyed both years). %CV = coefficient of variation

(standard error/estimated density), Do = detection probability, D1 = estimated density

(birds/acre), and estimated number of birds on the 1189.9 acre Jenner Headlands coastal

grassland.

Species Year %CV Do D1 (95% C.I.) Estimated number of

birds (95% C.I.)

Grasshopper Sparrow 2010 13.69 94.7 0.10 (0.07-0.13) 116 (88-151)

2011 15.55 96.0 0.04 (0.03-0.06) 53 (39-72)

Savannah Sparrow 2010 19.76 91.0 0.39 (0.27-0.58) 467 (317-687)

2011 21.23 90.4 0.34 (0.23-0.52) 408 (269-617)

31

Appendix A. All species (114 total) found in 2010 and 2011 at Jenner Headland, including incidental

observations. Breeding status codes: B = confirmed; b = likely; and (b) = potential. Migration status

codes: M = migratory; (M) migratory and (R) and only present during the fall / winter; and R = year

round resident. Species listed in taxonomic order.

Common Name Scientific Name Breeding

Status

Migration

Status

Cackling Goose Branta hutchinsii (M)

Common Merganser Mergus merganser

M

Mountain Quail Oreortyx pictus (b) R

California Quail Callipepla californica b R

Wild Turkey Meleagris gallopavo B R

Great Blue Heron Ardea herodias R

Turkey Vulture Cathartes aura b R

Osprey Pandion haliaetus b M

White-tailed Kite Elanus leucurus (b) R

Bald Eagle Haliaeetus leucocephalus (b) R

Northern Harrier Circus cyaneus (b) R

Sharp-shinned Hawk Accipiter striatus (M)

Cooper's Hawk Accipiter cooperii (b) M

Red-shouldered Hawk Buteo lineatus R

Red-tailed Hawk Buteo jamaicensis B R

Ferruginous Hawk Buteo regalis (M)

Golden Eagle Aquila chrysaetos R

American Kestrel Falco sparverius (b) R

Peregrine Falcon Falco peregrinus (b) M

Killdeer Charadrius vociferus R

Long-billed Curlew Numenius americanus M

Wilson's Snipe Gallinago delicata (M)

Band-tailed Pigeon Patagioenas fasciata b R

Mourning Dove Zenaida macroura b R

Great Horned Owl Bubo virginianus B R

Burrowing Owl Athene cunicularia (M)

Vaux's Swift Chaetura vauxi M

Anna's Hummingbird Calypte anna b R

Rufous Hummingbird Selasphorus rufus M

Allen's Hummingbird Selasphorus sasin b M

Acorn Woodpecker Melanerpes formicivorus b R

Nuttall's Woodpecker Picoides nuttallii (b) R

Downy Woodpecker Picoides pubescens (b) R

Hairy Woodpecker Picoides villosus b R

Northern Flicker Colaptes auratus (b) R

Pileated Woodpecker Dryocopus pileatus b R

32

Common Name Scientific Name Breeding

Status

Migration

Status

Olive-sided Flycatcher Contopus cooperi b M

Western Wood-Pewee Contopus sordidulus b M

Pacific-slope Flycatcher Empidonax difficilis b M

Black Phoebe Sayornis nigricans b R

Say's Phoebe Sayornis saya (M)

Ash-throated Flycatcher Myiarchus cinerascens b M

Western Kingbird Tyrannus verticalis (b) M

Cassin's Vireo Vireo cassinii (b) M

Hutton's Vireo Vireo huttoni b R

Warbling Vireo Vireo gilvus b M

Steller's Jay Cyanocitta stelleri b R

Western Scrub-Jay Aphelocoma californica B R

American Crow Corvus brachyrhynchos (b) R

Common Raven Corvus corax B R

Horned Lark (California) Eremophila alpestris b R

Purple Martin Progne subis b M

Violet-green Swallow Tachycineta thalassina B M

Northern Rough-winged Swallow Stelgidopteryx serripennis (b) M

Cliff Swallow Petrochelidon pyrrhonota b M

Barn Swallow Hirundo rustica b M

Chestnut-backed Chickadee Poecile rufescens b R

Oak Titmouse Baeolophus inornatus (b) R

Bushtit Psaltriparus minimus b R

Red-breasted Nuthatch Sitta canadensis (b) R

White-breasted Nuthatch Sitta carolinensis (b) R

Pygmy Nuthatch Sitta pygmaea b R

Brown Creeper Certhia americana b R

Rock Wren Salpinctes obsoletus B M

Bewick's Wren Thryomanes bewickii b R

House Wren Troglodytes aedon (b) M

Pacific Wren Troglodytes pacificus (b) R

Golden-crowned Kinglet Regulus satrapa b R

Ruby-crowned Kinglet Regulus calendula (M)

Western Bluebird Sialia mexicana B R

Swainson's Thrush Catharus ustulatus b M

Hermit Thrush Catharus guttatus b M

American Robin Turdus migratorius b R

Varied Thrush Ixoreus naevius (M)

Wrentit Chamaea fasciata b R

European Starling Sturnus vulgaris B R

American Pipit Anthus rubescens (M)

33

Common Name Scientific Name Breeding

Status

Migration

Status

Cedar Waxwing Bombycilla cedrorum M

Orange-crowned Warbler Oreothlypis celata b M

Yellow Warbler Setophaga petechia (M)

Yellow-rumped Warbler Setophaga coronata b M

Townsend's Warbler Setophaga townsendi (M)

Hermit Warbler Setophaga occidentalis b M

Palm Warbler (Western) Setophaga palmarum (M)

Wilson's Warbler Cardellina pusilla b M

Spotted Towhee Pipilo maculatus b R

California Towhee Melozone crissalis b R

Rufous-crowned Sparrow Aimophila ruficeps b R

Chipping Sparrow Spizella passerina b M

Clay-colored Sparrow Spizella pallida (M)

Vesper Sparrow Pooecetes gramineus (M)

Lark Sparrow Chondestes grammacus B R

Savannah Sparrow (Bryant's) Passerculus sandwichensis

alaudinus

B R

Grasshopper Sparrow Ammodramus savannarum

perpallidus

B M

Song Sparrow Melospiza melodia B R

Lincoln's Sparrow Melospiza lincolnii (M)

White-crowned Sparrow Zonotrichia leucophrys B R

Golden-crowned Sparrow Zonotrichia atricapilla (M)

Dark-eyed Junco (Oregon) Junco hyemalis b R

Lapland Longspur Calcarius lapponicus (M)

Chestnut-collared Longspur Calcarius ornatus (M)

Western Tanager Piranga ludoviciana b M

Black-headed Grosbeak Pheucticus melanocephalus b M

Lazuli Bunting Passerina amoena b M

Red-winged Blackbird Agelaius phoeniceus (M)

Western Meadowlark Sturnella neglecta M

Brewer's Blackbird Euphagus cyanocephalus (b) R

Brown-headed Cowbird Molothrus ater b M

Bullock's Oriole Icterus bullockii b M

Purple Finch Carpodacus purpureus b R

House Finch Carpodacus mexicanus B R

Pine Siskin Spinus pinus b R

Lesser Goldfinch Spinus psaltria (b) R

American Goldfinch Spinus tristis b R

34

Appendix B. All species (44 total) detected in 2011 at the Estero Americano Preserve, including

incidental observations. Breeding status codes: B = confirmed; b = likely; and (b) = potential. Migration

status codes: M = migratory.

Common Name Scientific Name Breeding

Status

Migratory

Status

Canada Goose Branta canadensis (b) M

Gadwall Anas strepera (b) M

California Quail Callipepla californica b R

Wild Turkey Meleagris gallopavo (b) R

Great Blue Heron Ardea herodias R

Great Egret Ardea alba M

Turkey Vulture Cathartes aura R

Northern Harrier Circus cyaneus (b) R

Red-tailed Hawk Buteo jamaicensis (b) R

Semipalmated Plover Charadrius semipalmatus M

Eurasian Collared-Dove Streptopelia decaocto (b) R

Mourning Dove Zenaida macroura b R

Great Horned Owl Bubo virginianus (b) R

Anna's Hummingbird Calypte anna b R

Black Phoebe Sayornis nigricans b R

Hutton's Vireo Vireo huttoni (b) R

Western Scrub-Jay Aphelocoma californica B R

Common Raven Corvus corax (b) R

Cliff Swallow Petrochelidon pyrrhonota M

Barn Swallow Hirundo rustica (b) M

Chestnut-backed Chickadee Poecile rufescens (b) R

Bushtit Psaltriparus minimus (b) R

Pygmy Nuthatch Sitta pygmaea (b) R

Bewick's Wren Thryomanes bewickii b R

Western Bluebird Sialia mexicana b R

Swainson's Thrush Catharus ustulatus b M

American Robin Turdus migratorius (b) R

Wrentit Chamaea fasciata b R

European Starling Sturnus vulgaris b R

Orange-crowned Warbler Oreothlypis celata b M

Wilson's Warbler Cardellina pusilla b M

Spotted Towhee Pipilo maculatus b R

California Towhee Melozone crissalis b R

Savannah Sparrow (Bryant's) Passerculus sandwichensis

alaudinus

B R

Grasshopper Sparrow Ammodramus savannarum

perpallidus

B M

35

Common Name Scientific Name Breeding

Status

Migratory

Status

Song Sparrow Melospiza melodia b R

White-crowned Sparrow Zonotrichia leucophrys b R

Lazuli Bunting Passerina amoena b M

Red-winged Blackbird Agelaius phoeniceus b M

Western Meadowlark Sturnella neglecta M

Brewer's Blackbird Euphagus cyanocephalus (b) R

Brown-headed Cowbird Molothrus ater b M

House Finch Carpodacus mexicanus b R

Pine Siskin Spinus pinus (b) R

American Goldfinch Spinus tristis b R

36

Appendix C. Species detected on Jenner Headlands property in 2010 and 2011 with status

designations of special conservation concern from state, regional, continental, and global

assessments.

Common Name BSSCa T&E

b USFWS 2008

c

Fully

Protectedd

White-tailed Kite x

Bald Eagle SE R, 32 x

Northern Harrier 3

Ferruginous Hawk [R]

Golden Eagle x

Peregrine Falcon SE R, 32 x

Long-billed Curlew R, 32

Burrowing Owl 2 R, 32

Allen's Hummingbird R, 32

Nuttall's Woodpecker 32

Purple Martin 2

Oak Titmouse 32

Yellow Warbler 2 32

Vesper Sparrow 2

Bryant's Savannah Sparrow 3

Grasshopper Sparrow 2

Chestnut-collared Longspur [R]

aSpecies, subspecies, and distinct populations on the 2006 list of California Bird Species of Special

Concern (Shuford and Gardali 2008) that occur in the Central Valley. Numbered designations indicate

priority levels within the list (1, 2, or 3; highest to lowest). bSpecies listed as threatened or endangered by state or federal law. ST, state threatened; SE, state

endangered; FT, federally threatened; FE, federally endangered. cSpecies or subspecies on the USFWS list of Birds of Conservation Concern 2008 (USFWS 2008);

includes taxa of lesser concern than those listed as Federally threatened or endangered (see footnote babove). R refers to USFWS Region 8 (CA and NV); the number 32 refers to Bird Conservation Region

32 (Northern California); and [R] refers to USFWS regions other than for Region 8. dSpecies listed by California state law as “fully protected”

(www.dfg.ca.gov/wildlife/species/t_t_spp/fully_pro.html).

37

Appendix D. Summary of interior grassland area searches, with species and total number of individuals

detected from all visits. All birds were detected from the forested edge of the grassland plots.

Common Name Area Search Plot

JH-IG-1 JH-IG-2 JH-IG-3 JH-IG-4 JH-IG-5 JH-IG-6

Mountain Quail

1 1 1

California Quail

1

4

Wild Turkey

5

Red-tailed Hawk 2

American Kestrel

1

Acorn Woodpecker

3 2

Downy Woodpecker 1

Pileated Woodpecker

1

Pacific-slope Flycatcher 2 1

Cassin's Vireo

1

Hutton's Vireo 1 1

1

1

Warbling Vireo 2

1

Steller's Jay 3 4 1 1 1 1

Western Scrub-Jay

1 1

Common Raven 2

1

Violet-green Swallow 1

2

Cliff Swallow

12 1

Chestnut-backed

Chickadee 6

2 1 1

Oak Titmouse

1

White-breasted Nuthatch

2 3

Brown Creeper 1

Bewick's Wren

1

House Wren

1

Western Bluebird

1

2

Hermit Thrush 3

American Robin 2 1 1 1

Orange-crowned Warbler

2

Wilson's Warbler 1

1

Spotted Towhee

1

California Towhee

2

3

Rufous-crowned Sparrow

1

Chipping Sparrow

1

Oregon Junco 8 3

2

Western Tanager

1 2

Lazuli Bunting

1 2

Purple Finch

1

Lesser Goldfinch

3