Cover:A Terek Sandpiper patrols the rocky shore ofAttu Island,Alaska, in late May 1999. See the Birding Perspectve (page

. 488) and the Attu Showcase (page 545) for more. The equipment for this photograph by Jim Burns wos a Canon A2 camera body, a

L- . ' Canon 300mm f12.8 lens with a Canon 2x teleconverter, and Fuji Velvia film.

A M E R I C A N B I R D I N G A S S O C I A T I O N VOLUME 32: NUMBER 6 DECEMBER 2 0 0 0 u

A Birding Perspective Attu Reflections Your Letters

The Next New ABA-Area Birds Western Alaska by Thede G . Tobish Birding Essay The Flying Red Kiss by Will Nixon Possible Anywhere Shiny Cowbird by Bill Pranty Answers to the August Photo Quiz by Kimball Garrett PointlCounterpoint Buff-breasted or Hybrid by Mark B. Robbins and Jonathan K. Alderfer On Second-Alternate White-winged Terns by Paul Doherty and Colin Campbell An Attu Showcase

Tools of the Trade High-end Roofs by Stephen Ingraham Book and Media Reviews The Sibley Guide to Birds Birds of the World Grasslands Raptors of Europe New Zealand Rails Herons Birds of Paradise Breeding Systems The Joy of Birding Luck of the Draw by Brenda Carter New Photo Quiz

Advertisers List page 59 1

possible anywhere

Shiny Cowbird

Bill Pranty*

RY, three bird species invaded the ABA Area by way of Florida. First was the Cattle Egret (Bubulcus ibis) in the 1940s, fol- lowed four decades later by the exotic Eurasian Collared-Dove (Streptopelia decaocto) and the Shiny Cowbird (Molothrus bonariensis; Figure 1). From dif- ferent points of origin, all three species moved through or from the West Indies to reach Florida, then spread northward and west- ward across many other states and into Canada. Deforestation of Caribbean islands for agricul- ture and animal husbandry allowed Shiny Cowbirds to spread throughout the West Indies in the past 100 years (Post and Wiley 1977, Post et al. 1993, Lowther and Post 1999). First discovered in the ABA Area in Florida in 1985, Shiny Cowbirds have been observed as far north as New Brunswick and Maine, and as far west as Oklahoma and Texas. Despite these distant wanderings, the Shiny Cowbird is presently a rare bird in the ABA Area except in

*Audubon of Florida 4 10 Ware Boulevard. Suite 702 Tampa, Florida 336 19 billpranty@hotmail.com BP is coordinating the Florida Important Bird Areas Program and a Florida Scrub-Jay habitat restoration project for the state office of the National Audubon Society. He is the author of A Birder's Guide to Florida (ABA 1996), and a

number of scientific papers, and is the Florida Region spring and fall seasonal editor for North American Birds.

K W I L L I A W SWl 1 H l V l K t U

Figure I . This photograph, taken at Flamingo, Everglades National Park, Florida, on 25 May 1987, shows a male and a female Shiny Cowbird (in back) with a male Brown-headed Cowbird (in front). Note the more slender body, flatter head, and longer tail of the Shiny Cowbird, as well as the subtly diferent bill shape. In the hand, Shiny Cowbirds have a shorter primary extension than Brown-headed Cowbirds, but this difference may be dif7icult to discern in the field.The series of photographs that includes Figure I is believed to be the first docu- mentation of Shiny and Brown-headed Cowbirds occurring together anywhere.

southern Florida. Most occur- rences have been at coastal sites during spring, when small to occasionally sizable flocks of cowbirds disperse to the conti- nent, presumably from Cuba.

Five of the seven subspecies of the Shiny Cowbird are restricted to South America, while a sixth, M.6. cabanisii, occurs in Panama and Colombia. The seventh, M.6. minimus, has advanced across the Caribbean from its original range in Trinidad, Tobago, and a small adjacent part of the South American mainland (Blake 1968, Lowther and Post 1999). Other subspecies have colonized deforested areas elsewhere in South America (Ridgely and Tudor 1989), and one of them (M. b. bonariensis)

now is widespread in parts of Chile from accidental or inten- tional releases (Blake 1968, Lowther and Post 1999).

Shiny Cowbirds commonly roost with blackbirds, grackles, and other cowbirds. At sites where other icterids are absent (e.g., Dry Tortugas National Park, Florida), they are found singly or in flocks apart from other species. Shiny Cowbirds feed mostly on insects and spi- ders, and seem especially fond of caterpillars. About 10 percent of their diet consists of grains obtained from the ground or at animal feed troughs and bird feeders (Lowther and Post 1999). They also glean arthropods from the ground, shrubs, and trees, and birds in the West Indies have

BIRDING. DECEMBER 2000

Figure 2.Adult male Shiny Cowbirds are the only truly all-black iaerids occurring in the ABA Area, with black plumage and blackish sofl parts. The body shows bluish or purplish iridescence throughout. Compared to Brown- headed and Bronzed Cowbirds, note the more slender body, flat head, pointed bill, and longish tail.The black, glossy head easily distinguishes males from male Brown-head- ed Cowbirds, and the dark irides rule out males of Bronzed Cowbirds and Brewer's Blackbirds. This Shiny Cowbird was pho- tographed in April 1997 at Dry Tortugas National Park, Florida, one of the most reli- able spots in the ABA Area to see this species.

been observed flyca tching (Lowther and Post 1999).

Cowbird taxonomy has recently been revised. Previously, taxonomists had included five species in the genus Molothrus. In addition to the Shiny, these were the Brown-headed (M. ater) and Bronzed (M. aeneus) Cowbirds of North and Middle America, and the Bay-winged (M. badius) and Screaming (M. rufoaxillaris) Cowbirds of South America. Four of these species are obligate brood parasites; M. badius is the exception. Based on mitochondria1 DNA analysis, Johnson and Lanyon (1999) pro- posed a revision of some of the New-World blackbirds, including the genus Molothrw. They pro- posed moving the Bay-winged Cowbird from Molothrtrs to Oreopsar. The remaining Molothrus species are closely related to the brood-parasitic Giant Cowbird (Scdphidura oryzivora) of Middle and South America, which they proposed for merger into Molothrus. The AOU (2000) has agreed with this revised taxonomy, resulting in a reconfigured Molothrus genus that consists exclusively of the five obligate brood-parasitic cow-

SHINY COWBIRD

bird species. Since its arrival in the ABA

Area, the Shiny Cowbird's advance has been a subject of concern because of its potential effect on breeding passerines, most of which are already under reproductive stress from Brown- headed or Bronzed Cowbirds. Female Shiny Cowbirds lay their eggs in the nests of other birds, usually passerines larger than themselves (Lowther and Post 1999). Throughout their wide range, Shiny Cowbirds are docu- mented as parasitizing 232 species, but only 74 of these have successfully reared cowbird young (Lowther and Post 1999). Cruz et al. (1998) consider the following species to be moderate- ly or highly vulnerable to Shiny Cowbird brood parasitism in Florida: White-eyed Vireo (Vireo griseus), Red-eyed Vireo (V oli- vaceus), Black-whiskered Vireo (V altiloqtlus), Yellow Warbler (Dendroica petecbia), Prairie Warbler (D. discolor), Common Yellowthroat (Geotblypis trichas), Northern Cardinal (Cardinalis cardinalis), Eastern Towhee (Pipilo evythrophthalmus), and Red- winged Blackbird (Agelaius

LARRY SANSONE

phoeniceus). However, Prather and Cruz (1995) found no evi- dence of cowbird parasitism in nests of Yellow Warbler (n = 20) and Prairie Warbler (n = 42) monitored on and near Key Largo, Florida, from 1990 to 1993.

The eggs of M.b. minimus average 20.6 by 16.4 mm and occur in two color morphs. Spotted or blotched eggs are white, pale yellow, pale gray, or pale blue, and are marked with black, brown, or reddish patterns (Baicich and Harrison 1997, Lowther and Post 1999). Some of these eggs closely resemble those of Brown-headed Cowbirds, but Shiny Cowbirds also lay unmarked eggs that usu- ally are white, but may be very pale blue; these bear no resem- blance to Brown-headed Cowbird eggs (Baicich and Harrison 1997). Eggs hatch after 10 to 13 days, and the young fledge after another 12 to 15 days (Lowther and Post 1999). In Puerto Rico, egg-laying has occurred from 10 March to 28 October, with a peak in June and July (Lowther and Post 1999).

Through 1999, there is no published evidence that Shiny

515

possible anywhere

Cowbirds have definitely para- sitized a nest in the ABA Area, but observations suggest that breeding has occurred in Florida and elsewhere. Among several anecdotes in Florida, Larry Manfredi (pers. comm.) watched a female Shiny Cowbird near Kendall in April 1998 fly to an unattended Red-winged Blackbird nest and remain on it for three to four minutes-suffi- cient time to lay an egg (Lowther and Post 1999). Unfortunately, the nest could not be checked for two weeks, at which time it con- tained only a nestling blackbird. Elsewhere in Florida, juvenile Shiny Cowbirds have twice been identified in areas where adults were present: a t Flamingo in Everglades National Park in June-July 1987 (Smith and Sprunt 1987), and a t Bald Point, in the Florida Panhandle, on 6 September 1995 (J. Dozier in Pranty 1995). One of the cow- birds collected by Post (1992) near Fort Pierce on 25 July 1991 was an adult male with enlarged testes, which may suggest local breeding.

In 1991, during the Florida Breeding Bird Atlas project (Kale et al. 1992), a young Shiny Cowbird was reportedly observed being fed by a Red-winged Blackbird a t Homestead. This report has been cited frequently (e.g., Robertson and Woolfenden 1992, Stevenson and Anderson 1994, Lowther and Post 1999), but a review of the original FBBA data card reveals an apparent inconsistency. The cowbird was called "v[ery] young" but was identified as a Shiny because it was "just starting song." The age at which song development begins in Shiny and Bronzed Cowbirds is unknown (Lowther 1995, Lowther and Post 1999),

BRIAN E. SMALL

Figure 3. The identification of male Brown-headed Cowbirds is straightforward. Most conspicu- ous, of course, is the brown head that contrasts with the black body.The iridescence is green or greenish-blue. Brown-headed Cowbirds are stockier than Shiny Cowbirds, with shorter toils, rounded heads, and the most conical bills of the three cowbird species found in the ABA Area. This mole was photographed at South Padre Island, Texos, in May 1998.

BRIAN E. SMALL

Figure 4. Mole Bronzed Cowbirds hove block bodies with bronzy iridescence on the body and bluish iridescence on the wings and toil. Distinctive in both moles and femoles ore the conspic- uous red irides. Moles have o ruff of feathers on the nope that can give them a hunch-backed appearance. Note olso the substantial bill of this individual. Two subspecies of the Bronzed Cowbird occur in the ABA Areo. M.a. aeneus is primarily a summer resident in southern and eastern Texos with on isolated breeding population around New Orleans, Louisiana; some indi- viduals hove begun wintering regularly in Florida in recent yeors. M.a. loyei breeds from extreme southeostern California east to western Texas, and olso is much less common in the ABA Areo during the winter months. In recent yeors, the breeding ranges of M.a. aeneus and M.a. loyei hove come into contact in western Texos. Moles of these two subspecies ore very similar, but femoles can be distinguished by plumage characteristics. This mole of the aeneus subspecies was photographed at Bentsen State Pork,Texos, in December 1999.

BIRDING, DECEMBER 2000

but in Brown-headed Cowbirds it begins when the birds are five to seven months old (Lowther 1993). In light of this possible inconsistency, and further consid- ering that the identification was not supported with details, it seems wise to disregard the report.

Identification Shiny Cowbirds are small black- birds that can be confused with only a few other icterids in the ABA Area. M.b. minimus is the smallest subspecies of the Shiny Cowbird, with a total length of about 18 cm. (Figures 1 and 2). Although the Brown-headed Cowbird is the predominant cowbird species occurring within the current range of the Shiny Cowbird in the ABA Area, this section also discusses field identi- fication criteria for Bronzed Cowbirds and Brewer's Blackbirds.

Shiny Cowbirds have a sleeker and more elegant profile than Brown-headed (Figures 1 and 3) and Bronzed (Figure 4) Cowbirds due to a slimmer body, flatter head, longer tail, and-thinner bill (Smith and Sprunt 1987, Jaramillo and Burke 1999). All soft parts, including the eyes, are

KEVIN T KARLSON

Figure 6. This first-year male Shiny Cowbird was photographed at the Dry Tortugas, Florida, in May 1993, Immature males are similar to adults, but they retain some brown feathering from juvenal plumage into their second calendar year. Note the brown in the primaries, secondaries, and median coverts, and scattered brown feathering on the flanks and lower belly. By their second spring (i.e., in their third calendar year) males have '-. . .::--... attained adult plumage. The slender body shape and proportionately longer tail of Shiny *.

Cowbirds are evident here.

dark. The bill is proportionately thinner and more pointed than those of Brown-headed or Bronzed Cowbirds (Figure 5) . Adult Shiny and Bronzed Cowbirds have entirely dark bills; the lower mandibles of some Brown-headed Cowbirds have pale bases (Jaramillo and Burke 1999). The Shiny Cowbird's wingtips do not extend to the base of the tail, whereas they do in Brown-head-

* * . .,

ed and Bronzed Cowbirds (Pyle --

1997). However, this character may not be usable in the field (Jaramillo and Burke 1999). Male Shiny Cowbirds are easily identified when seen well. On the other hand, the identification of females and juveniles requires great care (Jaramillo and Burke 1999).

Males can be distinguished from Brown-headed and Bronzed Cowbirds and Rusty (Euphagus

STEVE N. G. HOWELL

Figure 5. Heads of Shiny (left), Brown-headed (middle), and Bronzed (right) Cowbirds. The proportionately thinner and more pointed bill of the Shiny Cowbird, compared with the more conical bills of the other two species, is a subtle but distinctive field mark. Brown-headed Cowbirds have a more rounded head and steeper forehead than Shiny or Bronzed Cowbirds, although this feature depends upon posture to some extent. This illustration, by Steve N.G. Howell, is used with permission from Identification Guide t o Nor th American Birds by Peter Pyle (1 997).

SHINY COWBIRD

one photographed at the Dry Tortugas in April 1997, are very dark, appearing neorly black in poor 1ight.This female nearly lacks a paler supercilium and appears to have only a small paler area at the throat.Again, note the thin, point- ed bill; the whitish streak on the lower mandible appears to be an artifact of the camera flosh.

carolinus) and Brewer's (E. cyanocephalzis) Blackbirds by their all-black plumage and dark eyes. Adult males (i.e., in their third calendar year and older) are completely black, with bluish or purplish iridescence through- out the body (Figure 2). The head becomes more bluish with feather wear (Lowther and Post 1999). First-year males (Figures 6 and 17) are similar to adults, but retain some brown feathers from juvenal plumage on the body, wings, and tail (Grzybowski and Fazio 1991, Lowther and Post 1999). Because males are easy to identi- fy, it is perhaps not surprising that every first-state and first- provincial report of Shiny Cowbirds in the ABA Area has involved one or more males.

Female Shiny and Brown- headed Cowbirds are difficult to separate, but identification is possible with care and experi- ence, and under ideal viewing conditions (Figures 1,7, 8, and 9). Bill shape and head shape are distinctively different (Smith and Sprunt 1987, Jaramillo and Burke 1999). The pale base of the lower mandible, when pre- sent, is also diagnostic of Brown- headed Cowbird (Jaramillo and Burke 1999). Plumage differ- ences between the two are slight

Figure 7. Female Shiny Cowbirds vary in color, but most are darker overall than female Brown-headed Cowbirds. Many ore similor in color to femole Bronzed Cowbirds, but their irides are always dark. Some female Shinies, such as this

(Smith and Sprunt 1987, Jaramillo and Burke 1999, Lowther and Post 1999), but a few have been noted as possibly useful in the field. The female Shiny is darker overall, with a more prominent supercilium, darker eye-stripe and auriculars, and a darker, less-contrasting throat (Smith and Sprunt 1987, Jaramillo and Burke 1999). Female Bronzed Cowbirds

LARRY SANSONE

(Figure 10) are easily identified by their red or reddish irides (Pyle 1997, Jaramillo and Burke 1999).

Another identification chal- lenge is posed by the female Brewer's Blackbird (Figure 1 I), which is only slightly larger and very similar in plumage. Howevel; the bill of the black- bird is grayish, not dark, and it is longer and thinner. Blackbirds

KEVIN T. KARLSON

Figure 8. Most female Shiny Cowbirds are considerably lighter than the individual in Figure 7. This classic female, photographed at the Dry Tortugas in April 1999, shows a prominent pole supercilium, pale throat, characteristic bill shape, slim body, long tail, ond beady block eye.

BIRDING. DECEMBER 2000

BRIAN E SMALL

Figure 9. Female Brown-headed Cowbirds are usually dull brownish overall. The bills of Brown- headed Cowbirds are the most conical of the three species under discussion, as is apparent here. Some femoles have a pale base to the lower mandible, but this one has an all-blackish bill. Brown-headed Cowbirds from the western part of the ABA Areq such as this femole, have heads paler than the rest of the body.Again, note the overall body shape, with rounded head, stocky body, and short toil.This femole was photographed in southern California in May 1998.

BRIAN E. SMALL

Figure 10. Of the two subspecies of the Bronzed Cowbird found in the ABA Areo, femoles of M.a, aeneus have all-black plumage, while femoles of M.a. loyei are grayish overall with a whitish throat. This female M.a. aeneus photographed at South Padre Island, Texas, in May 1998 shows dull but noticeable iridescence throughout the body. The iris color of Bronzed Cowbirds varies in intensity, but always is a shade of red; adults can be distinguished from all other icterids in the ABA Areo by this feature alone.

SHINY COWBIRD

shape differs from that of cow- birds. Female Brewer's Blackbirds show iridescence on the wings and tail, a feature shared with some very dark female Shiny Cowbirds (Jaramillo and Burke 1999).

Identification criteria for cow- birds in juvenal plumage are still being developed. The sexes of Shiny Cowbirds of the minimus subspecies are nearly identical in juvenal plumage, while all other subspecies exhibit clear sexual dimorphism (Friedman 1929, Jaramillo and Burke 1999). Juveniles of minimus are largely unstreaked below, with brown- ish-buffy upperparts and pale fringes to the flight feathers and wing coverts. The throat and supercilium may be quite buffy (Figure 12). In contrast, juvenile Brown-headed Cowbirds are heavily streaked below, and brownish-gra y above, with paler edges to the wing feathersand wing coverts (Figure 13). The bills of juvenile Shiny Cowbirds are usually all-dark, while those of Brown-headed Cowbirds range from all-dark to extensively pale (Jaramillo and Burke 1999.

The courtship song of the Shiny Cowbird consists of three to five low, bubbly purr notes followed by two or three high notes. A more complex "twitter song" consists of three introduc- tory notes followed by a twitter (Friedmann 1929, Jaramillo and Burke 1999, Lowther and Post 1999). The twitter song, which sounds like the song of a canary (D.B. McNair, pers. comm.), is the basis for the popularity of Shiny Cowbirds as cagebirds in parts of South America and the West Indies. A rapid chattering call is given mostly by females. The common call is a low chuck

519

possible anywhere

(Jararnillo and Burke 1999, Lowther and Post 1999), but Shiny Cowbirds also have a call note like that of the Solitary Sandpiper (Tringa solitaria; D.B. ~McNair, pers. comrn.).

P. William Smith (pers. comm.) has never heard the courtship song of the Shiny Cowbird in Florida, but the twit- ter song is "fairly frequent." Post et al. (1993) have "often" heard males sing the twitter song in Florida and South Carolina, but they do not mention the courtship song. A male at Lake Apopka, Florida, in February 2000 also sang the twitter song (K. Radamaker, pers, comm.). In Florida, Smith (pers. comm.) has heard male Brown-headed Cowbirds mimic the twitter song "perfectly" when in the presence of female Shiny Cowbirds! Recordings of the Shiny Cowbird courtship song and chatter call, but unfortunately not the twitter song, are available on Bird Songs of Florida (Keller 1997).

520

LARRY SANSONE

Figure I I . Even though Shiny Cowbirds have not yet been found within the breeding range of the Brewer's Blackbird, both species winter in Florida, albeit usually in dif- ferent regions. Similarities in plumage may cause on out-of- range Shiny Cowbird to be overlooked as a Brewer's Blackbird. The blackbird is only slightly larger than cowbirds, but note the slender bill and brownish iris. Female Brewer's Blackbirds show iridescence on the wings and toil, which is shored with some female Bronzed and Shiny Cowbirds. This female Brewer's Blackbird was photographed in Los Angeles County, California, in lonuory 1990.

EDUARDO VENTOSA

Figure 12. This juvenile minimus, shown with an adult male, has virtually unstreoked underparts with a buf i breast and pole gray belly and undertoil coverts. The wing coverts ore brownish, edged with buR; and the wings show two indistinct b u n wing-bars. The head is rich brownish, with o buf i throat and conspicuous buf i supercilium. Note also thot the juvenile's bill shape and color mirror the mole's. If this is a typical juvenile min- imus Shiny Cowbird, its identification may be fairly easy compared to thot of other juve- nile cowbirds in the ABA AreaThese Shiny Cowbirds were photographed in Puerto Rico in February 1999.

BIRDING. DECEMBER 2000

Figure 13. This juvenile Brown-headed Cowbim photographed in central Montana in June 1997

differs substantially from the juvenile Shiny Cowbird in Figure 12. It is a plain grayish-brown on the wings and back, with pale feather edges

on the wing coverts and mantle.The pale brown underparts with distinct blackish streaking are

typical ofjuveniles. Note also the rounded head, short tail, and conical bill, which is all blackish in this individual; the bills ofjuvenile Brown-headed

Cowbirds often are pale at the base, sometimes extensively so. I

MEXICO

BRIAN E. SMALL

GULF

OF Mr

MEXICO

ATLANTIC b

BERMUDA

OCEAN

Grand Bahama

L .

L Grind*

Cayman , JAMAICA

E

\

0 single report multiple reports

A - a Grenada,

Figure 14. Deforestation of Caribbean islands for agriculture and animal husbandry allowed Shiny Cowbirds to spread throughout the West lndies in the past 100 years.The first record, from Vieques Island (east of Puerto Rico) in 1860, may have been an escaped cagebird, but all later reports are probably the result of"is1and-hopping"invasion. Shiny Cowbirds were recorded first in the Grenadines in 1899, at Barbados in

-1 9 16, Martinique in 1948, Puerto Rico in 1955, the Dominican Republic in 1972, Haiti in 1980, Cuba in 1982, the United States in 1985, '( 'Canada and Jamaica in 1993. the Bahamas (Andros) in 1994, Grand Cayman in 1 995. and Mexico (Yucatan) in 1 996. The current range of .! Shiny Cowbird outside the ABA Area is shaded in pink an the map. Coastal areas of the U.S. with multiple reports a short distance apart are

shaded in red, while scattered reports are indicated as isolated dots. Principal sources of reports: American BirdslNational Audubon Society '! Field NoteslField NoteslNorth American Birds and Florida Field Naturalist Cruz et al. (1 985); Post (1 992); Post et d (1 993); Beno-

(1 995); Kluza (1 998); Raffaele et 01. (1 998); Lowther and Post (1 999).

SHINY COWBIRD

possiblr anywh--

Figure IS. Shiny Cowbirds reported in all months in the ABA Area. Because Shiny Cowbirds have remained at some sites for weeks or montns, ony me single highest count has been used for each site per year or per season. Birds observed at a site at least three months later than the most recent previous report were considered different indi- viduals, and were counted. In the data columns, the first number is the number of reports, and the second is the number of individuals. No number denotes no reports. For those reports that did not list the number of individuals observed, it was assumed that one bird was seen. Data are taken from the seasonal reports in American BirdslNational Audubon Society Field NoteslField NotedNorth American Birds through 1999 (reports questioned by regional

;'< editors ore not included); Field Observations reports in Florida Field Naturalist beginning with the Winter 1989-1 990 season through 1999; Florida Christmas Bird Count reports from the BirdSource website ~http:/lbirdsource.cornell.edulcbc*; and reports in Post (1 992), Post et al. (1993), and Benoit ( I 99S).Abbreviations:Alaboma (AL), Florida (FL), Georgia (GA), Louisiana (LA), Maine (ME), Mississippi (MS), New Brunswick (NB), North Carolina (NC), Oklahoma (OK), South Carolina (SC), Tennessee (TN), Texas (TX), and Virginia (VA).

Figure 16. Shiny Cowbirds reported in the ABA Area duringApri1, May,june, andJuly. Abbreviations and information concerning data are the same as for Figure IS.

1 Totals ~16162~1031415~ 9/10 ll~161 111 1 111 1 9110 1 111 111138 1 111 1 515 11691560 1

At Fort De Soto County Park, Florida, Lyn Atherton (pers. comm.) has noticed different for- aging behaviors between Shiny and Brown-headed Cowbirds. In every instance when she has observed Shiny Cowbirds feed- ing, they have been actively hunt- ing for insects, often running about while chasing them down. Brown-headed Cowbirds, in con- trast, feed "rather calmly" on

522

seeds. Only once, in fall, has Atherton observed a Brown- headed Cowbird feeding on insects at the park. Considering the greater proportion of animal matter in the Shiny Cowbird's diet compared to the predomi- nantly vegetarian diet of the Brown-headed Cowbird (90 per- cent versus 25 percent: Lowther 1993, Lowther and Post 1999), this active foraging behavior of

BIRDING. DECEMBER 2000

the Shiny Cowbirds might be expected, and may be a useful indicator for identifying female and juvenile cowbirds away from bird feeders.

Occurrence in North America Shiny Cowbirds have been reported from 13 states and provinces (Figure 14).The first individual in the ABA Area was found at Lower Matecumbe Key, Florida, from 14 June to late July 1985. The following year, in July 1986, three males were pho- tographed nearby at Islamorada (Smith and Sprunt 1987). Birds reached the Florida mainland at Flamingo in 1987, and were found as far north as St. Petersburg and Jacksonville in 1988 (Post et al. 1993). Florida reports continued to increase rapidly, with single-day totals of up to 44 birds at Key West and 52 at Dry Tortugas National Park in spring 1989 (Langridge 1989). That same year, Shiny Cowbirds were observed in the Florida Panhandle, as well as in Georgia, Louisiana, North Carolina, and South Carolina. First-state reports were obtained for Alabama (at least 41 birds!), Oklahoma, and Texas in 1990, and Maine and Mississippi in 1991 (Post et al. 1993). In August 1993, a male cowbird was photographed in New Brunswick (Benoit 1995), the first and only report so far for Canada. Tennessee's first Shiny Cowbird was a male in July 1995 (Purrington 1995), fol- lowed by Virginia's first in fall 1996 (Iliff 1997). A male in Yucatan, Mexico, in May 1996 (Kluza 1998) is the first Middle American report outside of Panama. In July 1999, 18 Shiny Cowbirds were found at

Savannah Spoil Site, South Carolina (P.W. Sykes in Davis 1999), which represents the largest number of individuals yet reported along the Atlantic coast. Thirteen of these cowbirds were collected, and the remaining five disappeared on their own. In the summer of 2000, Shiny Cow- birds were again found in this area, but the number of individu- als was ~nuch smaller than the year before (P.W. Sykes, pers. comm.).

Figure 15 sunmarizes Shiny Cowbird reports by year and state/province, revised and updat- ed from Mlodinow and O'Brien (1996). I have excluded eight or nine Texas reports in 1994 that were submitted to the National Audubon Society Field Notes regional editors without docu- mentation (Lasley et al. 1994). Through 31 December 1999, there have been 246 reports of 959 Shiny Cowbirds in the ABA Area. Florida accounts for 64 percent of the reports and 82 percent of the individuals. Alabama is the only other state that accounts for any significant number of Shiny Cowbirds, with 6 percent of the individuals, As a means of determining the degree to which Shiny Cowbirds may threaten our breeding passerines, I have also segregated out the reports from April through July (Figure 16), the months that rep- resent the nesting season for most North American passerines. ABA-Area totals for these months are 169 reports of 560 individuals. Florida again accounts for a majority of the reports (61 percent) and individ- uals (74 percent). Alabama accounts for 11 percent of the individuals reported, while South Carolina accounts for 6 percent.

During its first five years in the

SHINY COWBIRD

Figure 1 7. This first-year male Shiny Cowbird, cap-

tured in a trap in the Wichita Mountains,

Oklahoma, on 12 june 1990, documents the

westernmost occurrence to date of the Shiny Cowbird

in the ABA Area.The brown feathering on the breast

and flonks-characteristic of this plumage-is con-

spicuous at close range but may not be visible

from a distance. Out of direct sunlight, the

plumage is less iridescent This photograph affords an

excellent look at the bill, which is less conical than

those of Brown-headed and Bronzed Cowbirds.

ABA Area (1985-1989) the Shiny Cowbird rapidly invaded coastal areas of Florida. The number of individuals reported increased markedly every year, and the first reports from other southeastern states occurred in 1989 (Figure 15). In 1990, numbers in Florida were much reduced from the pre- vious year, but Alabama saw a substantial invasion. By 1995, Shiny Cowbirds had reached a total of a dozen states, and one bird even made it to Canada, but numbers in the Southeast remained low. Since 1985, the mean number of Shiny Cowbirds reported in Florida from April through July is 27 individuals annually (Figure 16). Elsewhere, Shiny Cowbirds have been reported fairly frequently during those months only in Alabama, Louisiana, and the Carolinas, with sporadic reports from other states. Usually only one to three birds are reported annually in

JOE GRZYBOWSKI

any state outside of Florida (Figure 15). Since 1996, no new state or province has been invad- ed, and cowbird occurrences in Florida and elsewhere have remained virtually restricted to coastal areas. Where these birds go after they "disappear" from coastal areas has not been deter- mined. Shiny Cowbirds winter regularly in the ABA Area only in the southern half of the Florida peninsula (Post et al. 1993), a fact which suggests that climate may be a limiting factor in their occurrence in North America-at least outside the breeding season.

Conclusions Within a few years of its debut in Florida, most observers would have agreed that the Shiny Cowbird would soon be possible anywhere in the ABA Area, and many attempted to estimate the speed at which cowbirds would

523

possible anywhere

spread across the United States. Kaufman (1990) predicted that --- they would reach-~alifornia e before 1995, based on a single bird captured at Fort Hood, X - Texas, in May 1990. However,::::: - --.. in the past 10 years only one 2 Shiny Cowbird has been found?' farther west than Fort Hood, and that bird was captured in "' Oklahoma in June 1990 ( ~ i ~ u r - 17). The fact is that today, 15 vears after its discovery in t b kBA Area, the Shiny Cowb

resident in small numbers ir souther] lorida and rar where.

What must you do ro see a Shiny Cowbird? Since the mid- 1990s, all reliable sites have been in Florida. In spring and summer, birds are reported annually from Dry Tortugas National Park, Key West, and Flamingo. In winter, Shiny Cowbirds are found most readily at Briggs Nature Center south of Naples, with other indi- viduals usually present at Key Vest and Homestead. Many

observations have been at bird feeders, especially during the winter months, or in suburban areas along roads and on lawns (Post et al. 1993, Stevenson and Anderson 1994). In countries where they are common, Shiny Cowbirds sometimes forage with livestock. They frequently associ- ate with other icterids, so scan carefully through flocks of black- birds and Brown-headed Cowbirds. Look sharply; Shiny Cowbirds can easily be missed.

Is this still a species to be expected nearly any place in the U.S. or Canada? Probably not, if one considers only the pattern of occurrences in the past decade. But the long-range outlook may be different. A tendency for range expansions, enabled by brood parasitism, appears to be

1st 2nd 1st 2nd 1st 2nd 1st 2nd 1st 2nd 1st 2nd 1st 2nd 1st 2nd 1st 2nd 1st 2nd 1st 2nd 1st 2nd Jan Jan Feb Feb War Mar Apr Apr May May Jun Jun Jul Jul Aug Aug Sep Sep Oct Ocl Nov Nav Dec Dec I

:igure 18. Numbers of Shiny Cowbird reports (gray bars) and individuals (black bars) in the MA Area, through December 1999, are charted by the date of first observation and arranged ~y half-month intervals. Reports that did not specify a date are excluded, although observa- ions "early" or "late" in a month are included in the appropriate column. Note the huge influ- ~f Shiny Cowbirds from mid-April through the end of May, a trend also apparent-though far ~ s s dramatically-in the number of reports. The increase of individuals beginning in mid- 7 hober reflects Shiny Cowbirds returning to wintering areas in southern Florida. "Increases" z L iom mid-December through earlyjanuary mostly represent an observer bias from Christmasm--' )ird Counts.

I cowbird trait. Molecular evi- lence indicates that the grackles md their allies-the subgroup of cterids to which cowbirds ~elong--evolved in North and l/liddie America and the z-z

.-., -.A - Zaribbean (Johnson and Lanyon 1999). Except for the cowbirds, 111 the species within this group Oemain restricted to those areas, md none is an obligate brood Jarasite. In contrast, Screaming, Siant, and Shiny Cowbirds pre- ;uma bly colonized South 4merica in the remote past. jhiny and Brown-headed zowbirds also have expanded :heir ranges aggressively in his- :orical times, in response to ha bi- :at alterations by humans, as lave Bronzed Cowbirds to a less- :r degree. Shiny Cowbirds appar- :ntly are still increasing in Cuba, :he Bahamas, and Panama. As ~opulations increase, so does the Jotential for renewed northward :xpansion, heralded by the spike n annual arrivals of this species

in the ABA Area in late April and May (Figure 18). Perhaps it is only a matter of time before the Shiny Cowbird is indeed pos- sible anywhere on the North American continent.

Acknowledgments I thank Lyn Atherton, Wes Biggs, Greg Jackson, Larry Manfred;, Kurt Radamaker, Paul Sykes, Eddie Ventosa, Rick West, and Glen Woolfenden for relating their field observations, and Terry Moore, lMichael Patten, and Will Post for other information. Bruce Anderson Mike Delany, Don Forrester, Mark- - Oberle, and Glen Woolfenden pro-: vided references or helped t r a c c . ̂-- down photographs, and Holly a -

Love11 assisted with library work. I am most grateful to Bruce Anderson, Jon Dunn, Greg Jackson, Peter Lowther, Doug McNair, Steve Mlodinow, P. William Smith, and Noel Warner for greatly improving (way too many) drafts of the manu- script. For support, I thank Mike Delany and staff a t Avon Park Air Force Range.

BIRDING. DECEMBER 2000

Literature Cited American Ornithologists' Union. 2000.

Forty-second supplement to the A~ncrican Ornithologists' Union Check-list of North American blrds. Arrk 117: 847-858.

Baicich, P.J., and C.J.O. Harrison. 1997. A Guide to the Nests, Eggs, aird Nestliitgs of N o ~ t h Anterican Birds. 2d ed. Academic Press, San Diego.

Benoit, G. 1995. A day to remember:

T H E E V O L U T I O N OF OPTICS.

first Shiny Cowbird in Canada. Birders Jorrrnal4: 230-231.

Blake, E.R. 1968. Family Icteridae. 111 R.A. Paynter, Jr., ed. Checklist of Birds of the \VorId. v.14. Museum of Comparative Zoology, Harvard University.

Cruz, A., W. Post, J.W. Wiley, C.P. Ortega, T.K. Nakamura, and L.W. Prather. 1998. Potential impacts of cowbird range expansion in Florida. In S.I. Rothstein and S.K. Robinson, eds. Parasitic Birds and Their Hosts:

Strrdies in Coeuoltrtion. Oxford University Press.

Davis, R. 1999. Southern Atlantic Coast region. North Anzerican Birds 53: 375-376.

Frkdmann, H. 1929. Tlw Cotubrrds: A Study in the Biology of Soc~al Prrr~7sitisnz. C. Thomas Publications. Springfield, Illinois.

Grzybowski, J.A., and V.W. Fazio 111. 1991. Shiny Cowbird reaches Okla- homa. Aiizerrwrz Birds 45: 50-52.

Iliff, M. 1997. Mid-Atlantic region.

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