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Tuesday, June 20, 2006

Birds of the Mid-Atlantic #13: Golden-winged Warbler

In the Birds of the Mid-Atlantic series so far I have covered only birds that I have seen myself. One eastern bird that I have not seen but would very much like to see is the golden-winged warbler. Golden-winged warblers breed in a wide band across the upper midwest and southern Canada (see BBS map). In the mid-Atlantic region, one is most likely to find them breeding in the middle and higher elevations of the ridge and valley province. During spring and fall migration the birds may be seen over a much wider area.

Males have a bold black and white facial pattern with a yellow cap and yellow wing coverts. Females have the yellow coverts but without as bold of a facial pattern. Golden-winged warblers behave much like chickadees, as they forage energetically and occasionally hang upside-down. The golden-winged song resembles that of the blue-winged warbler, but with a repeated second syllable.

Golden-winged Warbler / Photo by Ron Austing (NPS)

Like cerulean warblers, golden-winged warblers are in steep decline, enough to get the species red-listed on the Audubon Watch List. The causes for this warbler's decline are similar to those of other eastern songbirds, with habitat loss leading the list. Golden-winged warblers favor early successional habitats, which are associated with human disturbance such as old fields and power line cuts. As old fields grow into mature woodland, the lost habitats are often not being replaced by new old fields due to land use changes.

Some of the decline is attributable to other bird species. Birds nesting in edge and early successional habitats are especially vulnerable to brown-headed cowbirds, and the golden-winged warbler is no exception: about 30% of this species's nests receive cowbird eggs. Hybridization and competition with blue-winged warblers (yellow-listed on the Audubon Watch List) may also contribute. Blue-winged warblers are steadily invading the golden-winged's former range. Where the two species overlap, hybrids are common. A first-generation hybrid (i.e., blue-winged X golden-winged) is known as a Brewster's warbler; second generation backcrosses result in the Lawrence's warbler, which is much rarer. As blue-winged warblers enter the territories of golden-winged warblers, the latter slowly are pushed further north.

How can birders help? One way is to report sightings and participate in research programs that will guide conservation efforts. The Cornell Lab of Ornithology is conducting a multi-year Golden-winged Warbler Atlas Project to determine the breeding distribution and habitat requirements for the species. This year's project is drawing to a close, but the opportunity to participate will probably be open again in future years. Many local bird clubs, ornithological societies, and government agencies may also be able to use sighting information. (West Virginia, for example, asks for reports.) If you have seen either blue-winged or golden-winged warblers outside of the United States and Canada, you can send this information to the Alianza Alas Doradas.

Crossposted at the A DC Birding Blog.



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