SPRING 2001/VOLUME 15, NUMBER 2

Cornell Lab of Ornithology
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Golden-winged Warbler Atlas Project
Cerulean Warbler Atlas Project

GOWAP participants find unusual hybrid plumages

Launched in the spring of 1999, the Golden-winged Warbler Atlas Project (GOWAP) is attempting to determine the population status and distribution of the Golden-winged Warbler. This species has declined in numbers significantly throughout its range, primarily because of range expansion and encroachment of the closely related Blue-winged Warbler.

Where their ranges overlap, you may find a "Brewster's Warbler" or the lesser-known "Lawrence's Warbler," which are hybrids resulting from a pairing between Golden- and Blue-winged warblers. A great deal of variation exists in these hybrids reflecting the interactions between dominant and recessive genes. The white underparts of a golden-winged and the reduced facial pattern or black eye-line of a blue-winged are dominant traits, whereas the yellow underparts of the golden-winged and the broad facial pattern showing black ear and throat patches are recessive traits. "Brewster's Warblers" exhibit the dominant traits, and "Lawrence's Warblers" exhibit the recessive traits. Just as people with the recessive trait of red hair are relatively uncommon, the comparative rarity of the "Lawrence's Warbler" is the result of a naturally rare combination of recessive genes. See Peterson's Field Guide to Warblers by Dunn and Garrett for more details.

These genes interact in ways we don't yet fully understand. During GOWAP's Spring 2000 field season, participants spotted several birds with unusual plumage near Upstate New York's Cayuga Lake basin. One had the overall appearance of a Blue-winged Warbler but with a ragged black throat-patch. A similar bird had its otherwise yellow throat covered with large black spots. These rare plumage types do not fit any field guide descriptions. John Confer, associate professor of biology at Ithaca College, says these plumage types suggest there may be more than two pairs of genes involved in determining plumage variations between Blue-winged and Golden-winged warblers. Studying these unusual hybrids may help us understand the genetic basis of the hybridization between these two species. And because these birds sing hybrid songs, we may be able to explore the role of heredity in the birds' song formation.

The data from GOWAP will be used to create accurate maps of the hybrid zone and illuminate the factors that affect the distribution of the Golden-winged Warbler. The numerous volunteers contributing data to GOWAP make invaluable contributions to this understanding and will play an important role in the conservation of this rare species.

Please consider joining the GOWAP research team this spring. We need more participants in all areas where Golden-winged and Blue-winged warblers breed. For more information or to sign up return the enclosed coupon, call (607) 254-2465, or send e-mail to <forest_birds @cornell.edu>. And be sure to visit our web site at <birds.cornell.edu/gowap>.