Spotlight on Zoo Science
May 5, 2004
Winter Challenge for Golden-cheeked Warblers
A National Zoo scientist's range-wide analysis of habitat for a migratory bird, the first of its kind, provides clues to conservation.
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A Golden-cheeked Warbler. |
Led by the Smithsonian’s National Zoological Park scientist John Rappole, scientists from the U.S. Forest Service’s Northeast Forest Experiment Station at the University of Massachusetts, the University of Georgia’s Institute of Ecology, and the University of Mexico’s Instituto de Biologia have performed the first analysis of total breeding and wintering habitat for any migratory bird species.
Using a combination of satellite imagery, geographic information system (GIS) procedures, and three field seasons of ground surveys in Mexico, Guatemala, and Honduras, they assessed the winter distribution, habitat use, and density of the Golden-cheeked Warbler (Dendroica chrysoparia), an endangered migratory species that breeds only in central Texas. They combined these data with similar information gathered by the U.S. Fish & Wildlife Service from the bird’s Texas breeding range to obtain the range-wide habitat estimates.
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The team discovered that total amounts of the species’ cedar-brake breeding habitat in Texas and its highland pine-oak winter habitat in Mexico and Central America were nearly equivalent, with roughly 6,500 square kilometers (about 2,500 square miles) of each.
However, the density of birds that each habitat could support appeared to be radically different, with an estimated 228,000 birds for the Texas breeding habitat and only 34,000 birds in the tropical winter habitat. The actual population estimates for the bird are close to 34,000, about matching the number that tropical winter habitat supports.
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| Wintering habitat, shown in this satellite image, can support only about 34,000 Golden-cheeked Warblers. |
appole notes that the findings have implications for the Golden-cheeked Warbler and migratory bird species in general. “Scientists have long speculated that winter habitat availability could limit migrant populations,” he notes. “However, this study presents the first data documenting that possibility. In addition, it emphasizes the need for a more balanced approach to conservation efforts.
Historically, nearly all conservation dollars have been focused on the breeding portion of the life cycle of avian migrants. This study shows that comparable efforts need to be directed toward wintering ground conservation—at least for the Golden-cheeked Warbler, and perhaps other endangered migrants as well.”
—John Rappole
Note to Media: If you would like more information about this project, or any of the Zoo's conservation and science programs, please contact the Zoo's Office of Public Affairs.
