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Migratory Bird Conservation at Fort Hood.

Fort Hood, a major Army training base located on approximately 220,000 acres (88,000 hectares) in central Texas, supports the largest known breeding populations of the endangered black-capped vireo (Vireo articapillus) and golden-cheeked warbler (Dendroica chrysoparia) under any single property management. Both birds have very small breeding ranges--black-capped vireos nest in central Texas and southern Oklahoma, while golden-cheeked warblers nest only in central Texas.

They also have specialized habitat needs. Black-capped vireos require hardwood scrub habitat consisting of patchy shrubs and thickets interspersed with live and dead trees. Golden-cheeked warblers require mixed hardwood stands consisting of ash juniper and a variety of oak species. Habitat loss is a major threat to the survival of both species. However, nesting failure due to nest parasitism by brown-headed cowbirds (Molothrus ater) has been the main factor in the decline of the black-capped vireo and is likely to be a significant factor affecting the warbler.

An active cowbird control program at Ft. Hood has reduced the parasitism problem from a documented loss of 92 percent of black-capped vireo nests in 1988 to less than 20 percent for the past three years, and less than 10 percent for 1997. Although rates for the golden-cheeked warbler were not studied, cowbird control is assumed to have helped this species as well. Both populations are now healthy, growing, and appear to be sustainable, which was not the case before the cowbird control program was started. There are currently estimated to be more than 400 nesting pairs of black-capped vireos and 2,000 nesting pairs of golden-cheeked warblers on the base.

Ft. Hood is using a variety of technologies to monitor the birds, including video cameras, satellite imagery, global positioning systems (GPS), and radio telemetry. For example, miniature video cameras recently detected for the first time the region's non-native fire ants preying on a nest of black-capped vireos. In another project, miniature transmitters are being affixed to the cowbirds to monitor the birds' movements. This information has been invaluable in helping managers from Ft. Hood and researchers from The Nature Conservancy formulate a recovery plan for the vireos and warblers by delineating where cowbirds feed and congregate. A GPS is used to pinpoint vireo and warbler nest locations, and a Geographic Information System helps define patterns of data on topography, vegetation, and species occurrences.

What sets Ft. Hood apart is its successful ability to integrate a range of technological applications with on-the-ground management. For example, data collected during the 1997 nesting season suggest a strong relationship between the distribution of cattle and the frequency of cowbird parasitism. Managers recognize that removing cattle from vireoand warbler habitat may not be practical given the economic realities of central Texas. But researchers from The Nature Conservancy have recommended that Ft. Hood develop grazing practices that rotate cattle out of the habitat during the nesting period. This would not only benefit the endangered birds but also provide more forage for the cattle after the nesting season. If successful, this long-term management solution could successfully accommodate both people and birds without adversely affecting the military mission.

L. Peter Boice is Director, Conservation, Office of the Deputy Under Secretary of Defense (Environmental Security). The Department of Defense manages 25 million acres (10.1 million ha) of public lands in support of the military mission by providing for the sustained use of its land, sea, and air resources; protecting valuable natural and cultural resources for future generations; meeting all legal requirements; promoting compatible multiple uses of resources; and managing resources in a cost-effective manner.
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Title Annotation:Texas
Author:Boice, L. Peter
Publication:Endangered Species Bulletin
Geographic Code:1U7TX
Date:Jul 1, 1998
Words:589
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