Postbreeding Habitat Use by Golden-Cheeked Warblers (Setophaga chrysoparia)

Abstract

The period following breeding but prior to migration is an important, though understudied, component of the avian annual life cycle. We quantified habitat use by endangered Golden-cheeked Warblers (Setophaga chrysoparia) during the postbreeding period in Golden-cheeked Warbler breeding habitat (i.e., oak-juniper [Quercus-Juniperus] woodlands) predominated by Texas oak (Quercus buckleyi) or post oak (Q. stellata), as well as in immediately adjacent oak woodland, oak savanna, and riparian vegetation not usually associated with breeding activity for this species. Most (87%) of the Golden-cheeked Warblers we detected were in oak-juniper woodlands, especially in Texas oak sites, but we also detected warblers in each of the other vegetation types we surveyed. Adults and family groups used breeding and nonbreeding habitat similarly, as did males and females, but juveniles used nonbreeding habitat more than adults did. Neither canopy cover nor territory density during the breeding season influenced postbreeding habitat use by warblers, regardless of vegetation type. We detected warblers 82% less often in post oak breeding habitat than in Texas oak breeding habitat despite similar densities of breeding territories, suggesting that warblers left post oak sites earlier during the postbreeding period. However, we found no evidence that warblers that bred in post oak sites were more likely to move into adjacent nonbreeding habitat than those that bred in Texas oak sites. Ashe juniper (Juniperus ashei) was the most consistently used woody substrate during the postbreeding period, regardless of warbler sex, warbler age, habitat type, or predominant oak species. Our results emphasize the continued importance of oak-juniper woodlands to Golden-cheeked Warblers during the postbreeding period but suggest that other vegetation types may also have conservation value for this species.