TREE SPECIES COMPOSITION AND FOOD AVAILABILITY AFFECT PRODUCTIVITY OF AN ENDANGERED SPECIES: THE GOLDEN-CHEEKED WARBLER

摘要

Vegetation characteristics affect avian reproductive success for a variety of reasons, including predators, nesting sites, song perches, and food availability. We investigated the relationship between habitat composition and prey availability and the effect these variables have on reproductive success in the Golden-cheeked Warbler (Setophaga chrysoparia). Our objectives were to determine differences in pairing and fledging success of Golden-cheeked Warbler territories in two distinctive vegetation types and to explore the relationship between reproductive success and tree species composition, arthropod density, and foraging effort. We sampled in 2009 and 2010 at Fort Hood, north-central Texas, within 347 territories of two vegetation types: post oak (Quercus stellata) habitat and Texas oak (Q. buckleyi) habitat. Pairing and fledging success of territories was significantly higher in Texas oak habitat. The birds' rate of movement was considerably higher in post oak habitat, indicating a difference in prey-encounter rate. Golden-cheeked Warblers clearly switched substrates on which they foraged from oaks in April to juniper in May. Arthropod sampling revealed a correlation between preferred foraging substrates and arthropod density. Our study of foraging indicates that the interplay between tree species and the arthropod communities they support is a crucial element driving the Golden-cheeked Warbler's reproductive success.