GOLDEN-CHEEKED WARBLER NEST MORTALITY AND PREDATORS IN URBAN AND RURAL LANDSCAPES

摘要

Predation is a major cause of nest failure for songbirds, yet information is lacking on the relative importance of predator species in different landscapes. We identified nest predators of Golden-cheeked Warblers (Dendroica chrysoparia) in an urban landscape, compared cause-specific mortality rates between urban and rural landscapes, and evaluated whether monitoring nests with cameras affected nest survival. We monitored 68 nests with cameras in Austin, Texas, during 2005, 2006, and 2008 to identify causes of mortality, including predators, in an urban landscape. The period mortality and predation rates were 0.60 (95% CI: 0.42-0.73) and 0.52 (95% CI: 0.37-0.68), respectively. We identified predators at 20 nests: Texas rat snakes (Elaphe obsoleta lindheimerii) depredated eight nests (40%), Western Scrub-Jays (Aphelocoma californica) depredated six (30%), Cooper's Hawks (Accipter cooperii) depredated two (10%), fox squirrels (Sciurus niger) depredated three (15%), and fire ants (Solenopsis sp.) depredated one nest (5%). We compared mortality rates, predation rates, and predators of the 68 camera-monitored nests in Austin to 74 nests monitored with cameras in the rural landscape of Fort Hood, Texas, during 1997-2002 and 2005. The period mortality rate (0.63, 95% CI: 0.47-0.75), predation rate (0.59, 95% CI: 0.45- 0.73), and predator composition at Fort Hood were similar to those in Austin. Nest abandonment, hatching success, and nestling survival were also similar in both landscapes. We compared nest survival of the 68 camera-monitored nests to 62 active nests monitored without video cameras in Austin, period nest survival was slightly higher for camera-monitored nests (0.40, 95% CI: 0.22-0.58) than for nests without cameras (0.37, 95% CI: 0.19-0.54).