Meeting Abstract

P1.7  Thursday, Jan. 3  Effects of heavy rainfall on the physiology and life-history of migratory songbirds breeding in the south-central United States. BUTLER, Luke K*; HAYDEN, Timothy J; ROMERO, L. Michael; Tufts University; Army Endangered Species Research Program; Tufts University luke.butler@tufts.edu

We took advantage of sequential years of very low and very high rainfall to test the hypothesis that an increase in primary productivity would correlate with an increase in adult body condition and reproductive success in two insectivorous passerines breeding sympatrically in Texas, United States. Because extended reproductive effort is correlated with delayed start of the post-breeding molt, we also compared the timing of the onset of molt between dry and wet years. We compared the white-eyed vireo (Vireo griseus), which breeds in a wide range of brushy habitats throughout the eastern United States, to the endangered black-capped vireo (V. atricapillus), which prefers to breed in relatively rare habitat: deciduous scrub interspersed with open rocky ground. Therefore we also tested the hypothesis that a habitat generalist and a habitat specialist would be affected in the same way by increased precipitation. We used size-corrected body mass as our measure of adult body condition, and age ratios of captured birds as an index of reproductive success. Onset of molt was estimated by comparing the frequency of molters over the same time period in early summer. This study illustrates physiological and life-history effects of precipitation on small, insectivorous, migratory birds.