Physical Sciences and Mathematics Commons^™

Steroid Hormone Levels Are Related To Choice Of Colony Size In Cliff Swallows, Charles R. Brown, Mary Bomberger Brown, Samrrah A. Raouf, Linda C. Smith, John C. Wingfield

School of Natural Resources: Faculty Publications

One hypothesis to explain the extensive variation in colony size seen in most
taxa is that individuals sort themselves among groups based on phenotypic characteristics
that correlate with their performance in groups of different sizes. We investigated how
baseline levels of the steroid hormones, corticosterone and testosterone, were associated
with choice of colony size and the likelihood of moving to a different site in later years
in colonially nesting Cliff Swallows (Petrochelidon pyrrhonota) in southwestern Nebraska,
USA, in 2000–2004. We sampled hormone levels of birds caught at colonies and, using
mark–recapture, monitored their movement and choice of colony size …