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Full-Text Articles in Animal Sciences
Fluctuating Survival Selection Explains Variation In Avian Group Size, Charles R. Brown, Mary Bomberger Brown, Erin A. Roche, Valerie A. O'Brien, Catherine E. Page
Fluctuating Survival Selection Explains Variation In Avian Group Size, Charles R. Brown, Mary Bomberger Brown, Erin A. Roche, Valerie A. O'Brien, Catherine E. Page
School of Natural Resources: Faculty Publications
Most animal groups vary extensively in size. Because individuals in certain sizes of groups often have higher apparent fitness than those in other groups, why wide group size variation persists in most populations remains unexplained. We used a 30-y mark– recapture study of colonially breeding cliff swallows (Petrochelidon pyrrhonota) to show that the survival advantages of different colony sizes fluctuated among years. Colony size was under both stabilizing and directional selection in different years, and reversals in the sign of directional selection regularly occurred. Directional selection was predicted in part by drought conditions: birds in larger colonies tended …