Student Scholars Day

Factors That Affect Nestling Growth Rates in Tree Swallows

Henry Hall Atrium 26

Tree swallows are common aerial insectivores. Nestlings are fed until they fledge 20 days after hatching. From 2008-2012, we examined the effects of brood size and year on nestling growth (head-bill length, mass and wing length) from 430 nestlings in 102 broods when 3, 6, 9 and 12 days old. We measured nestlings at ND12 because nestling size at ND12 predicts size at fledging. Brood sizes ranged from 1-7 nestlings. Head-bill, mass and wing growth rates were all significantly affected by brood size and year. In the most common brood sizes of 4, 5, and 6, head-bill and wing growth rates were significantly affected by brood size, mass was not. Nestling size at ND3 was positively correlated with size at ND12. On ND12, head-bill length, mass and wing length were positively correlated with each other suggesting that brood size affects nestling growth. Nestlings in BS 4-6 were the largest on ND12. Nestling growth rates changed with year suggesting that food availability affects growth.