Meeting Abstract

P1.128  Saturday, Jan. 4 15:30  Feather CORT predicts subsequent year’s lay date in female Tree Swallows BERK, SA*; ROMERO, LM; PARKER, C; ARDIA, DR; WINKLER, DW; ROSS, C; GILL, CJ; University of Montana; Tufts University; Tufts University; Franklin & Marshall College; Cornell University; Hampshire College; Hampshire College sara.berk@umconnect.umt.edu

Feather growth takes place over a relatively short time period, but has numerous consequences for future reproduction. Birds with lower quality feathers may face costs during the non-breeding season through decreased flight efficiency or thermoregulation. Furthermore, feathers function as a social signal and have been demonstrated to impact territory quality and mate choice. Prior laboratory work has found that elevated corticosterone (CORT) during feather growth decreases feather quality, which may affect both migratory efficiency and reproductive success over the subsequent year. I used a new methanol extraction technique to investigate the relationships between CORT deposited in feathers (molted at the end of the prior breeding season) and current reproductive effort using a population of Tree Swallows () Tachycineta bicolor () breeding at Beaverhill Lake, Alberta. I found that females with higher feather CORT had later clutch initiation dates. This relationship could reflect 1. delayed spring migration due to low feather quality, 2. delayed lay due to greater challenge in the prior year, or 3. simply that lower quality individuals have higher CORT and lay later in the season. Measurement of CORT in feathers is relatively recent in the literature, and is used to estimate general CORT levels over the entire growth of the feather. Feather CORT also allows examination of CORT levels experienced by the animal many months prior, without the need for recapturing individuals at separate time points. This data indicates the utility of such an approach for understanding long-term implications of CORT elevation on birds.