Meeting Abstract
103.2 Tuesday, Jan. 7 08:30 Experimental relationships between plasma- and feather-levels of corticosterone in a free-living bird FAIRHURST, G.D.*; MARCHANT, T.A.; SOOS, C.; MACHIN, K.L.; CLARK, R.G.; Univ. of Saskatchewan | Environment Canada, Saskatoon; Univ. of Saskatchewan, Saskatoon; Environment Canada | Univ. of Saskatchewan, Saskatoon; Univ. of Saskatchewan, Saskatoon; Environment Canada | Univ. of Saskatchewan, Saskatoon graham.fairhurst@usask.ca
Integrated measures of corticosterone (CORT), such as from feathers (CORTf), have intuitive appeal because they incorporate the duration, as well as the amplitude, of glucocorticoid secretion. However, CORTf is a fundamentally different measure of physiology than an instantaneous sample of CORT from plasma, so it is unclear as to when and if these measures should be correlated. We hypothesized that CORTf should correlate with instantaneous measurements of plasma CORT when the latter reflect sustained changes in the activity of the hypothalamic-pituitary-adrenal axis. To test this, we experimentally manipulated levels of plasma CORT in wild nestling tree swallows (Tachycineta bicolor) using 5-day time-release CORT pellets, and measured plasma CORT and before, during, and at the end of hormone manipulation (days 7, 9, and 11 post-hatch, respectively). CORTf and plasma CORT were significantly positively related only when the latter was at its highest and most variable (day 9). Our results demonstrate that CORTf from free-living birds reflects plasma CORT, but correlations may not always be expected, especially if elevations in plasma CORT are relatively modest and of short duration. Future studies aiming to better understand CORTf from nestlings will benefit from manipulating the nest environment.
