Ecology of Feather Corticosterone:
The natural world is dynamic and full of unpredictable environmental challenges (food deprivation, bad weather, predation, etc.). Vertebrates possess a physiological mechanism called the hypothalamic-pituitary-adrenal (HPA) axis that orchestrates physiological and behavioral changes that help them cope with these challenges. The HPA axis is fascinating because on the one hand it responds adaptively to help the animal overcome the challenge, yet continued stimulation of the same system can lead to numerous adverse physiological and behavioral effects.
When the HPA axis is activated it releases hormones called glucocorticoids (GCs). For decades, researchers have quantified GCs in the blood, which provides a short-term measure. An alternative technique of extracting corticosterone (CORT; the primary avian GC) from feathers is being increasingly used because it provides a different, longer-term perspective on CORT physiology. I did my Ph.D. in the Bortolotti-Marchant lab at the University of Saskatchewan where this technique was developed.
For over 10 years, I have been exploring and applying feather CORT in a variety of systems to better understand of the ecophysiology of stress in birds. Below are a few key examples of the collaborative projects that have contributed to our understanding of feather CORT and highlight the strength and flexibility of this technique.
Additional papers using feather CORT can be found on my publications page. If you plan on using feather CORT, you may find it useful to read my guide for preparing feather samples.
Validating plasma-feather relationships
By manipulating CORT in nesting Tree Swallows (Tachycineta bicolor), this study with colleagues at Environment Canada (Bob Clark and Catherine Soos) and the University of Saskatchewan (Karen Machin and Tracy Marchant) demonstrates that the CORT in feathers comes from general circulation. This work also provides an understanding of the differences between feather- and plasma-based measures of CORT physiology and explains why they can—but won’t always—be correlated.
Fairhurst, G. D., T. A. Marchant, C. Soos, K. L. Machin, and R. G. Clark. 2013 Experimental relationships between plasma- and feather-levels of corticosterone in a free-living bird. Journal of Experimental Biology 216(21):4071-4081. [PDF download]
Responses to small-scale environmental change
In collaboration with Debbie Kelly, we showed that short- and long-term cage enrichment elicited different physiological responses in captive Clark’s nutcrackers (Nucifraga columbiana), with the former acting as a stressor and birds exhibiting acclimation to the latter. Moreover, this work showed that the CORT from sections of feathers reflected environmental conditions during the period that each section was grown.
Fairhurst, G. D., M. D. Frey, J. F. Reichert, I. Szelest, D. M. Kelly, and G. R. Bortolotti. 2011. Does environmental enrichment reduce stress? An integrated measure of corticosterone from feathers provides a novel perspective. PLoS ONE 6(3):e17663. [PDF download]
Consequences of sex-specific parental investment
This work, conducted in collaboration with Joan Navarro and Jacob González-Solís, showed that Cory’s shearwater (Calonectris diomedea) chicks are physiologically sensitive to parental provisioning, but in a sex-specific way, because male-biased investment was particularly influential to chick feather CORT. Our results also suggest that shearwater chicks may have suppressed their CORT secretion as an adaptive response to extended nutritional deficits.
Fairhurst, G. D., J. Navarro, J. González-Solís, T. A. Marchant, and G. R. Bortolotti. 2011. Feather corticosterone of a nestling seabird reveals consequences of sex-specific parental investment. Proceedings of the Royal Society B: Biological Sciences 279(1726):177-184. [PDF download]
In collaboration with Matthias Vögeli, Jose L. Tella, and David Serrano, we demonstrated a significant spatial structure to feather CORT values in the threatened Dupont’s Lark (Chersophilus duponti) that was unrelated to traditional measures of habitat (e.g., patch size, level of fragmentation). Moreover, by correlating feather CORT with feather-based measures of stable isotopes of carbon, we highlight the importance of considering the resources actually used by animals.
Fairhurst, G. D., M. Vögeli, D. Serrano, A. Delgado, J. L. Tella, and G. R. Bortolotti. 2013. Can synchronizing feather-based measures of corticosterone and stable isotopes help us better understand habitat-physiology relationships? Oecologia 173(3):731-743. [PDF download]