Nestling corticosterone response to microclimate in an altricial bird

Abstract

Although altricial young are dependent on their parents during early life, they must respond to environmental variation to maintain homeostasis. The hormone corticosterone (CORT) may be an important link between environment and phenotype during early life; however, no previous study has experimentally assessed the sensitivity of CORT to nest microclimate in altricial birds beginning to thermoregulate. We tested the hypothesis that microclimate influences CORT by cross-fostering nestling Tree Swallows (Tachycineta bicolor (Vieillot, 1808)) between thicker-walled “aspen” nest boxes and thinner-walled “plywood” nest boxes. Quantification of CORT in nestling feathers allowed us to consider hormone secreted over days, rather than instantaneously from blood samples. In agreement with our hypothesis, we detected significant positive relationships between feather CORT and increased temperature variability and maximum, but not minimum, nest box temperatures. This could reflect the energetic challenge of warmer temperatures or positive developmental effects on the nestling hypothalamic–pituitary–adrenal axis. Feather CORT was significantly lower in chicks hatched in aspen nest boxes compared with plywood ones, but cross-fostering did not influence nestling CORT. This suggests that the influence of natal nest box environment on feather CORT was likely greater than the influence of the foster nest box environment. The relationships we detected highlight the sensitivity of feather CORT to environmental variation and contribute insight into nestling responses to environmental change.

Habitat Quality Affects Early Physiology and Subsequent Neuromotor Development of Juvenile Black-Capped Chickadees

“…Feather CORT levels were determined by RIA as in previous studies [40]–[43], [34]. Measurements were performed on 100 µL of reconstituted methanol extracts that had been reconstituted in PBS and were duplicated.…”

Developmental stress: evidence for positive phenotypic and fitness effects in birds

“…Although developmental stress is a broad term, it generally refers to any sub-optimal condition experienced during either the prenatal or postnatal developmental period, including: food restriction, elevated glucocorticoid stress hormones, extreme ambient temperature, varied incubation temperature, immune challenges, psychological disturbances such as altered paternal care and social contact, and anthropogenic disturbances (e.g., Banerjee et al 2012;Buchanan et al 2003;Crino et al 2011;Fairhurst et al 2012;Grindstaff et al 2012;Honarmand et al 2010;Lynn and Kern 2014;Pravosudov and Kitaysky 2006;Spencer et al 2009;Walker et al 2005aWalker et al , 2005bWeaver et al 2004;Wilsterman 2015). The effects of developmental stress have been widely studied across taxonomic groups.…”

Experimental relationships between levels of corticosterone in plasma and feathers in a free-living bird

“…CORT was extracted from feathers using a methanol-based technique (see Bortolotti et al, 2008) that has been used previously with tree swallow nestlings (Harms et al, 2010;Fairhurst et al, 2012a). Feather length was measured, and the calamus cut, removed and discarded.…”

“…Work with birds has shown that feathers contain corticosterone (CORT) (Bortolotti et al, 2008;Koren et al, 2012), the primary avian GC. CORT in feathers (CORT f ) has been correlated with variation in parental provisioning (Fairhurst et al, 2012b), nest box microclimate (Fairhurst et al, 2012a), environmental enrichment (Fairhurst et al, 2011), expression of carotenoid-based signals (Bortolotti et al, 2009b;Mougeot et al, 2010;Kennedy et al, 2013), egg mass (Kouwenberg et al, 2013), stable isotopes of carbon (Fairhurst et al, 2013) and components of fitness (Bortolotti et al, 2008;Koren et al, 2012). This biomarker relates to diverse ecological factors, suggesting that it integrates CORT secretion in general, rather than expresses a response to any specific source of environmental variation.…”