Abstract
ABSTRACTArctic weather in spring is unpredictable and can also be extreme, so Arctic‐breeding birds must be flexible in their breeding to deal with such variability. Unpredictability in weather conditions will only intensify with climate change and this in turn could affect reproductive capability of migratory birds. Adjustments to coping strategies are therefore crucial, so here we examined the plasticity of the adrenocorticotropic stress response in two Arctic songbird species—the snow bunting (Plectrophenax nivalis) and Lapland longspur (Calcarius lapponicus)—breeding in northwest Greenland. Across the breeding season, the stress response was strongest at arrival and least robust during molt in male snow buntings. Snow bunting females had higher baseline but similar stress‐induced corticosterone levels compared to males. Modification of the stress response was not due to adrenal insensitivity, but likely regulated at the anterior pituitary gland. Compared to independent nestlings and adult snow buntings, parental‐dependent chicks had a more robust stress response. For Lapland longspurs, baseline corticosterone was highest at arrival in both male and females, and arriving males displayed a higher stress response compared to arriving females. Comparison of male corticosterone profiles collected at arrival in Greenland (76°N) and Alaska (67–71°N;) reveal that both species have higher stress responses at the more northern location. Flexibility in the stress response may be typical for birds nesting at the leading edges of their range and this ability will become more relevant as global climate change results in major shifts of breeding habitat and phenology for migratory birds. J. Exp. Zool. 323A: 266–275, 2015. © 2015 The Authors. J. Exp. Zool. published by Wiley Periodicals, Inc.
Highlights
This paper is dedicated to the memory of Bill Burnham, former Director of the Peregrine Fund
Snow buntings (Plectrophenax nivalis) and Lapland longspurs (Calcarius lapponicus) breeding early in the season in Alaska, appear to maintain a lower adrenocortical response to stress when compared to other Arctic breeding species such as white-crowned sparrows (Zonotrichia leucophrys) and American tree sparrows (Spizella arborea) that breed at lower latitudes in Alaska (Wingfield et al, '95; Romero et al, '97; Meddle et al, 2002; Holberton and Wingfield, 2003; Krause et al, 2015)
Capture and Sampling We captured male and female snow buntings and Lapland longspurs on their breeding grounds with mist nets, Potter traps baited with seeds, or clap nets at the nest, the latter triggered by a 5 m rope pulled by a hidden observer
Summary
This paper is dedicated to the memory of Bill Burnham, former Director of the Peregrine Fund. Studies of northern latitude migratory songbirds suggest that many species have a robust adrenocortical response to acute stress upon arrival onto their breeding grounds (Reneerkens et al, 2002; Holberton and Wingfield, 2003; Meddle et al, 2003; Wingfield and Ramenofsky, 2011; Krause et al, 2015). These hormonal patterns are evident in species in which males arrive first (Wingfield and Hunt, 2002). If environmental conditions deteriorate for prolonged periods, there is the potential for a robust adrenocortical response to stress (Astheimer et al, '95)
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