Modulating the Corticosterone Stress Response: A Mechanism for Balancing Individual Risk and Reproductive Success in Arctic-Breeding Sparrows?

• Published in: The Auk
• Main Authors: Holberton, Rebecca L., Wingfield, John C.
• Other Authors: Brittingham, M.
• Format: Article in Journal/Newspaper
• Language: English
• Published: Oxford University Press (OUP) 2003
• Subjects: Animal Science and Zoology; Ecology, Evolution, Behavior and Systematics; Arctic; Alaska
• Online Access: http://dx.doi.org/10.1093/auk/120.4.1140; http://academic.oup.com/auk/article-pdf/120/4/1140/29687547/auk1140.pdf

Abstract Modulation of the adrenocortical stress response with respect to the degree of parental activity was investigated in three Arctic-breeding species of songbirds faced with limited opportunities to breed. The hypothesis that the strength of the response can be lowered when reproductive effort or investment is greatest was tested by measuring the adrenocortical response to handling stress during two breeding stages that represented different levels of reproductive effort (i.e. before young were present [preparental] and while feeding nestlings [parental]). Comparisons of the corticosterone stress response (baseline at capture and subsequent samples 5, 10, 30, and 60 min after capture) were made within and between both sexes of American Tree Sparrows (Spizella arborea), White-crowned Sparrows (Zonotrichia leucophrys gambelii), and Savannah Sparrows (Passerculus sandwichensis) breeding above the Arctic Circle at Toolik Lake, Alaska. In general, body mass and baseline corticosterone did not differ between sexes within each of the three species, nor did they change during the two stages of breeding (tree and White-crowned sparrows only). In all three species, males had stronger adrenocortical responses than females during the preparental period, a time when males may expend less in reproductive effort than females. However, during the parental stage (tree and White-crowned sparrows only), the stress response of males declined and became similar to that of females because both sexes fed young. Females of both species (having considerable reproductive effort throughout both stages via egg laying or incubation and feeding young) showed no change in stress response with breeding stage. These results support the hypothesis that individuals with limited opportunities to breed can modulate the adrenocortical stress response when reproductive effort or investment is greatest as a way to maximize breeding success.