Ontogeny of the adrenocortical response in an extremely altricial bird
Document Type
Article
Publication Date
9-23-2019
Abstract
Life history theory predicts that physiological and behavioral responsiveness to stress should be delayed in development until the benefits of heightened reactivity outweigh the costs of potentially chronic glucocorticoid levels. Birds often acquire stress-responsiveness at locomotor independence, however, both stress-responsiveness and locomotor ability are delayed in birds with altricial developmental strategies. Parrots (Psittacidae) are extremely altricial, but it is not known whether they also postpone physiological responsiveness to stress until locomotor independence. We quantified individual variation in baseline and stress-induced plasma corticosterone (CORT) concentrations, the main avian glucocorticoid, in wild green-rumped parrotlets (Forpus passerinus) of Venezuela at four stages of nestling development. Parrotlet neonates are very underdeveloped and compete for parental care among extreme sibling size hierarchies, a competitive scenario that might benefit from early hypothalamic–pituitary–adrenal (HPA) functionality. Nestlings that underwent a standardized restraint stress-treatment showed higher average CORT concentrations compared to baseline in all age groups sampled, and exhibited no evidence of age-related changes in the stress response. This is 2 weeks before locomotor independence and earlier than previously documented for altricial species. Results suggest that precocity of HPA function may be advantageous to growth and survivorship in extremely altricial birds.
Recommended Citation
Berg, KS, Delgado, S, Mata-Betancourt, A, Krause, JS, Wingfield, JC, Beissinger, SR. Ontogeny of the adrenocortical response in an extremely altricial bird. J Exp Zool. 2019; 331: 521– 529. https://doi.org/10.1002/jez.2317
Publication Title
J Exp Zool
DOI
10.1002/jez.2317
Comments
© 2019 Wiley Periodicals, Inc.
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