Habitat, Dominance, and the Phenotypic Quality of Male Black-Capped Chickadees

Abstract

AbstractAbstractThe provisioning of offspring is limited by resource abundance and is therefore likely to vary with habitat quality and the ability of parents to obtain food. Provisioning effort may also vary because males choose different life-history strategies depending on their rank and environment. Socially dominant males have higher costs of self-maintenance compared with subordinates, yet this is likely compensated for by their priority access to resources. It is unclear, however, whether this translates into benefits for females through male provisioning effort, and how this might vary with habitat suitability. We assessed patterns of body condition, blood hematocrit levels, and provisioning effort of dominant and subordinate male Black-capped Chickadees (Poecile atricapillus) breeding in two habitats known to differ in quality. Within ranks, males were similar in size and condition across habitats. Dominant males were not structurally larger than subordinates, but they were in better condition than subordinates in both habitats. There was an additive effect of habitat and dominance rank on hematocrit level; dominant males had higher hematocrit levels than subordinates regardless of habitat, and all males breeding in poor habitat had elevated hematocrits. A habitat-rank interaction revealed a greater disparity in provisioning rates among dominant and subordinate males in poor habitats. These results suggest that dominant males may be particularly good mates when resources are scarce.