Gouldian finch metabolic data for Buttemer et al. 2021 jeb242577

Evidence from a number of species suggests behaviours associated with
social rank are positively correlated with metabolic rate. These studies,
however, are based on metabolic measurements of isolated individuals,
thereby ignoring potential effects of social interactions on metabolic
rates. Here, we characterised three pertinent metabolic indices in the two
predominant genetic colour morphs of the Gouldian finch (Erythrura
gouldiae): diurnal resting metabolic rate (RMR), nocturnal basal metabolic
rate (BMR), and exercise-induced maximal metabolic rate (MMR). Research
reveals red-headed morphs consistently dominate the less aggressive
black-headed morphs and the two morphs to differ in other behavioural and
physiological traits. We measured daytime RMR of intermorph naïve birds
(first-year virgin males maintained in total isolation from opposite
colour morphs) and their metabolic responses to viewing a socially
unfamiliar bird of each colour. Subsequently, each bird was placed in a
home cage with an opposite colour morph (intermorph exposed) and the
series of measurements repeated. Daytime RMR was indistinguishable between
the two morphs, whether intermorph naïve or intermorph exposed. However,
both red- and black-headed birds showed a greater short-term increase in
metabolic rate when viewing an unfamiliar red-headed bird than when seeing
a black-headed bird, but only when intermorph naïve. Measurements of BMR
and exercise-induced MMR did not differ between the two morphs, and
consequently aerobic scope was indistinguishable between them. We propose
that the suite of behavioural differences between these two sympatric
morphs are functionally complementary and represent evolutionary stable
strategies permitting establishment of dominance status in the absence of
metabolic costs.