The Florida Scrub-Jay (Aphelocoma coerulescens) is a cooperative-breeding species endemic to Florida. It is currently listed as threatened and continues to decline throughout its range, largely as a result of habitat loss and degradation. A previous study demonstrated that daily energy expenditure (DEE) as a multiple of basal metabolic rate (BMR) in this species is increased greatly among males during the breeding season in an urbanized site. However, whether BMR itself varies between urbanized and wildland habitats needs to be established. We measured BMR in Florida Scrub-Jays over several years and seasons in both habitats to better understand the possible effect of urbanization on their energetics. We developed a thermoregulatory profile for the species, determining both BMR and thermal conductance. BMR did not vary between the 2 habitats, even when restricting the dataset to a single year and season to remove confounding variables. As expected, circadian period affected BMR, with mean nighttime (ρ) measurements (1.726 mL O2/g·h) lower than mean daytime (α) measurements (2.016 mL O2/g·h). Mean BMR for the daytime and nighttime was 1.871 mL O2/g·h, which is close to that expected for a passerine bird of 68.9 g mean mass. Daytime thermal conductance (C) was 14.5–18.6% higher than expected and the lower end (Tl) of the thermal neutral zone (TNZ) was 24 °C; we chose not to measure the upper limit of TNZ in this threatened species, but TNZ does extend at least to 36 °C. Florida Scrub-Jays appear to be adapted to the warm climate in which they are found. Despite previous research demonstrating that anthropogenic habitat modification results in increased DEE in Florida Scrub-Jays, it does not appear to have an effect on BMR. We note that a case cannot currently be made for urbanization affecting BMR in passerines.

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