Comparative Biochemistry and Physiology Part A 127 (2000) 309 – 329 The influence of body mass, climate, and distribution on the energetics of South Pacific pigeons Brian K. McNab * Department of Zoology, Uniersity of Florida, Gainesille, FL 32611, USA Received 24 January 2000; received in revised form 15 August 2000; accepted 17 August 2000 Abstract Rate of metabolism and temperature regulation were studied in 16 species of South Pacific pigeons, which constitute 13 fruit-eaters, 1 seed-eater, 1 fruit/nut-eater, and 1 fruit/leaf-eater; 14 tropical and two temperate species; and ten mainland and six intermediate- or small-island species. The data presented here and those from 11 additional columbids indicate in an analysis of covariance that log 10 basal rate of metabolism is correlated with log 10 body mass (P 0.0001), distribution (P =0.0023), and climate (P =0.0016). These factors account for 94.3% of the variation in log 10 basal rate of metabolism. In this analysis the lowest basal rates, corrected for body mass, are found in tropical pigeons living on small oceanic islands, whereas the highest basal rates are found in temperate species living on continents. The reduction of basal rate in large columbids facilitates their long-term persistence on small islands characterized by a limited resource base and unstable weather. Some small-island specialists have a smaller mass than their continental relatives, which further reduces resource requirements. The question whether a reduction in basal rate occurs in small columbids on small islands is unresolved. Log 10 minimal thermal conductance is apparently correlated only with log 10 body mass (P 0.0001); r 2 =89.4%. The mean nocturnal body temperature of columbids is 39.7°C. © 2000 Elsevier Science Inc. All rights reserved. Keywords: Body mass; Climate; Energetics; Island size; Pigeons www.elsevier.com/locate/cbpa 1. Introduction Only a small fraction of the taxonomic and ecological diversity of birds has been incorporated into the study of avian energetics. Much of this diversity is found in the tropics, whereas most studies of avian energetics have concerned small, seed-eating, temperate passerines or polar seabirds. Few species that belong to families that are restricted to the lowland tropics, or that are tropical representatives of families that have a climatically broad distribution, have been studied. Nevertheless, previous studies have suggested that basal rate in birds is correlated with body mass (Lasiewski and Dawson, 1967; Aschoff and Pohl, 1970; Reynolds and Lee, 1996), taxonomy (Lasiewski and Dawson, 1967; Aschoff and Pohl, 1970), food habits (McNab, 1988, 1994b; McNab and Bonaccorso, 1995), foraging style (McNab and Bonaccorso, 1995), climate (Weathers, 1979), plumage colour at low latitudes (Ellis, 1980), body composition (McNab, 1994a), and (for insular species) island size (McNab, 1994b). A widespread, diverse family is the Columbidae (pigeons and doves), order Columbiformes. Columbids are found from cold-temperate to * Corresponding author. Tel.: +1-352-3921178; fax: 1-352- 3923704. E-mail address: mcnab@zoo.ufl.edu (B.K. McNab). 1095-6433/00/$ - see front matter © 2000 Elsevier Science Inc. All rights reserved. PII:S1095-6433(00)00268-3