The influence of body mass, climate, and distribution on the energetics of South Pacific pigeons

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< or =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< or =0.0001); r(2)=89.4%. The mean nocturnal body temperature of columbids is 39.7 degrees C.