Double logarithmic relationships between BMR and body mass for 21 avian herbivores
from the literature (black circles) together with data obtained for the Rufous-tailed Plantcutter
(Phytotoma rara ; black triangle). The line represents the regression obtained with these
values, with the equation: BMR = 4.95 mb -0.286 (Rezende et al. 2001).
Log10 mass-specific basal rate of metabolism as a function of log10 body mass in a barbet, toucans, a hornbill,
fruit pigeons (including Ducula pacifica ), and flying foxes (pteropodids; Dobsonia moluccensis
& Pteropus vampyrus ). Also shown are the standard curves for nonpasserines (Aschoff and Pohl 1970 ),
all birds (Reynolds and Lee 1996 ), and all mammals (Figure from: McNab 2001 ).
As with metabolic rates, birds tend to have higher body temperatures than mammals. In general, body temperatures of birds range from about 38 - 42 degrees C. Body temperatures of large flightless birds
(e.g. ostrich & emu) and some aquatic birds (e.g. penguins) are on the lower end of this range (& within the range of mammals).
Relationship between metabolic rate & size, food habits, & altitude -- McNab (2003) reported that 99% of the variation in metabolic rate among different species of birds of paradise (N = 13) was based on three factors: body weight, food habits and the altitude at which the birds live. New Guinea is home to most birds of paradise. The birds get their name from the unique circumstances surrounding their discovery by Europeans in the 1500s. When the first preserved specimens reached Spain, their feet had been removed. The oddity of these seemingly footless birds, combined with their unique colors and shapes, prompted the Spanish to conclude they spent their whole lives aloft - in the metaphorical paradise of the sky - without ever alighting on Earth.