The ecological energetics of birds in New Guinea

Abstract

The energetics of 79 species of birds living in greater New Guinea, data for 44 of which are presented here for the first time, is examined to determine the extent to which it reflects the behavior of species and the conditions they encounter in the environment. Body mass alone accounts for 86.6% of the variation in the basal rate of metabolism of these species, whereas the combination of body mass, foraging sub- strate, flightless condition, activity, and life on islands or continents collectively account for 95.2% of its variation. When the passerine/non-passerine dichotomy is added to the analysis, the six factors account for 96.7% of the variation in basal rate. Basal rate also correlates with other factors, including maximal altitude of distribution, torpor, and food habits when individually combined with body mass, but they lose significance when other factors are brought into the analysis. Altitudinal limits to distribution can be included in the analysis only if activity is dropped because of the correlation between these factors. Torpor correlates with an aerial feeding strategy. Food habits correlated with activity level and the passerine/non-passerine dichotomy. The attempt to account for the variation in the energetics of birds by a phylogenetic analysis is inappropriate because the fundamental basis of energetics is physiological with strong behavioral and ecological overtones. Body mass accounts for 90.4% of the variation in thermal conductance. The regulated level of body temperature varies from ca. 39 to 41°C at masses > 100 g, below which it decreases to 37 and 39°C at 10 g, with a few small species having body temperatures as low as 35°C. New Guinea is an important source for the terrestrial avifauna of South Pacific islands. The characteristics of its birds therefore are appropriate standards by which to judge the adjustments occurring in, and required of, birds endemic to these islands.