Acta Ornithologica, vol. 34, no. 2

The level of maximum food energy or maximal existence metabolism (MPE) is 1.3 times higher in passerines than in non-passerines, which agrees with the ratio of their basal metabolic rates (BMR). The optimal ambient temperature for maximizing productive processes (e.g. reproduction, moult) is lower for passerines than for non-passerines, which allows passerines to have higher production rates at moderate ambient temperatures. This may explain variation in bioenergetic parameters along latitudinal gradients, such as the ecological rule of clutch size (or mass) increase in the northern passerine birds. The increased potential for productive energy output in the north may allows birds to moult faster there, as well. This phenomenon allows passerine birds to occupy habitats of widely fluctuating ambient temperatures in comparison with non-passerine birds of similar size. Passerines have more effective system for maintenance of heat balance at both high and low temperatures. The high metabolism and small body sizes in passerines are consistent with development of omnivory and ecological plasticity. Among large passerines the unfavourable ratio of MPE to BMR should decrease energy available for productive processes. This consequence limit both reproductive output and the development of long migration (especially in Corvus corax).

Bibliogr. p. 171

S. [165]-172 : il. ; 27 cm

Streszcz. pol.

P. [165]-172 : ill. ; 27 cm

Referat wygłoszony na Second Meeting of the European Ornithologists' Union

Abstract in Polish

Bibliogr. s. 171