QUALITATIVE COURSE OF EMBRYONIC O-2 CONSUMPTION IN ALTRICIAL AND PRECOCIAL BIRDS

The course of embryonic V-O2 was examined in 24 altricial and 27 preco cial bird species to test differences in its phenology. Some authors s uggest that altricial species lack a plateau in V-O2-development found in precocial species. Based on the recently available data we find th e following: All species (except members of the family Megapodiidae) e xhibit a plateau. Their V-O2-development follows an identical basic co urse which can be described by an exponential increase interrupted by the plateau. There seems to be no fundamental difference between altri cials and precocials with respect to the general presence of a plateau . In small altricials the plateau lasts only a few hours. It can be ov erlooked easily when the measurement is not continuous or when many in dividual measurements are averaged. However, the plateau-V-O2 is lower (about 35%) and shorter (12.4% of incubation time; 16.9% in precocial s) in the altricials. Total energy consumption during incubation is 1. 9 kJ/g in altricial and 2.2 kJ/g in precocial species.