INCUBATION DEVELOPMENT AND ASYNCHRONOUS HATCHING IN JUNGLEFOWL

In gallinaceous birds and other nidifugous species, it is thought that effective incubation does not start before the last egg is laid, and young hatch synchronously (LACK, 1968). We investigated the egg-laying and nest-attendance pattern of the precocial nidifugous red Burmese J unglefowl Gallus gallus spadiceus, and its consequences for the asynch rony of embryo development and of hatching. Eggs were laid in sequence s, followed by pause days. Egg-weight in these sequences decreased by 0.6 g/egg. When laying, females sat in the nest for 1-3 h/day, and att ended the nest overnight on days on which the last eggs of a clutch we re laid. At the moment the last egg was laid, first eggs were already attended for 40 h (range 16-84 h), which resulted in extreme developme ntal asynchrony at the end of laying (measured as the diameter of the area vasculosa). Last eggs of clutches decreased markedly in weight (b y more than 1 g/egg) and had shorter incubation times than the heavier first eggs. Eggs hatched asynchronously over a period of 15 h (range 7-33 h) and in the order of laying. The development of incubation beha viour, asynchrony of embryo development and of hatching of the precoci al nidifugous Junglefowl, corresponded to a high degree to what is kno wn of altricial species.