Egg size, incubation periods and hatching success of Little Penguins,Eudyptula minor

The size of eggs, laying intervals, incubation periods, hatching success and causes of egg mortality in Little Penguins, Eudyptula minor, were studied on Phillip Island, Victoria. The mean laying interval was 3 days (range 2–7 days); the mean incubation period was 35.4 days (range 33–44 days). Second-laid eggs were shorter and broader than first-laid eggs without any difference in weight, volume or hatching success. Single-egg clutches had a much lower success than two-egg clutches. Hatching success varied from 47% to 87% (mean 67%) between 1968–69 and 1998–99 and the main cause of egg mortality was desertion. It is suggested that annual fluctuations in hatching success may be linked to annual variations in food availability through the failure of some birds to relieve their partners before they are forced to desert the eggs.