One potential proximate cause of the timing of the nest relief cycle of adelie penguins was investigated by testing the hypothesis that the females count the days that they are gone from the nest so they can return to relieve the fasting male before he abandons the nest. Females were prevented from going to sea, after they finished laying their eggs and had left their nest, for 4 days (the average delay caused by laying a third egg in the first experiment) and the duration of the foraging trip was determined.
Davis, L.S. and G.D. Miller. 1990. Foraging patterns of Adélie Penguins during the incubation period. In Knowles & Kerry (Eds.). Antarctic ecosystems: change and conservation. Springer Verlag, Berlin. pp203-207.
Miller, G.D. And Davis, L.S. 1993. Foraging flexibility of Adelie penguins (Pygoscelis adeliae): Consequences for an indicator species. Biological Conservation 63: 223-230.
Davis, L.S. Ward, G.D. Sadlier, R.M.F.S. Foraging for Adélie penguins during the incubation period. Notornis 35(1): 15-23, 1988.