Diurnal activity in the Adelie penguin(Pygoscelis adeliae)at Cape Royds, Antarctica

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Abstract
Hourly observations on six days during the 1965–66 breeding season are presented, graphically, and analysed. Although there was distinct diurnal change in temperature and light intensity the changes in the numbers of adults, pairs of adults, comfort movements, birds upright asleep, ecstatic displays, birds building and birds entering and leaving the rookery in the 10 min observational periods were not so rhythmical. Some evidence of diurnal variation in numbers, with mid-day minimum, appeared in January. It is suggested that this is due to the necessity for breeding birds to bring food to their chicks at regular intervals; earlier in the season when the demands of the chicks do not have to be met behaviour is governed largely by climatic expediency.