A Quantitative Analysis of the Incubation Behavior of Adelie Penguins

Publication Type:
 Journal Article
Year of Publication:
 1977
Authors:
 Dirk V. Derksen
Publication/Journal:
 The Auk
Keywords:
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Abstract:

The incubation period of the Adelie Penguin was studied quantitatively to determine the behavioral requirements for successful reproduction. Incubation was divided into early, middle, and late periods to facilitate comparison between sexes and to evaluate activity in relation to stages of incubation.
Analysis of time-lapse photo sequences showed that prone postures accounted for 87 to 95% of the nest time from clutch completion to hatching. Upright postures were most often comfort movements and were more frequent during the prelaying, laying, and late (hatching) periods than in early and middle incubation.
Intensity of incubation was measured by the time an incubating bird spent in prone and upright positions. Prone postures were considered more intense. Intensity increased rapidly following clutch completion. Attentive periods increased in duration and decreased in number per day as the laying phase was completed. Incubation intensity remained stable from clutch completion to hatching. An increase in upright restless activity during hatching probably was a result of chick feeding and vocalization and response to the movement on noninrubating birds passing the nest. No statistical difference in incubation intensity between sexes was found.
A diurnal rhythm of upright restless movements during incubation was shown. There was considerable variation in restlessness from day to day and between individuals, but when all birds were grouped, a cycle of activity emerged. Peak restless activity occurred at 1100 G.M.T. Two external factors, ambient air temperature and light intensity, were compared with upright restless-
ness. Light intensity and activity showed nearly identical cycles. Ambient air temperature showed no obvious relationship to restlessness. Social activity may influence restlessness during incubation.
Egg temperatures were measured to determine incubation postures functional to heat maintenance and also to learn of changes during incubation. Collation of incubation events observed from a blind and recorded egg temperatures showed that eggs chilled rapidly when birds stood upright. A buildup in egg temperature from incubation day 12 to a maximum on day 21 occurred. A general trend of decreased upright restless movement corresponded to the buildup in egg temperatures and is probably responsible for it. Higher, more stable egg temperatures were shown for the middle period of incubation. Toward hatching egg temperatures fluctuated, but they did not drop drastically until after hatching.

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