A quantitative analysis of the behaviour of the Chinstrap penguin Pygoscelis antarctica and Macaroni penguin Eudyptes chrysolophus on Bouvetoya during the late incubation and early nestling periods
AbstractThe division of labour between the sexes, and their respective behaviour, were studied by means of timelapse photography during the incubation and brooding periods. Chinstrap penguin. Both mates were equally attentive in incubating the eggs and brooding the small chicks. During late incubation the mean duration of a shift was 35 h. This decreased to 14-1.5 h during the initial nestling period. Most reliefs took place around noon or in the evening/night, indicating a basic brooding shift of 12 h. During the incubation and hatching periods the mate was absent (presumably at 5ea) for 29 h at a time. on average. The mean duration of absence decreased to 12-13 h during the early nestling stagc. indicating that the adults had been feeding in nearby waters. Six adults with stomach contents had fed exclusively on krill Euphausia superba. During the incubation period the proportion of time spent prone averaged 92% of the total time spent on the nest. for both sexes, but. during the hatching and initial nestling periods. this decreased rapidly in relation to the time spent upright, probably because progressively less heat transfer from the brood patch was required. Macaroni penguin. In the ten days just before the eggs were hatched the males at four nests were responsible for 82-100% of total incubation. Presence or absence of the females at the nests during this stage varicd greatly. At one nest the female was not observed at all. At another she stayed by the nest during the entire survey period, but relieved the incubating male for only 5% of the time. During incubation the males adopted an upright posture far more often than the females, but even the latter incubated significantly more frequently upright than the Chinstrap penguin. This specific difference may be related to the fact that the Macaroni penguins had only a single egg. whereas the Chinstraps had two. The prone posture better enables the nest contents to be properly covered. Both species. During incubation, both the male and female birds assumed a resting or sleeping posture for more than 90% of their time on the nest. Egg-shifting, rotation on the nest. and preening together accounted for about 2-3% of their time. Time spent in agonistic and territorial behaviour. unusually aroused by the presence of other penguins passing by, accounted for 0 . 9 1 of the time in the Chinstrap, but for only 0.1% in the Macaroni penguin. Ecstatic displays were sporadically observed in the Chinstrap by both sexes. Mean egg temperature during incubation. measured close to the top of the egg. was 37.4°C for both species.
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