Chinstrap penguins,Pygoscelis antarctica, after being relieved from incubation, collect stones from the ground or steal them from other nests and incorporate them into their own nests. The variation in stone-collecting behaviour after incubation reliefs, nest defence intensity and nest weights were measured in a sample of 100 nests in a large subcolony sited in the Vapour Col Chinstrap penguin colony on Deception Island, South Shetland Islands. Males collected more and larger stones, stole more stones and were more aggressive in nest defence towards potential thieves than females. Females suffered stone theft to a greater degree than males. Nests changed in weight during a period of 20 days. Initial nest size was negatively correlated with change in nest weight. The intensity of stone collection and theft by males was positively correlated with the increase in nest weight and with the final nest weight attained, while nest defence intensity by males and females was positively correlated with initial and final nest weight. Flooding after a snow storm affected 31 of nests and caused the loss of up to 14 of eggs/hatchlings. Flooded nests were significantly smaller than non-flooded nests. Results indicate that nest maintenance behaviour and stone theft in Chinstrap penguins serve to improve nest quality and thus enhance reproductive success.
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