Colonial breeding is common in seabirds, and may provide individuals with benefits such as increased protection from predators by joint defence, improved information exchange and enhanced access to mates. However, the presence of large numbers of individuals in breeding colonies may also lead to interference, especially where conspecific behaviour disrupts the normal chick-rearing routine. Using standardised video recordings, we describe and quantify for the first time such disruptive behaviour by conspecifics in penguins. This disruptive behaviour appeared to be common in chick-feeding Southern rockhopper penguins Eudyptes chrysocome and its occurrence did not differ significantly among the colony areas where observations were made. Females were commonly (77 % of 111 observation sessions) disrupted by other adults when attempting to feed chicks alone during the crSche stage. They consequently reduced the time spent with their chicks. Disrupted chicks compensated by begging more intensely when their female parents were present, and they did not eat significantly less often than undisrupted chicks. In contrast, disruptive behaviour towards chick-feeding males or pairs was never observed. This study supplements knowledge about a disruptive behaviour that appears to be common but for which the function remains unclear in penguins, as the intruders did not appear to gain any visible benefits.
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