| By human standards, relations between adult herring gulls and chicks are somewhat confused. Like some other large gulls, the herring gull, Larus argentatus, often steals chicks from other nests in its colony, killing and eating them or feeding them to its own young. However, it may also try to raise the stolen chicks by mistake. A herring gull chick, for its part, is just as easily confused. When its parent returns to the nest, a chick pecks at the red dot on the end of the large beak to obtain the food it may or may not carry. Yet it will just as eagerly peck at the red eraser on the end of a pencil. Behaviorists call this kind of instinctive, blind response a fixed action pattern and its trigger (the red dot) a sign stimulus, or releaser. |
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