How does the red spot on an adult herring gull’s bill guide a chick’s food-begging behavior?

The red spot on an adult herring gull’s bill serves as a key visual stimulus that guides a chick’s food-begging behavior. When an adult has food, it points its bill downward and waves it slowly in front of the chick, which triggers the chick to peck accurately at the red spot.1

This pecking response is considered a fixed action pattern, as it is performed automatically and correctly the first time it is elicited. By pecking at the spot, the chick induces the parent to regurgitate food for it to eat. While this behavior is initially innate, it is not strictly fixed; as the chick matures, its pecking accuracy improves, and after about two days, it requires the complete configuration of an adult’s head and bill—rather than just the spot alone—to elicit the response. Modern ethologists view this as a complex interaction between genetic predispositions and environmental experience rather than a purely innate or learned behavior.12