One of the three nestlings has grasped the adult's bill in order to induce the adult to feed it by regurgitation. Birds of North America Online reports that at first after nestlings hatch, parents reguritate fish "boluses" (balls) onto the floor of the nest, where the young birds feed on them. One study found that thereafter "older siblings began to intercept boluses directly from the parents’ bills. By day 16, direct feeding predominated and older chicks rapidly became superior in obtaining food, compared to junior siblings."