For example, a black eagle mother lays two eggs, and the first-hatched chick pecks the younger one to death within the first few days. In the blue-footed booby, there is always the emergence of a brood hierarchy. The dominant chick will attack the subordinate one in times of food scarcity, often pecking it repeatedly or driving it from the nest.[14] Among spotted hyenas, sibling competition begins as soon as the second pup is born, and 25% of pups are killed by their siblings.[15] (see: Siblicide)