The Blue-footed Booby (Sula nebouxii) is a bird in the Sulidae family, which includes ten species of long-winged seabirds. It is of the species Sula, which comprises six boobies. It is easily recognizable by its distinctive bright blue feet, which is a sexually selected trait. Males display their feet in an elaborate mating ritual by lifting one and then the other up, while strutting before the female. Both males and females prefer mates with brighter feet and adjust their parental investment based on the attractiveness of their mate.
The natural breeding habitat of the Blue-footed Booby is tropical and subtropical islands of the Pacific Ocean. Their range extends from the Gulf of California down along the western coasts of Central and South America to Peru. About half of all breeding pairs nest on the Galápagos Islands.
The Blue-footed Booby usually lays one to three eggs at a time. The species practices asynchronous hatching, which means that eggs that are laid first are hatched before the consequent eggs, resulting in a growth inequality and size disparity between siblings. This could result in facultative siblicide in times of food scarcity. Therefore, the species is an effective model for studying parent-offspring conflict and sibling rivalry.