May 2, 2017 – Cook’s Petrel (Pterodroma cookii)
One of the smallest petrel species, these birds breed only on New Zealand’s Little Barrier, Great Barrier, and Codfish Islands, migrating to the Pacific coast of South America and the eastern Pacific Ocean. They eat mostly squid, crustaceans, and small fish, plucking prey from the surface of the water. Like other petrels and albatrosses, they have an upper stomach, used to store oil from their diet, and a lower stomach, where water, fat, and proteins are digested. The oil can move in small amounts into their lower stomach to provide energy as needed and can also be regurgitated to feed chicks. Chicks use the foul-smelling oil for defense, ejecting it onto predators. Breeding in colonies, they nest in burrows, where females lay a single egg. They are classified as Vulnerable by the IUCN, due to predation on their breeding islands from cats, rats, and Weka, a species of flightless rail that has been introduced to Codfish Island.