In early November, seabird biologists discovered Brown Boobies actively nesting on an island in Channel Islands National Park. It was the first breeding record of the species in California and signifies a significant northward expansion of its breeding range.
The biologists observed four nests and 102 individual birds on Sutil Island, off the southwest end of Santa Barbara Island, the smallest island in the park. The adult birds appeared to be incubating eggs or possibly tending to small young on the four nests.
The adult breeding pairs displayed characteristic mating behavior such as pair swapping, a practice of taking turns tending to the nest, and defending the nests from invading Western Gulls.
Brown Boobies, generally considered tropical or subtropical birds, appear to have been extending their range northward since the 1990s, when the birds moved northward from the Gulf of California and the Pacific coast of Mexico to the Coronado Islands in the ocean off northern Baja California.
The park said the expansion of their range coincides with shifts in oceanic conditions with warmer waters and changes in prey availability associated with recent El Niño events.
An impressive seabird species, Brown Boobies are known for making spectacular plunge dives from heights of up to 50 feet to feed on surface fish. They nest on islands, laying their eggs on the bare ground, and making nests with sticks, rocks, bones, and vegetation to protect them. They winter far out to sea.
Worldwide, booby populations have declined due to habitat degradation on islands, where introduced predators have reduced their nesting success.
Read our newsletter!
Sign up for our free e-newsletter to receive news, photos of birds, attracting and ID tips, and more delivered to your inbox every other week. Sign up now