On 17 December Robert McNab reported a subadult, ABA Code-3 Masked Booby (Sula dactylatra) at the Dana Point Harbor breakwater in Orange County, California.
Like other Sulids, Masked Boobies are highly aerial while hunting and they obtain their food by plunge-diving. As a result, their flight feathers are molted almost continuously to ensure there are no periods when they are incapable of flight. To insure maximum streamlining they have evolved without brood patches and incubate their eggs with them placed on highly vasculated webs enabling heat transfer to the egg(s). Binocular vision in Sulids allows them to hunt at greater heights than other seabirds. Unlike some other Sulids that forage communally, Masked Boobies mostly forage alone. Unlike most Sulids that incubate only one egg, Masked Boobies incubate two and if both eggs hatch one chick dies as a result of “sibling murder”. The second egg has been described as an insurance policy with the result being a single chick like other booby species.
Masked is the largest booby enabling them to feed on larger prey items than other boobies. They seek shoal fish with flying fish being taken most often. They are a pantropical species and adults spend most of their lives near the breeding colonies while juveniles have been reported to disperse great distances Handbook of the Birds of the World, Volume 1).