Swallow-tailed gull and hunting over the open oceans, and migrating eastward to the coasts of Ecuador and Peru. The swallow-tailed gull is unique among the gulls in feeding exclusively nocturnally, mostly on fish and squid which rise to the surface at night to feed on plankton. It leaves the colony as a flock at dusk, with a great deal of screaming and display. Calls and displays are quite different from other gulls, most resembling the vocalisations of the black-legged kittiwake and Sabine's gull. The loudest and most commonly heard call is an alarm referred to as "rattle-and-whistle", a gurgling scream made with
Gull species and only one egg for the swallow-tailed gull. Within colonies, birds synchronise their laying, with synchronisation being higher in larger colonies, although after a certain point, this levels off. The eggs of gulls are usually dark tan to brown or dark olive with dark splotches and scrawl markings, and are well camouflaged. Both sexes incubate the eggs, with incubation bouts lasting between one and four hours during the day and one parent incubating through the night. Research on various bird species including the gull suggests that females form pair bonds with other females to obtain alloparental care for their