August 19, 2011 § 1 Comment
August begins the nesting season for Swallow-Tailed Gulls on the island of Genovesa. Though some pairs can be found along the coast in the region they are near endemic to the Galapagos Islands. When not mating these gulls are pelagic, spending their time hunting the waters near Peru, Ecuador and north to the coast of Colombia.
These medium sized gulls are the only fully nocturnal gull in the world. Their nocturnal feeding habits scientists hypothesize are for survival. Frigate, the pirates of the bird world feed during the day by stealing the chicks and prey of other sea birds. Swallow tailed gulls that leave their cliff shelters during the day can be seen being chased by the frigates. Additionally Red-billed Tropicbirds which feed during the day were direct competition for food. However the tropicbirds are able to plunge dive (unlike the swallow-tailed gulls) which allows the tropicbirds to feed on prey below the surface while the gulls can only prey on that close to the top. To survive the swallow tailed gull’s eyes adapted to allow them to hunt at night feeding on fish and squid miles from shore.
Swallow tailed gulls nest in colonies through the eastern side of the Galapagos. Their nesting patterns are synchronized within the colony. The couple will make a rudimentary nest or platform out of a piece of lava, coral, twigs or sea urchin spines. The nest protects the egg from rolling off the cliffs edge. Though most gulls lay three eggs per season the swallow tail gulls typically only lay a single egg. The egg is incubated for just over a month. After it hatches both parents take turns feeding the hatchling. Once the chick is 60 – 70 days old it begins to take flight. Its parents will continue to feed it for another month until it leaves to feed on the open seas.