Monday, January 21, 2013

Swallow-tailed Gull

Swallow-tailed Gulls breed in Ecuador's Galapagos Islands and Columbia's Malpela Island. After breeding, this gull migrates widely along the Humboldt Current, from Peru to Panama. This photo was taken in the Galapagos, where breeding pairs, like many of the island's birds, are remarkably tame.

They eat squid and fish. Unique among gulls is this species' nocturnal feeding. The hypothesis is that Swallow-tailed Gulls have been driven into the night by frigatebirds, that are infamous for harassing and stealing prey from gulls. For whatever the reasons for their love of night, the result is that Swallow-tailed Gulls' eyes are larger in size and volume than any other gull (The Pacific Wildlife Foundation). This gull lacks a melatonin rhythm.  At night, diurnal gulls have high melatonin levels, which make vertebrates sleepy. Wikipedia warns, however, that we do not know if this relative lack of melatonin is the cause or an effect of the Swallow-tailed Gull's nocturnal habits.

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