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T H E S C O T T I S L A N D S
Cassin's Auklet
(Ptychoramphus aleuticus)
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Cassin's auklet |
Characteristics
The Cassin's auklet is a small member of the Alcidae family. The bird weighs less than 200 grams, and is mostly grey-brown with a white belly, white eyebrows and blue feet. It has a short, dark bill with an obscure yellow base. The juvenile looks similar to the adult, but is paler and has a white throat. Like penguins, Cassin's auklets possess the unique ability to “fly” underwater using wings as flippers. Despite their considerable numbers, they are rarely seen in BC waters, spending most of their lives on the open ocean. They come ashore only during the nesting season, arriving on the colony well after dark and returning to sea before dawn. They only remain ashore in daytime when incubating eggs or brooding small chicks.
Breeding and Feeding
Cassin's auklets breed in colonies on isolated islands. Thousands of birds gather at the same location to raise their young. To nest, they dig burrows with their bills and feet. The female lays a single white egg at the deep end of the burrow. The parents take turns incubating the egg in 24-hour shifts. After the chick hatches, about 38 days after the egg was laid, both parents typically return once each night to feed zooplankton to the chick (mainly copepods and euphausiids, and some larval fish). The birds forage up to 80 kilometres from the colony, carrying the food back to the chick in a unique throat pouch. The chick “sips” the bright pink, soupy zooplankton directly from the parent's throat. When the chick is old enough to be left on its own, both parents forage during the day and return at night to feed the chick. At about 45 days, the chick fledges to begin an independent life at sea. Two or three years later, it will return as an adult to find a mate and breed.
Status
Cassin's auklets are distributed only in the northeastern Pacific Ocean from the Aleutian Islands south to Baja California. The two million that breed on the Scott Islands represent 55% of the entire global population, or 70% of the national population. Triangle Island alone supports the world's single largest colony with an estimated 548,000 breeding pairs. Cassin's auklets are distributed on outer coastal waters throughout most of the year, and rarely come near shore. The birds tend to aggregate near zooplankton, their primary food item. Cassin's auklet is blue-listed in BC. This provincial designation means the species is not immediately threatened, but of concern because of characteristics that make it particularly sensitive to human activities or natural events.
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