Cassin's Auklet

The Cassin's auklet, a small and chunky seabird, is a denizen of the North Pacific. This species, named after the esteemed American ornithologist John Cassin, is the sole member of the genus Ptychoramphus. With a modest length of 25 cm and a weight around 200 g, the auklet's plumage is predominantly dark above and lighter below, accented by a subtle white mark above the eye. Its bill is dark with a pale spot, and it sports blue feet. Unlike its more flamboyant auk relatives, the Cassin's auklet maintains a consistent appearance throughout the year.

Identification Tips

At sea, one might recognize the Cassin's auklet by its distinctive flight pattern, which has been likened to a "flying tennis ball." Its lack of dramatic breeding plumage sets it apart from other auks, making it a challenge to identify but for the practiced eye.

Habitat

The Cassin's auklet is a bird of the offshore islands, where it nests in small burrows, utilizing natural crevices or man-made structures as needed.

Distribution

This auklet's range extends from the Aleutian Islands and southern Alaska down to northern Baja California, and even to the Kurile Islands. Notably, a significant population resides on Triangle Island off Vancouver Island's Cape Scott, boasting an estimated 55,000 pairs.

Behaviour

The Cassin's auklet is a year-round resident in the southern parts of its range and demonstrates remarkable fidelity to its mate and nesting site across years. Both parents share the duty of incubating their single white egg, and they exchange shifts under the cover of night to evade predators. After a 40-day incubation, the chick is nourished nightly for 35 days with partially digested food from the parents' gular pouch. Remarkably, this species may lay a second clutch after a successful first, a rarity among northern hemisphere seabirds.

Breeding

Breeding begins for most individuals at around 3 years of age, with a high recruitment rate by the age of 8. The auklet's breeding propensity is notably high, and it demonstrates strong survival rates, though juvenile survival is lower.

Diet and Feeding

Cassin's auklets forage offshore, diving to impressive depths to pursue large zooplankton, with a particular fondness for krill. They are adept at underwater wing-propelled pursuit, capable of reaching depths of 30 meters, and possibly up to 80 meters.

Conservation status

The Cassin's auklet is currently listed as Near Threatened. Populations, particularly those on the Farallon Islands, have experienced significant declines. Threats include introduced predators, oil spills, and climatic shifts such as El Niño events. The species is protected under the Migratory Bird Treaty Act of 1918.