The Cassin's auklet is a small, chunky seabird that ranges widely in the North Pacific. It is noteworthy for its extraordinary diving ability and skill at catching prey underwater. The Channel Islands National Park is a major breeding and feeding grounds for this species. The park provides the isolation required for its nesting sites providing the environment required to maintain its population.
Quick and Cool Facts
- Cassin's auklets breed along the Pacific coast, from midways up the Baja California peninsula to Alaska's Aleutian Islands. On the Channel Islands, the Cassin's auklet currently nests on Santa Barbara, Santa Cruz, San Miguel, and Anacapa Islands.
- During the non-breeding seasons, Cassin's auklets will spend most of their time at sea.
- Cassin's auklets nest in rock crevices and build burrows.
- They will also nest in artificial burrows allowing biologists to easily monitor a colon.
- Both parents incubate a single egg.
- Cassin's auklets are excellent divers; their wings allow them to "fly underwater.
- During the nesting season, food is stored in a specialized throat pouch and brought back to the nesting site. They return to their nest only at night.
The Cassin's auklet is a small (10 in., 7 oz.) nondescript auk. Its plumage is generally dark above and pale below, with a small white mark above the eye. Its bill is overall dark with a pale spot, and its feet are blue. Unlike many other auks, the Cassin's auklet lacks dramatic breeding plumage, remaining the same over most of the year. At sea it is usually identified by its flight, which is described as looking like a flying tennis ball.
The Cassin's auklet ranges from midway up the Baja California peninsula to Alaska's Aleutian Islands off North America. It nests on offshore islands, with the main population stronghold at Triangle Island off Vancouver Island's Cape Scott, where the population is estimated to be around 550,000 pairs.
San Miguel Island and its islets, particularly Prince Island and Castle Rock, provide the most important nesting sites for the Cassin's auklet in the Southern California bight. It also breeds colonially on the other islands of the Channel Islands National Park, except Santa Rosa Island. The Cassin's auklet usually nest in dense colonies in rock crevices and in burrows they dig in rocky compacted soil or they may excavate burrows for nesting in soft soils under vegetation, stumps, or fallen logs on seaward slopes of coastal sites.
The Cassin's auklet feeds offshore, often relying on upwellings of cooler nutrient rich waters and associating with bathymetric landmarks such the continental shelf and underwater canyons. This species unique ability to dive by beating its wings for propulsion allows it to hunt down large zooplankton, especially krill. It can dive to 30 meters below the surface, and by some estimates 80 meters.
The Cassin's auklet may be found in the breeding colony year round. Auklet pairs show a strong loyalty towards each other, nesting on the same site for many years. Parents take turns incubating a single white egg, with the at-sea parent returning after dusk to swap shifts in order to avoid predators such as the western gull or peregrine falcon. The egg is incubated for 40 days. The small chick is then fed nightly for 35 days by both parents, who regurgitate partially digested food (krill and other small crustaceans) carried in a special gular pouch, often referred to as a sublingual pouch. The chick fledges alone and makes its way to the sea. The Cassin's auklet is unusual amongst seabirds because it will occasionally lay a second clutch after a successful first clutch.
This seabird is not recognized as the migratory bird, however the northern birds may move southward during the winter season toward ice-free areas. Populations on the west coast are generallypermanent residents.
The Cassin's auklet is listed as Least Concern. Although some populations (principally the Farallon Islands population) have suffered steep declines since the early 1970's, the species is still numerous overall. Threats to the auklet include introduced carnivores (particularly in Alaska), oil spills, and changes in sea surface temperature (caused by El Niño events). The Cassin's auklet is protected under the Migratory Bird Treaty Act of 1918.On Santa Barbara Island, efforts are underway to restore seabird nesting habitat for Cassin's auklets by removing non-native plants and planting native vegetation to improve seabird habitat. Nest boxes insulated against the elements have also been installed with the goal of providing a secure nesting area and vocalization playback systems have been used to attract auklets. Scorpion and Orizaba Rocks, located off of Santa Cruz Island, are also important nesting islets for Cassin's aucklets. To restore seabird habitat on these islets, restoration efforts have included removing non-native vegetation, revegetation with native plants, installation of nest boxes, and signs informing the public that the rocks are closed to protect nesting seabirds. Visit Seabirds to learn more about these restoration efforts