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Rhinoceros Auklets Rhinoceros Auklet
Rhinoceros Auklets
(Cerorhinca monocerata)
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The rhinoceros auklet is an unusual member of the Alcidae family. It is actually a puffin, not an auklet; its outward appearance does differ noticeably from other puffins.

Ranges widely across the Northern Pacific. Breeds from the Aleutians south to central California. Winter off breeding grounds and south to southern California and in Northern Asia.

Terrestrial predators such as foxes, mink, raccoons, cats and rats can enter burrows and eat eggs, chicks, and adults. Gulls. Raptors.

Most of their diet is composed of small fish including: Pacific sand lance, smelt, herring, anchovies, rockfish, crustaceans and squid.

A pigeon-sized seabird. 14 1/2-15 1/2" (37-39 cm). A medium-sized bird at 500 grams. Males are slightly larger than females (about 10% in mass).

Life Span
Around seven to eight years.

Rhinoceros auklets begin to breed at 3-5 years of age. Nests in colonies on isolated islands, where thousands of birds gather to raise their chicks. Rhinoceros Auklets dig burrows in the ground on both forested and non-forested islands. Burrows can be up to 20 feet long and often fork many times. At the end of each burrow is a nest chamber with a shallow cup of moss and twigs.

The female lays one egg, and both parents incubate for 5-1/2 to 7-1/2 weeks. The Rhinoceros Auklets will carry 3-6 fish at a time 30 miles back to their burrow-nests where chicks wait to be fed. Both adults forage and feed the chick, which fledges at the age of 7 or 8 weeks.

Adults will readily abandon their nests if disturbed during the incubation or brooding periods. In addition, burrows are often near the surface and collapse easily if trod upon.

Seasonal Change
Closely related to the Tufted Puffin, the Rhinoceros Auklet is a medium-sized alcid with a wedge-shaped head. It is drab-gray overall, darker above than below. In breeding plumage, the Rhinoceros Auklet has a bright orange-yellow bill adorned with a whitish horn. It also has two light feather tufts on each side of its head, going in a line back from the eye and the corner of the mouth. The juvenile appears similar to the non-breeding adult, lacking both the feather tufts and beak horn, although the lower mandible is yellow on the adult and dark on the juvenile.

Morphology and Function
The Rhinoceros Auklets capture prey through wing-propelled pursuit-diving. From a resting position on the water, they duck under the surface, then beat their wings and "fly" underwater to snap up fish with a laterally compressed bill. They can hold several fish at a time crosswise.
They have an extraordinary diving ability; they have been recorded as deep as 300 feet or more below the surface. Their dense, waterproof wings are adapted for underwater propulsion, and their strong bones resist crushing water pressures at great depths. Enhanced oxygen-storing capacity and the ability to use anaerobic respiration during long dives allow the auklet to stay underwater for up to two minutes.
Their flight is fast and close to the water's surface at 35 to 50 miles per hour.

Other Facts
The species is mostly nocturnal. During the day, the Rhinoceros Auklets tend to stay on the water. On land, they remain hidden in the burrows. During the night, the auklets compete for nesting spots, dig burrows, lay eggs, and feed their young.

Rhinoceros Auklets are the only extant (presently living) species in their genus, Cerorhinca.

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