Rhinoceros Auklet Life History

Habitat

Habitat Oceans

Rhinoceros Auklets nest on islands in the North Pacific, in colonies ranging from a few pairs to thousands of pairs. These islands may be forested or covered only in grasses, and they often have dense cover of salmonberry, willow, rose, or salal. During the breeding season, they forage close to colonies, often in places where tidal rips or upwelling concentrate prey or bring it closer to the surface. After the breeding season, they forage at sea, mostly over the continental shelf and continental slope, sometimes close to land but usually in deeper water beyond sight of land (50+ feet deep).

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Food

Food Fish

Rhinoceros Auklets eat primarily small, schooling fish or zooplankton, which they capture by diving and swimming underwater, using their wings for propulsion and feet for steering. They are capable of diving below 100 feet, but mostly they forage at depths less than 30 feet. They typically hunt fish from below, driving them up toward the surface. Some research suggests they may hunt cooperatively, forcing prey such as sandlance into “bait balls,” tight clusters of prey caught between the predators and the sea surface, where they are more readily caught. Rhinoceros Auklets often forage in large flocks, usually among other seabirds hunting the same prey, such as kittiwakes, loons, and many species of gull. Over much of their range, they are attracted to flocks of feeding kittiwakes, whose foraging activity is visible at great distances and indicates the presence of fish near the surface. Prey includes Pacific sandlance, peaceful sandlance, greenling, Pacific saury, capelin, northern anchovy, Japanese anchovy, night smelt, Pacific herring, sablefish, lingcod, Japanese pilchard, Pacific sardine, king salmon, various species of rockfish (genus Sebastes), California market squid, and many small crustaceans (euphausiids, copepods).

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Nesting

Nest Placement

Nest Burrow

On edges of islands, male and female excavate a long burrow in soil, in grassy areas or forest, well above the high tide line, as much as 650 feet from the sea.

Nest Description

Nest chambers are made at the end of a burrow that can be up to 20 feet long. The nest itself is a shallow, bowl-shaped depression, lined with grass, leaves, and twigs.

Nesting Facts

Egg Description:

Off white with faint purplish blotches.

Condition at Hatching:

Covered in down, can walk, but stay in nest.

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Behavior

Behavior Surface Dive

Because they are mostly nocturnal on the breeding grounds, little is known about Rhinoceros Auklets breeding behavior. As with the closely related puffins, these auklets seem to form and maintain pair bonds with courtship displays that involve marching in hunched postures, upright stances, bowing, billing (in which male and female tap their beaks together), and head movements. These can happen at sea and at the nest entrance. The species is apparently monogamous in its mating system, and individuals often repartner with the same mate from previous nesting seasons. When feeding young, Rhinoceros Auklets typically gather offshore in late afternoon, waiting for darkness before returning to the nest burrow. At sunset, they begin to fly in, then circle over the colony before going to their nests.

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Conservation

Conservation Low Concern

Rhinoceros Auklets are relatively common throughout their range, although little is known about their population trends. In 2002, the North American Waterbird Conservation Plan estimated a continental breeding population of 922,000 birds. In 2017, Partners in Flight estimated a global breeding population of 1.5 million birds and rated the species a 12 out of 20 on the Continental Concern Score, indicating a species of low conservation concern. Threats to this species include introduced mammal predators on nesting islands, entanglement in fishing gear, pesticide poisoning, oil spills and oil pollution, and climate change.

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Credits

Gaston, Anthony J. and S. B. Dechesne. (1996). Rhinoceros Auklet (Cerorhinca monocerata), version 2.0. In The Birds of North America (P. G. Rodewald, editor). Cornell Lab of Ornithology, Ithaca, New York, USA.

Kushlan, J. A., M. J. Steinkamp, K. C. Parsons, J. Capp, M. A. Cruz, M. Coulter, I. Davidson, L. Dickson, N. Edelson, R. Elliott, R. M. Erwin, S. Hatch, S. Kress, R. Milko, S. Miller, K. Mills, R. Paul, R. Phillips, J. E. Saliva, W. Sydeman, J. Trapp, J. Wheeler and K. Wohl (2002). Waterbird conservation for the Americas: The North American waterbird conservation plan, version 1. Washington, DC, USA.

Lutmerding, J. A. and A. S. Love. (2019). Longevity records of North American birds. Version 1019 Patuxent Wildlife Research Center, Bird Banding Laboratory 2019.

Partners in Flight (2017). Avian Conservation Assessment Database. 2017.

Sibley, D. A. (2014). The Sibley Guide to Birds, second edition. Alfred A. Knopf, New York, NY, USA.

Wilkinson, B. P., M. E. Johns, and P. Warzybok. (2019.) Fluorescent ornamentation in the Rhinoceros Auklet Cerorhinca monocerata. Ibis 161: 694-698. https://doi.org/10.1111/ibi.12715

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