CDC Logo

BC Conservation Data Centre: Species Summary

Cerorhinca monocerata
Rhinoceros Auklet

Scientific Name: Cerorhinca monocerata (Pallas, 1811)
English Name: Rhinoceros Auklet
Classification / Taxonomy
Scientific Name - Concept Reference: American Ornithologists' Union (AOU). 1998. Check-list of North American birds. Seventh edition. American Ornithologists' Union, Washington, D.C. [as modified by subsequent supplements and corrections published in The Auk]. Also available online:
Classification Level: Species
Species Group: Vertebrate Animal
Species Code: B-RHAU
Kingdom Phylum Class Order Family
Animalia Craniata Aves Charadriiformes Alcidae
Conservation Status / Legal Designation
Global Status: G5 (Apr 2016)
Provincial Status: S4 (Mar 2016)
BC List: Yellow
Provincial FRPA list:   
Provincial Wildlife Act:
SARA Schedule:
General Status Canada: 4 - Secure (2005)
Migratory Bird Convention Act: Y
Ecology & Life History
General Description: A large, chunky, seabird with a large head and bill and a short thick neck; upperparts are blackish brown, with paler sides, neck, and throat; belly white, grading into dark breast; adults in breeding plumage (acquired in winter) have two prominent white plume streaks on each side of the head (indistinct in basic plumage) and a yellow, upward-directed horn at the base of the orange or yellowish bill (horn is absent in nonbreeding plumage); immatures lack the horn and the white head plumes, and the bill is dusky and the eyes are darker; average length 38 cm (NGS 1983).
Global Reproduction Comments: Egg are laid May-June in Alaska and British Columbia, late April-June in Washington. Clutch size is 1. Incubation lasts 39-52 days (average 46), by both sexes. Nestling period lasts 40-70 days (reported means: 52-55 days) (Harfenist 1995, Auk 112:60-66). One or both parents may feed the chick each night. Young independent while they complete development at sea after fledging. Appears to retain same mate in subsequent years. Breeding success of about 50-60% may be typical (Johnsgard 1987). Nesting density sometimes >1 nest burrow per sq m.
Global Ecology Comments: Usually seen alone or in small groups on the ocean.

Introduced arctic fox (predator) may explain absence throughout almost all of Aleutian chain. Commonly preyed on by great horned owl on Protection Island, Washington (Hayward et al., 1993, Auk 110:133-135).
Migration Characteristics:
(Global / Provincial)
    Local Migrant:
    Distant Migrant:
    Within Borders Migrant:
N /
Y /
Y /
na /
Global Migration Comments: Auklets from British Columbia probably winter off the coasts of California and Oregon.
(Type / Subtype / Dependence)
Grassland/Shrub / Meadow / Unknown
Grassland/Shrub / Shrub - Natural / Unknown
Ocean / Marine Island / Unknown
Ocean / Pelagic / Unknown
Ocean / Sheltered Waters - Marine / Unknown
Global Habitat Comments: Nonbreeding: mostly pelagic, less frequently along rocky seacoasts (AOU 1983).

Nests in burrow mainly on grassy or shrubby sea-facing slope or level area near edge of island; small numbers of nests on cliffs or steep slopes (Wilson and Manuwal 1986); also recorded nesting in caves in Oregon and California. Often uses same nest site in successive years. Readily accepts artificial burrows (see Spendelow and Patton 1988). See Spendelow and Patton (1988) for further details on nesting habitat in Washington and British Columbia.
Food Habits: Invertivore: Adult, Immature
Piscivore: Adult, Immature
Global Food Habits Comments: Eats small fishes, crustaceans, squid. Dives under water after prey. Chick diet varies among years and localities; predominant species may include Pacific sandlance, Pacific herring, night smelt, Pacific saury, rockfish, anchovy, juvenile salmon, etc. Off British Columbia, epipelagic schooling fishes were the prey most often delivered to chicks; most foraging occurred in the upper 10 m, though most birds sometimes dove to 20-60 m; usually foraged in water considerably deeper than 15 m (Burger et al. 1993).
Global Phenology: Crepuscular: Adult, Immature
Diurnal: Adult, Immature
Nocturnal: Adult, Immature
Global Phenology Comments: May be active diurnally at breeding colonies in California and Oregon, but activity at breeding colony mostly nocturnal farther north (Wilson and Manuwal 1986, Spendelow and Patton 1988).
Provincial Phenology:
(1st half of month/
2nd half of month)
Colonial Breeder: Y
Length(cm)/width(cm)/Weight(g): 38/ / 520
Elevation (m) (min / max): Global: 
Endemic: N
Global Range Comment: BREEDING: islands along Pacific coast of North America, south-coastal and southeastern Alaska south to central California; eastern Asia from southern Sakhalin and southern Kurile islands south to Korea, Japan. NON-BREEDING: off Pacific coast from southern British Columbia south to Baja California; also in Asia (AOU 1983).
Authors / Contributors
Global Information Author: Hammerson, G.
Last Updated: Apr 05, 1996
Provincial Information Author:
Last Updated:
References and Related Literature
American Ornithologists' Union (AOU). 1983. Check-list of North American Birds, 6th edition. Allen Press, Inc., Lawrence, Kansas. 877 pp.
Burger, A. E., et al. 1993. Diving depths, diet, and underwater foraging of rhinoceros auklets in British Columbia. Can. J. Zool. 71:2528-2540.
Campbell, R.W., N.K. Dawe, I. McTaggart-Cowan, J.M. Cooper, G.W. Kaiser, and M.C.E. McNall. 1990b. The Birds of British Columbia Vol. 2: Nonpasserines: Diurnal Birds of Prey through Woodpeckers. Royal British Columbia Museum, Victoria, BC.
Golovkin, A. N. 1984. Seabirds nesting in the USSR: the status and protection of populations. Pages 473-486 in Croxall et al., eds. Status and conservation of the world's seabirds. ICBP Tech. Pub. No. 2.
Harrison, C. 1978. A Field Guide to the Nests, Eggs and Nestlings of North American Birds. Collins, Cleveland, Ohio.
Hasegawa, H. 1984. Status and conservation of seabirds in Japan, with special attention to the short-tailed albatross. Pages 487-500 in Croxall et al., eds. Status and conservation of the world's seabirds. ICBP Tech. Pub. No. 2.
Hatch, S. A., and M. A. Hatch. 1990. Breeding seasons of oceanic birds in a subarctic colony. Can. J. Zool. 68:1664-1679.
Hyslop, C., and J. Kennedy, editors. 1992. Bird trends: a report on results of national ornithological surveys in Canada. Number 2, Autumn 1992. Migratory Birds Conservation Division, Canadian Wildlife Service, Ottawa, Ontario. 20 pp.
Johnsgard, P. A. 1987. Diving birds of North America. Univ. Nebraska Press, Lincoln. xii + 292 pp.
Lensink, C. J. 1984. The status and conservation of seabirds in Alaska. Pages 13-27 in Croxall et al., eds. Status and conservation of the world's seabirds. ICBP Tech. Publ. No. 2.
National Geographic Society (NGS). 1983. Field guide to the birds of North America. National Geographic Society, Washington, DC.
Sealy, S. G., editor. 1990. Auks at sea. Western Foundation of Vertebrate Zoology, Studies in Avian Biology No. 14. vi + 180 pp.
Spendelow, J. A. and S. R. Patton. 1988. National Atlas of Coastal Waterbird Colonies in the Contiguous United States: 1976-1982. U.S. Fish and Wildlife Service, Biological Report 88(5). x + 326 pp.
Terres, J. K. 1980. The Audubon Society encyclopedia of North American birds. Alfred A. Knopf, New York.
Wilson, U. W., and D. A. Manuwal. 1986. Breeding biology of the rhinoceros auklet in Washington. Condor 88:143-155.

Please visit the website Conservation Status Ranks for definitions of the data fields used in this summary report.

Suggested Citation:

B.C. Conservation Data Centre. 1996. Species Summary: Cerorhinca monocerata. B.C. Minist. of Environment. Available: (accessed Feb 6, 2023).