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Cassin's Auklet Ptychoramphus aleuticus

This species has been uplisted to Near Threatened because the global population decline is likely to approach 30% in three generations (23 years). If the decline is found to be larger then the species could qualify for further uplisting; it almost meets the requirements for listing as threatened under criteria A2b+3b+4b.

Taxonomic source(s)
del Hoyo, J.; Collar, N. J.; Christie, D. A.; Elliott, A.; Fishpool, L. D. C. 2014. HBW and BirdLife International Illustrated Checklist of the Birds of the World. Barcelona, Spain and Cambridge UK: Lynx Edicions and BirdLife International.

23 cm small, plump alcid. Short blackish/grey bill, base of lower mandible yellowish. Iris white, white crescent above eye. Dark greyish brown head with paler brown chin and throat. Upperparts blackish to slate grey with greyish brown breast and flanks, white belly. Legs and feet bluish pink, with black claws. No marked seasonal variation. Juvenile has whiter throat, browner wings and tail and dark brown iris (Nettleship 1996).

Distribution and population
The species ranges from Baja California (Mexico) up the Pacific coast of the U.S.A. and Canada, through Alaska to the Aleutian Islands (U.S.A.) (del Hoyo et al. 1996). British Columbia (Canada) supports the largest population with approximately 2,700,000 breeding birds; it is estimated that there are approximately 600,000 birds in Alaska, 88,000 in Washington, 500 in Oregon, 131,000 in California and 20,000-40,000 in Baja California on the islands of San Benito, San Geronimo, Asuncion and San Roque (Nettleship 1996).

Population justification
The total population is estimated to be at least 3,600,000 breeding birds (Nettleship 1996) which equates to approximately 5,400,000 individuals.

Trend justification
This species has apparently undergone a large and statistically significant decrease over the last 40 years in North America (-96.8% decline over 40 years, equating to a -57.9% decline per decade; data from Breeding Bird Survey and/or Christmas Bird Count: Butcher and Niven 2007, although these surveys cover less than 50% of the species's range in North America). A recent study by Rodway and Lemon (2011) found declines in monitored burrows at several colonies in British Columbia, and estimated a 40% decline in monitored burrows over 20 years between 1989 and 2009 in the largest known breeding population on Triangle Island (part of the Scott Islands). Declines appear to have begun in c.1990, and if the declines on Triangle Island are representative of the whole Scott Islands population then there could have been a total loss of approximately 800,000 birds in the region, or >20% of the world breeding population. Large-scale declines have also been documented on the South Farallon Islands, California (H. Carter in litt. 2013). The overall rate of decline is currently placed in the band 20-29% in three generations (23 years), but confirmation that similar declines are taking place across the whole range would lead to the overall rate of decline being increased.

This species is found offshore and along sea coasts, mostly over the continental shelf to the edge but also beyond into deep ocean. It feeds mostly on crustaceans throughout the year, supplemented by other invertebrates and small larval fish. The start of the breeding season varies greatly with latitude, from November in Baja California to July in Alaska. Birds form colonies from under 500 birds to over one million, usually at high densities on coastal islands with or without trees and nesting on a wide range of habitats. It winters mainly offshore within the breeding range, with southerly populations being relatively sedentary compared to northern individuals which migrate south (del Hoyo et al. 1996).

Introduced predators including rats (Rattus rattus and R. norvegicus), cats, foxes and grazing animals, such as goats represent the most serious threat to colonies (Nettleship 1996, Rodway and Lemon 2011). Raccoons (Procyon lotor) are also a threat on some islands in British Columbia (Rodway and Lemon 2011). Oil pollution represents a significant threat and oil and gas extraction operations may impact negatively on the species through increased pollution and collision with lights (Harfenist 2004). Accidental bycatch in fishing nets is also considered a threat (Harfenist 2004). The species is vulnerable to loss of habitat and disturbance owing to tourism development, recreational and research activities as well as aquaculture and logging operations (Nettleship 1996). The species may be vulnerable to collisions with wind turbines. Losses have also been attributed to increases in numbers of Bald Eagles Haliaeetus leucocephalus, Peregrine Falcon Falco peregrinus and Western Gulls Larus occidentalis in some areas (Nettleship 1996). Fluctuations in the northern Californian populations may be partially explained by anomalous warm-water conditions (Nettleship 1996) which are also thought to be responsible for mass die-offs reported from California to central British Columbia in 2014 (Welch 2015). The species is vulnerable to the effects of climate change, particularly changes in coastal upwelling systems (Wolf et al. 2010).

Conservation and Research Actions Underway
The species, its eggs and nests are protected from hunting and collecting in the U.S.A. and Canada under the Migratory Birds Convention Act (Harfenist 2004). In 2002 a rat eradication programme was carried out on Ancapa Island, California. Within one year Cassin's Auklet nests were detected on the island and between 2003 and 2012 a total of 42 nests were discovered (Whitworth et al. 2015). Rat eradications have been carried out in other areas of the species's range, including Langara Island, British Columbia (Regehr et al. 2007).

Conservation and Research Actions Proposed
Implement control programmes at breeding sites to remove invasive predators and problematic livestock (Nettleship 1996). Protect colonies from direct human disturbance. Restrict gill-net fishery operations close to colonies. Develop monitoring programmes to assess changes in population size.

Related state of the world's birds case studies

Bertram, D. F.; Mackas, D. L.; McKinnell, S. M. 2001. The seasonal cycle revisited: interannual variation and ecosystem consequences. Progress in Oceanography 49: 283-307.

del Hoyo, J., Elliott, A., and Sargatal, J. 1996. Handbook of the Birds of the World, vol. 3: Hoatzin to Auks. Lynx Edicions, Barcelona, Spain.

Harfenist, A. 2004. Cassin's Auklet - Ptychoramphus aleuticus. Accounts and Measures for Managing Identified Wildlife - Accounts V. 2004. Ministry of Environment British Columbia.

IUCN. 2015. The IUCN Red List of Threatened Species. Version 2015-4. Available at: (Accessed: 19 November 2015).

Lee, D .E.; Nur, N.; Sydeman, W. J. 2007. Climate and demography of the planktivorous Cassin's Auklet Ptychoramphus aleuticus off northern California: implications for population change. Journal of Animal Ecology 76: 337-347.

Nettleship, D.N. 1996. Cassin's Auklet (Ptychoramphus aleuticus). In: del Hoyo, J., Elliott, A., Sargatal, J., Christie, D.A. and de Juana, E. (eds), Handbook of the Birds of the World Alive, Lynx Edicions, Barcelona.

Regehr, H.M., Rodway, M.S., Lemon, M.J.F. and Hipfner, J.M. 2007. Recovery of the Ancient Murrelet Synthliboramphus antiquus colony on Langara Island, British Columbia, following eradication of invasive rats. Marine Ornithology 35: 137-144.

Rodway, M.S. and Lemon, M.J.F. 2011. Use of permanent plots to monitor trends in burrow-nesting seabird population in British Columbia. Marine Ornithology 39: 243-253.

Welch, C. 2015. Mass Death of Seabirds in Western U.S. Is 'Unprecedented'. National Geographic. Available at: (Accessed: 02/09/2015).

Whitworth, D.L., Harvey, A.L., Carter, H.R., Young, R.J., Koepke, J.S. and Mazurkiewicz, D.M. 2015. Breeding of Cassin's Auklets Ptychoramphus aleuticus at Anacapa Island, California, after eradication of Black Rats Rattus rattus. Marine Ornithology 43(1): 19-24.

Wolf, S.G., Snyder, M.A., Sydeman, W.J., Doak, D.F. and Croll, D.A. 2010. Predicting population consequences of ocean climate change for an ecosystem sentinel, the seabird Cassin's auklet. Global Change Biology 16: 1923-1935.

Further web sources of information
Explore HBW Alive for further information on this species

Search for photos and videos, and hear sounds of this species from the Internet Bird Collection

Text account compilers
Butchart, S., Calvert, R., Ekstrom, J. & Ashpole, J

Carter, H.

IUCN Red List evaluators
Symes, A.

Recommended citation
BirdLife International (2015) Species factsheet: Ptychoramphus aleuticus. Downloaded from on 26/11/2015. Recommended citation for factsheets for more than one species: BirdLife International (2015) IUCN Red List for birds. Downloaded from on 26/11/2015.

This information is based upon, and updates, the information published in BirdLife International (2000) Threatened birds of the world. Barcelona and Cambridge, UK: Lynx Edicions and BirdLife International, BirdLife International (2004) Threatened birds of the world 2004 CD-ROM and BirdLife International (2008) Threatened birds of the world 2008 CD-ROM. These sources provide the information for species accounts for the birds on the IUCN Red List.

To provide new information to update this factsheet or to correct any errors, please email BirdLife

To contribute to discussions on the evaluation of the IUCN Red List status of Globally Threatened Birds, please visit BirdLife's Globally Threatened Bird Forums.

Key facts
Current IUCN Red List category Near Threatened
Family Alcidae (Auks)
Species name author (Pallas, 1811)
Population size 2500000-4999999 mature individuals
Population trend Decreasing
Distribution size (breeding/resident) 123,000 km2
Country endemic? No
Links to further information
- Additional Information on this species