Justification of Red List Category
This species has an extremely large range, and hence does not approach the thresholds for Vulnerable under the range size criterion (Extent of Occurrence <20,000 km2 combined with a declining or fluctuating range size, habitat extent/quality, or population size and a small number of locations or severe fragmentation). The population trend appears to be stable, and hence the species does not approach the thresholds for Vulnerable under the population trend criterion (>30% decline over ten years or three generations). The population size is very large, and hence does not approach the thresholds for Vulnerable under the population size criterion (<10,000 mature individuals with a continuing decline estimated to be >10% in ten years or three generations, or with a specified population structure). For these reasons the species is evaluated as Least Concern.
The global population was estimated to number 235,000 individuals in 1993 (del Hoyo et al. 1996).
The overall trend is likely to be stable. In North America, this species has undergone a small or statistically insignificant increase over the last 40 years (data from Breeding Bird Survey and/or Christmas Bird Count: Butcher and Niven 2007). Note, however, that these surveys cover less than 50% of the species's range in North America.
The Pigeon Guillemot can be found in the North Pacific, breeding from the Kuril Islands (Russia), on the Kamchatka Peninsula to the eastern tip of Siberia (Russia), and from the western tip of Alaska (U.S.A.) down through the Atlantic coast of Canada to southern California (U.S.A.) and northern Mexico, including colonies on the Commander and Aleutian Islands (del Hoyo et al. 1996).
This marine species can be found along rocky coastlines of the North Pacific. Its diet includes a wide variety of small benthic fish and invertebrates, widening to include more species in the summer. Chicks are usually fed fish which tend to be obtained within 1 km of the colony. It normally arrives at colonies between March and April, breeding on sea cliffs and slopes close to regions of shallow water usually less than 50 m deep. It is a monogamous species with high mate and site fidelity, usually breeding in small colonies of under 50 birds, sometimes as single pairs, but colonies of over 1000 birds have been seen. Individuals normally remain near colonies outside the breeding season, though birds from Alaska and California move south and north respectively (del Hoyo et al. 1996).
Certain colonies are vulnerable to oil spills and non-native predators (e.g. foxes), but the species's widespread distribution is thought to offset localised threats. Local declines have been recorded in colonies along the west coast of the U.S.A. (California, Oregon), attributed to oil pollution, human disturbance and warm-water years, while the steady decline in the Prince William Sound colony since 1972 is largely unaccounted for, though probably accentuated by the 1989 Exxon Valdez oil spill. Incidental capture in inshore gill-net fisheries is another cause of mortality, but likely only affecting colonies on a local scale (Nettleship et al. 2018).
Text account compilers
Butchart, S., Ekstrom, J., Fjagesund, T., Calvert, R., Martin, R.
BirdLife International (2021) Species factsheet: Cepphus columba. Downloaded from http://www.birdlife.org on 23/06/2021. Recommended citation for factsheets for more than one species: BirdLife International (2021) IUCN Red List for birds. Downloaded from http://www.birdlife.org on 23/06/2021.