Justification of Red List Category
This species has a very 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). Despite the fact that the population trend appears to be decreasing, the decline is not believed to be sufficiently rapid to 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 is estimated to number c.140,000-148,000 individuals (del Hoyo et al. 1996), while national population sizes have been estimated at <100 breeding pairs and c.50-1,000 wintering individuals in Japan and c.100-100,000 breeding pairs and c.50-10,000 individuals on migration in Russia (Brazil 2009).
The population is suspected to be in decline owing to predation by invasive species and food shortages caused by the depletion of fisheries (del Hoyo et al. 1996).
The Spectacled Guillemot is found on coasts and islands of the north-west Pacific, breeding from the Kamchatkan Peninsula, Russia, and Sea of Okhotsk to the north-east North Korea, including the Kuril Islands, and Hokkaido, Japan. It winters near the breeding locations and beyond the southern tip of Japan (del Hoyo et al. 1996).
This exclusively marine species is found near-shore whilst breeding and over both pelagic waters and along coasts during the winter. It feeds largely on fish with a few invertebrates, usually catching prey close to breeding colonies. Its breeding season probably begins between April and May, nesting either as a single pair, in groups of 10-20 pairs and rarely in large colonies of 200-300 pairs. It lays in cliff crevices, in holes and cavities in scree slopes and boulder fields or, on predator-free islands, in more accessible sites. Individuals are resident and mostly sedentary, remaining in the vicinity of the colonies except in the north of the range (del Hoyo et al. 1996).
The species is listed as Vulnerable in Japan; 19 Japanese colonies have seemingly disappeared, and the populations decreased in twelve of the remaining colonies (14 known + 4 suspected breeding colonies) (Senzaki et al. 2015). The drivers of these apparent local extinctions are unknown, with small colony size being the best predictor of disappearance (Senzaki et al. 2015). The decline in the Shiretoko Peninsula population has been attributed to frequent disturbance by high-speed sightseeing boats, which appear to have displaced breeding sites (Fukuda 2010) and have been demonstrated to alter the daily activity pattern of Spectacled Guillemots (Senzaki et al. 2015). Although the causes of decline remain uncertain in large parts of the species's range, likely threats include food shortages caused by the overexploitation of fish stocks, bycatch (Senzaki et al. 2015), predation by invasive species (fox, Sable, rats), human disturbance and illegal hunting (Nettleship et al. 2018).
Text account compilers
Ekstrom, J., Fjagesund, T., Calvert, R., Butchart, S., Martin, R., Miller, E.
BirdLife International (2020) Species factsheet: Cepphus carbo. Downloaded from http://www.birdlife.org on 31/05/2020. Recommended citation for factsheets for more than one species: BirdLife International (2020) IUCN Red List for birds. Downloaded from http://www.birdlife.org on 31/05/2020.