LC
Crested Auklet Aethia cristatella



Justification

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). 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 extremely 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.

Population justification
The global population is estimated to number more than 8.2 million individuals, which equates to more than 5.5 million mature individuals (del Hoyo et al. 1996).

Trend justification
The population is suspected to be in decline owing to predation by invasive species, disturbance and pollution (del Hoyo et al. 1996).

Distribution and population

The Crested Auklet can be found in the north-west Pacific Ocean, specifically in the Bering Sea and Sea of Okhotsk (del Hoyo et al. 1996).

Ecology

This species can be found offshore and along sea coasts, breeding on remote islands and coasts utilizing scree slopes, boulder fields, lava flows and sea cliffs. It forages in deep water, usually far offshore, and concentrating on areas with dense aggregations of zooplankton (e.g. areas of converging currents or upwellings). It usually occurs in large flocks. Its diet comprises mainly planktonic crustaceans and infrequently small fish and squid. Individuals arrive at colonies between March and May, with the peak laying time varying depending on locality. Individuals are monogamous with high mate and site fidelity, and both sexes prefer mates with larger crests. Nest density in its sometimes large colonies (over 100,000 pairs) is determined by the availability of suitable rock crevices and cavities for nesting. Outside the breeding season it remains in the north-west Pacific (del Hoyo et al. 1996).

Threats

The species is sensitive to climate change, with chick survival being closely linked to dietary supplies of large zooplankton, whose range may be shifting in response to climatic changes, especially in the rapidly warming Bering Sea (Kitaysky and Golubova 2000). In 1996, the species was the most frequently harvested seabird in Alaska, with indigenous peoples permitted to hunt at any time. Despite c. 12,310 birds harvested per annum, this only amounts to a very small proportion of total population and has negligible effects on its trend. Introduced predators pose a threat in certain part of the species’ range with Arctic Vulpes lagopus and Red Foxes V. vulpes being introduced to 450 Aleutian islands by 1930 for fur farming and resulting in massive impacts on local bird populations. Following bird population collapses and eradication efforts, foxes were constrained to only 46 islands by 1996 (Veitch and Clout 2002). The species is vulnerable to oil spills due to large localised population concentrations.

Acknowledgements

Text account compilers
Hermes, C.

Contributors
Butchart, S., Calvert, R., Ekstrom, J., Fjagesund, T., Martin, R. & Miller, E.


Recommended citation
BirdLife International (2022) Species factsheet: Aethia cristatella. Downloaded from http://www.birdlife.org on 17/08/2022. Recommended citation for factsheets for more than one species: BirdLife International (2022) IUCN Red List for birds. Downloaded from http://www.birdlife.org on 17/08/2022.