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). The population trend appears to be increasing, 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.
del Hoyo et al. (1992) estimated the global population to number 526,000 individuals. In Europe, the breeding population is estimated to number 683,000 pairs, which equates to 1,370,000 mature individuals (BirdLife International 2015). Europe forms 75-94% of the global range, so a revised estimate of the global population size is c. 1,500,000-1,800,000 mature individuals, although further validation of this estimate is needed.
The population trend is increasing in North America (based on BBS/CBC data: Butcher and Niven 2007). The European population is also estimated to be increasing (BirdLife International 2015).
This species is found on both sides of the Atlantic Ocean with small numbers of individuals reaching the equator on the western and eastern side in the south, and reaching Norway in the north. Breeding sites include northern France, the United Kingdom, Ireland, Iceland, Norway and the eastern tip Quebec (Canada) (del Hoyo et al. 1992).
This strictly marine species wanders mostly over continental selves, feeding on shoaling pelagic fish which are mostly caught by plunge-diving from large heights. It also attends trawlers and will form large congregations where food is plentiful. Breeding is highly seasonal starting between March and April, usually in large colonies on cliffs and offshore islands, but also sometimes on the mainland. Young birds will migrate to the extreme south of its range, whereas adults range less extensively but still regularly winter in the Mediterranean and Gulf of Mexico (del Hoyo et al. 1992).
The following information refers to the species's European range only: Overfishing and prey depletion is likely to affect this species, although populations in the U.K. and Ireland were not seriously affected by the Shetland sandeel stock crash in the mid 1980s (Carboneras et al. 2014). Incidental capture in fishing gear, including in longlines and purse seines also poses a threat; and the species was the most commonly caught along the Portuguese mainland coast (Oliveira et al. 2015). The species is hunted for food in some places, for example, a small annual harvest is carried out on Sula Sgeir, off north-west Scotland. The small population of northern Norway has suffered local declines and extinctions thought to be mainly due to harassment by White-tailed Eagles (Haliaeetus albicilla). The species is considered at high risk from collisions with offshore wind turbines (Bradbury et al. 2014).
Conservation Actions Underway
The species is listed on the African Eurasian Waterbird Agreement. It is covered by the EU Birds Directive as a regularly occurring migratory species. In Europe it is currently listed within 34 marine Important Bird Areas. Within the EU it is currently listed within nine Special Protection Areas.
Conservation Actions Proposed
The following information refers to the species's European range only: Identification and protection of important sites at sea. Collection of more information on individual movements to assist careful placement of offshore wind farms. On-board monitoring programmes on fishing vessels to determine the number of birds caught across the region, and implementation of bycatch mitigation measures where appropriate.
Text account compilers
Ashpole, J, Butchart, S., Calvert, R., Ekstrom, J.
BirdLife International (2017) Species factsheet: Morus bassanus. Downloaded from http://www.birdlife.org on 21/10/2017. Recommended citation for factsheets for more than one species: BirdLife International (2017) IUCN Red List for birds. Downloaded from http://www.birdlife.org on 21/10/2017.