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Catharacta Skua -- (Brünnich, 1764)

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Catharacta Skua -- (Brünnich, 1764) Catharacta skua -- (Brünnich, 1764) ANIMALIA -- CHORDATA -- AVES -- CHARADRIIFORMES -- STERCORARIIDAE Common names: Great Skua; Grand Labbe European Red List Assessment European Red List Status LC -- Least Concern, (IUCN version 3.1) Assessment Information Year published: 2015 Date assessed: 2015-03-31 Assessor(s): BirdLife International Reviewer(s): Symes, A. Compiler(s): Ashpole, J., Burfield, I., Ieronymidou, C., Pople, R., Tarzia, M., Wheatley, H. & Wright, L. Assessment Rationale European regional assessment: Least Concern (LC) EU27 regional assessment: Least Concern (LC) In Europe, although this species may have a small range, it is not believed to approach the thresholds for Vulnerable under the range size criterion (Extent of Occurrence 10% in ten years or three generations, or with a specified population structure). The population trend is not known, but the population is not believed to be decreasing sufficiently rapidly to approach the thresholds under the population trend criterion (30% decline over ten years or three generations). For these reasons the species is evaluated as Least Concern in Europe. Within the EU27, although this species may have a small range, it is not believed to approach the thresholds for Vulnerable under the range size criterion (Extent of Occurrence 10% in ten years or three generations, or with a specified population structure). 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). For these reasons the species is evaluated as Least Concern in the EU27. Occurrence Countries/Territories of Occurrence Native: Austria; Belgium; Bulgaria; Denmark; Faroe Islands (to DK); Greenland (to DK); France; Germany; Iceland; Ireland, Rep. of; Italy; Netherlands; Norway; Svalbard and Jan Mayen (to NO); Portugal; Russian Federation; Slovakia; Spain; Sweden; United Kingdom; Gibraltar (to UK) Origin Uncertain: Cyprus Vagrant: Croatia; Czech Republic; Finland; Greece; Hungary; Latvia; Lithuania; Luxembourg; Malta; Montenegro; Poland; Romania; Serbia; Slovenia; Switzerland; Turkey Population The European population is estimated at 16,300-17,200 pairs, which equates to 32,600-34,500 mature individuals. The population in the EU27 is estimated at 9,600 pairs, which equates to 19,200 mature individuals. For details of national estimates, see Supplementary PDF. Trend In Europe the population size trend is unknown. In the EU27 the population size is estimated to be increasing. For details of national estimates, see Supplementary PDF. Habitats and Ecology This marine species avoids land during migration and winter, aggregating in winter in areas where it can scavenge from fisheries. It breeds on islands, usually avoiding areas frequented by humans and favours flat ground with some vegetation cover, but less than 20 cm tall. Breeding begins in May and it is loosely colonial but highly territorial. The nest is a scrape typically lined with dead grass. Clutches are normally two eggs, but inexperienced birds may only lay one. It has a hugely varied diet owing to being a highly opportunistic feeder. Individuals regularly show individual specialisations in diet and feeding with some colony-specific learning. The species is migratory; wintering mostly off the coast of Iberia but younger birds will travel further (Furness 1996). Habitats & Altitude Habitat (level 1 - level 2) Importance Occurrence Grassland - Tundra major breeding Marine Neritic - Macroalgal/Kelp suitable breeding Marine Neritic - Macroalgal/Kelp suitable non-breeding Marine Neritic - Pelagic major breeding Marine Neritic - Pelagic major non-breeding Marine Neritic - Seagrass (Submerged) suitable breeding Marine Neritic - Seagrass (Submerged) suitable non-breeding Marine Neritic - Subtidal Loose Rock/pebble/gravel suitable breeding Marine Neritic - Subtidal Loose Rock/pebble/gravel suitable non-breeding Marine Neritic - Subtidal Rock and Rocky Reefs suitable breeding Marine Neritic - Subtidal Rock and Rocky Reefs suitable non-breeding Marine Neritic - Subtidal Sandy suitable breeding Marine Neritic - Subtidal Sandy suitable non-breeding Marine Neritic - Subtidal Sandy-Mud suitable breeding Marine Neritic - Subtidal Sandy-Mud suitable non-breeding Marine Oceanic - Epipelagic (m) suitable non-breeding Altitude Occasional altitudinal limits Threats Declines in Shetland have been due to a recent reduction in sand eel stocks that have resulted in reduced breeding success and less birds at the largest colonies. Changes in fishing practices could also have serious impacts as more than half the summer diet at Shetland is made up of discards from fisheries (Furness 1996) and when discard rates are reduced this species will switch to predating other birds, especially if small shoaling pelagic fish are scarce (Votier et al. 2004). Fishing activities also pose a threat through drowning in fishing nets or being caught on hooks. Human persecution (often illegal) has limited the size of some colonies although harvesting for food has now nearly ceased (Furness 1996). The species is also affected by climate change (Oswald et al. 2008). Threats & Impacts Threat (level 1) Threat (level 2) Impact and Stresses Biological resource Fishing & harvesting Timing Scope Severity Impact use aquatic resources Ongoing Majority (50-90%) Slow, Significant Medium Impact (unintentional Declines effects: (large scale) [harvest]) Stresses Indirect ecosystem effects Biological resource Hunting & trapping Timing Scope Severity Impact use terrestrial animals Ongoing Minority (<50%) Slow, Significant Low Impact (intentional use - Declines species is the target) Stresses Species mortality Climate change & Habitat shifting & Timing Scope Severity Impact severe weather alteration Ongoing Unknown Unknown Unknown Stresses Ecosystem degradation; Indirect ecosystem effects Conservation Conservation Actions Underway There are currently no known significant conservation measures for this species. Conservation Actions Proposed As it is not desirable to maintain current rates of fish discard, conservation measures are needed to conserve sandeel stocks in order to provide an alternative food source for this species and avoid a switch to preying on other bird species, which may impact populations of other seabirds (Votier et al. 2004). Bibliography Furness, R.W. 1996. Great Skua (Catharacta skua). In: del Hoyo, J., Elliott, A., Sargatal, J., Christie, D.A. and de Juana, E. (eds.) 2014. Handbook of the Birds of the World Alive. Lynx Edicions, Barcelona. (retrieved from http://www.hbw.com/node/53957 on 7 April 2015). Oswald, S.A., Bearhop, S., Furness, R.W., Huntley, B. and Hamer, K.C. 2008. Heat stress in a high‐latitude seabird: effects of temperature and food supply on bathing and nest attendance of great skuas Catharacta skua . Journal of Avian Biology 39(2): 163-169. Votier, S.C., Furness, R.W., Bearhop, S., Crane, J.E., Caldow, R.W., Catry, P., Ensor, K., Hamer, K.C., Hudson, A.V., Kalmbach, E., Klomp, N.I., Pfeiffer, S., Phillips, R.A., Prieto, I. and Thompson, D.R. 2004. Changes in fisheries discard rates and seabird communities. Nature 427(6976): 727-730. Map (see overleaf) .
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