Great Skua
Stercorarius skua (Brünnich, 1764)
NX
GRESK
5690
Family: Charadriiformes > Stercorariidae
This dark brown, large powerful seabird with obvious white wing flashes can be seen around our coasts throughout the year.
Great Skuas breed on our northern islands during the summer months but outside of the breeding season they can be seen in coastal waters anywhere in the UK. The Great Skua is a predatory seabird that will hunt small birds, rodents and Rabbits; it can also be seen chasing other seabirds in an attempt to relieve them of any food that they might have caught.
Whilst Great Skuas can be seen throughout the year most are migratory, heading to offshore West Africa. In 2022, many skuas died on their British breeding grounds in a severe outbreak of avian influenza.
Identification
Great Skua identification is often straightforward. The following article may help when identifying Great Skua.
Identifying Skuas
Identifying skuas passing offshore in late summer is one of the great challenges of bird ID. There are clues to help us, however, and - with practice - most individuals can be identified. This workshop will point you in the right direction and help you to focus on the features and markings that will be most helpful when seawatching.
Develop your bird ID skills with our training courses
Our interactive online courses are a great way to develop your bird identification skills, whether you're new to the hobby or a competent birder looking to hone your abilities.
Browse training coursesStatus and Trends
Population size and trends and patterns of distribution based on BTO surveys and atlases with data collected by BTO volunteers.
CONSERVATION STATUS
This species can be found on the following statutory and conservation listings and schedules.
POPULATION CHANGE
The population and breeding range of the Great Skua have both been increasing since 1900 (JNCC 2022). Data from Censuses suggest that numbers more than trebled between 1969–70 and Seabird 2000 (1998–2002). The subsequent trend is variable across different colonies and will not be clear until the results of the recent Seabirds Count (2015–2021) are available (JNCC 2022). An avian influenza virus affected large numbers of Great Skuas across different Scottish islands in summer 2021 (Banyard et al. 2022): the population level impacts of this outbreak are as yet unclear.
DISTRIBUTION
More than half the world population of Great Skuas is found in the UK, along the northwest seaboard of Scotland and Ireland, with highest concentrations on Shetland and Orkney, Handa, Sutherland and St Kilda.
Occupied 10-km squares in UK
No. occupied in breeding season | 162 |
% occupied in breeding season | 5.4 |
No. occupied in winter | 176 |
% occupied in winter | 5.8 |
European Distribution Map
DISTRIBUTION CHANGE
Great Skua breeding range expanded by 111% since the 1968–72 Breeding Atlas, mostly involving colonisation of new sites in the west of Scotland and in northwest Ireland since 2000.
Change in occupied 10-km squares in the UK
% change in range in breeding season (1968–72 to 2008–11) | +100% |
% change in range in winter (1981–84 to 2007–11) | +138.2% |
SEASONALITY
Great Skuas are summer visitors, arriving in March. Autumn migration of northern breeders extends into late autumn and early winter.
Movement
Information about movement and migration based on online bird portals (e.g. BirdTrack), Ringing schemes and tracking studies.
RINGING RECOVERIES
View a summary of recoveries in the Online Ringing Report.
Foreign locations of birds ringed or recovered in Britain & Ireland
Biology
Lifecycle and body size information about Great Skua, including statistics on nesting, eggs and lifespan based on BTO ringing and nest recording data.
SURVIVAL & LONGEVITY
View number ringed each year in the Online Ringing Report
Maximum Age from Ringing | 38 years 0 months 0 days (set in 2017) |
Typical Lifespan | 15 years with breeding typically at 7 year |
Adult Survival | 0.888±0.006 |
Juvenile Survival | 0.8 (in first year) |
CODES & CLASSIFICATION
Ring size | H |
Field Codes | 2-letter: NX | 5-letter code: GRESK | Euring: 5690 |
For information in another language (where available) click on a linked name
Research
Interpretation and scientific publications about Great Skua from BTO scientists.
CAUSES AND SOLUTIONS
Causes of change
Strong increases which occurred during the 1970s are believed to be associated with increases in fisheries discards; whilst the population increases have continued subsequently the rate of increase has been lower, possibly due to a reduction in discards and a reduction in sandeel abundance, though great skuas have managed to switch their diet to maintain population levels despite the changes to prey availability (Church et al. 2018). Following the population increases, density-dependent effects may now be limiting population growth in some parts of the breeding range (Meek et al. 2011). An avian influenza outbreak was detected in Great Skua colonies across different Scottish islands in summer 2021, with large numbers of birds observed with apparent symptoms of the disease and dying. The virus was confirmed in seven of the eight dead skuas which were examined (Banyard et al. 2022). It is not yet clear whether this outbreak has had population level effects.
PUBLICATIONS (2)
Contrasting effects of GPS device and harness attachment on adult survival of Lesser Black-backed Gulls Larus fuscus and Great Skuas Stercorarius skua
Modelling flight heights of Lesser Black-backed Gulls and Great Skuas from GPS: a Bayesian approach
GPS tracks and cutting edge stats shed new light on seabird flight heights
New research led by the BTO has used a combination of GPS-tracking and advanced statistics to provide new insights into seabird flight heights by night and day. This study gives important information on the risk of seabirds colliding with offshore wind turbines and at a time when governments worldwide are investing in offshore wind farms.
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