Great Skua

Stercorarius skua

Introduction

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.

Key Stats

Common

1.4kg

2-2

BTO Records

69k records

Publications

Population and distribution stats for:

No data

9,650 Pairs

100% expansion

No data

No current data

138.2% expansion

Identification

Curated resources to aid in the identification of Great Skua

ID Videos

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This section features BTO training videos headlining this species, or featuring it as a potential confusion species.

Skuas

Songs and Calls

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Listen to example recordings of the main vocalisations of Great Skua, provided by xeno-canto contributors.

Call:

Flight call:

Status and Trends

Population size, trends and patterns of distribution based on BTO and partnership surveys and atlasses with data collected by BTO volunteers.

Conservation Status

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This species can be found on the following statutory and conservation listings and schedules.

UK Birds of Conservation Concern

Red listed

Species of European Conservation Concern

Least Concern

IUCN Red List of Threatened Species (global)

Least Concern

Schedule 1 Licence required (to disturb)*

Birds Directive Annex 1

Listed on the Annexes of*

Bern(III)

* A guide only. Check details with the original legislation, especially those marked with an asterisk. See About Birdfacts for more information.

Population Size

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UK (breeding)

9650 Pairs (1998-02)

Source

BOU Category

Source

First Record*

1666

* First documented occurrence. Most species undoubtedly occurred before this. See About Birdfacts for more information.

Population Change

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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

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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

These figures come from Bird Atlas 2007 and indicate how widespread a species is.

No. occupied in breeding season

162

% occupied in breeding season

5.4%

No. occupied in winter

176

% occupied in winter

5.8%

Bird Atlas distribution maps show where bird species breed or winter in Britain and Ireland. For breeding maps, larger dots indicate higher certainty the species bred in that area.

Click the map to enlarge,
or view it on Bird Atlas Mapstore.

Click the map to enlarge,
or view it on Bird Atlas Mapstore.

To view and download up-to-date distribution information aggregated from across BTO and partnership surveys and schemes, see our data holdings on the NBN Atlas.

European Distribution Map

European Breeding Bird Atlas 2

Distribution Change

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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

These figures come from Bird Atlas 2007-11 and indicate by how much occupied areas have expanded or contracted over recent decades.

% change in range in breeding season (1968–72 to 2008–11)

100 %

% change in range in winter (1981–84 to 2007–11)

138.2 %

Bird Atlas distribution change maps show how bird distributions have changed through time. Coloured upward-pointing triangles show places apparently colonised over the period; grey downward-pointing triangles show places apparently vacated. Shading show places occupied.

Winter Distribution change for Great Skua

Click the map to enlarge,
or view it on Bird Atlas Mapstore.

Breeding Distribution change for Great Skua

Click the map to enlarge,
or view it on Bird Atlas Mapstore.

Seasonality

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Great Skuas are summer visitors, arriving in March. Autumn migration of northern breeders extends into late autumn and early winter.

Weekly pattern of occurrence

The graph shows when the species is present in the UK, with taller bars indicating a higher likelihood of encountering the species in appropriate regions and habitats.

Phenology graph — Weekly occurrence patterns (shaded cells and reporting rates (vertical bars) based on BirdTrack data. Reporting rates give the likelihood of encountering the species each week.

Movement

Information about Great Skua movements and migration based on online bird portals (e.g. BirdTrack), Ringing schemes and tracking studies.

Britain & Ireland movement

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View a summary of recoveries in the Online Ringing Report

Foreign locations of birds ringed or recovered in Britain & Ireland

Dots show the foreign destinations of birds ringed in Britain & Ireland, and the origins of birds ringed overseas that were subsequently recaptured, resighted or found dead in Britain & Ireland. Dot colours indicate the time of year that the species was present at the location.

Winter (Nov-Feb)
Spring (Mar-Apr)
Summer (May-Jul)
Autumn (Aug-Oct)

Foreign locations of birds ringed or recovered in Britain & Ireland

European movements

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EuroBirdPortal uses birdwatcher's records, such as those logged in BirdTrack to map the flows of birds as they arrive and depart Europe. See maps for this species here.

The Eurasian-African Migration Atlas shows movements of individual birds ringed or recovered in Europe. See maps for this species here.

Biology

Lifecycle and body size information for Great Skua, including statistics on nesting, eggs and lifespan based on BTO ringing and nest recording data.

Productivity and Nesting

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Nesting timing

Typical (exceptional) number of broods

Source

Egg measurements

Typical length x width

70x50 mm

Mass (% shell)

91g (7%)

Source

Clutch Size

Typical number

2-2 eggs

Observed minimum and maximum

1-2 eggs

Source

Incubation

Incubation by

Male + Female

Typical duration

32-26 days

Source

Fledging

Type of chick

Altricial, downy

Typical duration

51-40 days

Source

Survival and Longevity

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Survival is shown as the proportion of birds surviving from one year to the next and is derived from bird ringing data. It can also be used to estimate how long birds typically live.

View number ringed each year in the Online Ringing Report.

lifespan

Typical life expectancy of bird reaching breeding age

15 years with breeding typically at 7 years

Source

Maximum age from a ringed bird

38 years, (set in 2017)

Source

Survival of adults

All adults

0.888±0.006

Source

Survival of juveniles

All juveniles

0.8 (in first year)

Source

Biometrics

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Wing length and body weights are from live birds (source).

Ring Size

Classification, names and codes

Taxonomy, names and species codes for Great Skua

Classification and Codes

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Order: Charadriiformes
Family: Stercorariidae
Scientific name: Stercorarius skua
Authority: Brünnich, 1764

BTO 2-letter code: NX
BTO 5-letter code: GRESK
Euring code number: 5690

Alternate species names

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Catalan: paràsit boreal
Czech: chaluha velká
Danish: Storkjove
Dutch: Grote Jager
Estonian: suuränn
Finnish: isokihu
French: Grand Labbe
Gaelic: Fàsgadair-mòr

German: Skua
Hungarian: nagy halfarkas
Icelandic: Skúmur
Irish: Meirleach Mór
Italian: Stercorario maggiore
Latvian: liela klijkaija
Lithuanian: didysis plešikas
Norwegian: Storjo

Polish: wydrzyk wielki
Portuguese: mandrião-grande / alcaide
Slovak: pomorník velký
Slovenian: velika govnacka
Spanish: Págalo grande
Swedish: storlabb
Welsh: Sgiwen Fawr

English folkname(s): Bonxie

Research

Interpretation and scientific publications about Great Skua from BTO scientists.

Causes of Change and Solutions

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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 (5)

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The status of the UK’s breeding seabirds

Five seabird species are added to the Birds of Conservation Concern Red List in this addendum to the 2021 update, bringing the total number of Red-listed seabird species to 10, up from six since seabirds were last assessed. The Amber List of seabirds moves from 19 to 14 species, and the Green List increases from one to two species.

29.09.24

Papers

View on journal website

Seabird Population Trends and Causes of Change: 1986–2023

This report presents the latest seabird population trends in breeding abundance and productivity using data from the Seabird Monitoring Programme (SMP).The report documents changes in the abundance and productivity of breeding seabird species in Britain and Ireland from 1986 to 2023, and provides a detailed account of the 2021, 2022 and 2023 breeding seasons.This report includes both inland and coastal populations and trends from the Channel Islands, England, Isle of Man, Northern Ireland, Scotland, Wales and the Republic of Ireland, which are presented where sufficient data are available. The results from this report are used more broadly to assess the health of the wider environment, to inform policy and for conservation action.

21.11.24

Reports Research reports

Read the report View Online

Impacts of highly pathogenic avian influenza on seabird populations in the North Sea are detectable in sea-watchers’ migration counts

BTO research reveals that seabird population declines due to Highly Pathogenic Avian Influenza (HPAI) can be detected using data collected by volunteer seawatchers.

28.12.24

Papers

View on journal website

Modelling flight heights of Lesser Black-backed Gulls and Great Skuas from GPS: a Bayesian approach

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.

03.08.16

Papers

Contrasting effects of GPS device and harness attachment on adult survival of Lesser Black-backed Gulls Larus fuscus and Great Skuas Stercorarius skua

22.03.16

Papers

More Evidence

More evidence from Conservation Evidence.com

Partners

Birdfacts is based on data collected by volunteers participating in surveys that are organised and funded by BTO, RSPB, Esmée Fairbairn Foundation, JNCC and other partners.

BTO

Esmée Fairbairn Foundation

JNCC

RSPB

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