Arctic Skua

Stercorarius parasiticus

Introduction

This highly-migratory seabird has a fast and powerful flight that can also be nimble and manoeuvrable. It breeds on moorland in the Arctic but spends most of its year in the open ocean.

A few colonies are found in the far north and west of Britain, on moorland within easy reach of the sea. Elsewhere, Arctic Skuas occur offshore on migration and may be seen close inshore, often when chasing terns.

Seabird censuses reveal that Arctic Skuas breeding in Britain are currently in severe decline. Recent tracking studies have shown that breeding birds make long excursions to gather food for their chicks, perhaps indicating that suitable prey is scarce near the colonies.

Key Stats

Common

416.4g

2-2

BTO Records

75k records

Publications

Population and distribution stats for:

No data

785 Pairs

7.1% expansion

No data

No current data

61% expansion

Identification

Curated resources to aid in the identification of Arctic 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 Arctic 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

Endangered

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)

785 Pairs (2015)

Source

BOU Category

Source

First Record*

1713

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

Population Change

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With the UK the Arctic Skua is restricted to north and west Scotland. Based on previous Censuses, the population increased substantially between 1969–70 and 1985–88; despite a subsequent decline, breeding numbers counted by Seabird 2000 (1998–2002) remained approximately double the 1969–70 population. The results of the recent Seabirds Count (2015–2021) are not yet available; however, annual monitoring data suggest that the decline has continued (JNCC 2022). Perkins et al. (2018) found that numbers had declined by 81% between 1992 and 2015 within their core Scottish breeding areas. The effects of the ongoing highly pathogenic avian influenza (HPAI) outbreak are being closely monitored.

Distribution

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Arctic Skuas breeding in the UK are at the southwestern extremity of their mostly circumpolar breeding range. In the UK they nest in the Northern Isles, Caithness and Sutherland, the Outer Hebrides, St Kilda and a few southern Inner Hebridean islands. Highest numbers are found on Shetland, Orkney and the Outer Hebrides.

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

119

% occupied in breeding season

3.9%

No. occupied in winter

108

% occupied in winter

3.6%

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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Arctic Skuas have declined significantly and this is beginning to show in the range maps, with losses in the southern part of the range on Islay and Jura.

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)

7.1 %

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

61 %

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 Arctic Skua

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

Breeding Distribution change for Arctic Skua

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

Seasonality

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Arctic Skuas are predominantly summer visitors, arriving from April. Peak reporting is during autumn passage in August and September. Occasional birds may 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 Arctic 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 Arctic 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

58x40 mm

Mass (% shell)

48g (6%)

Source

Clutch Size

Typical number

2-2 eggs

Observed minimum and maximum

1-3 eggs

Source

Incubation

Incubation by

Male + Female

Typical duration

28-25 days

Source

Fledging

Type of chick

Altricial, downy

Typical duration

30-25 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

12 years with breeding typically at 4 years

Source

Maximum age from a ringed bird

25 years, 10 months, 24 days (set in 2003)

Source

Survival of adults

All adults

0.886

Source

Survival of juveniles

All juveniles

0.68 (in first year)

Source

Biometrics

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

Wing length

Average ±1 std deviation; range and sample size in brackets.

All adults

328.9±8.3 mm

(314-343 mm, N=35)

Body weight

Average ±1 std deviation; range and sample size in brackets.

All adults

328.9±8.3 mm

(314-343 mm, N=35)

Ring Size

Classification, names and codes

Taxonomy, names and species codes for Arctic Skua

Classification and Codes

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Order: Charadriiformes
Family: Stercorariidae
Scientific name: Stercorarius parasiticus
Authority: Linnaeus, 1758

BTO 2-letter code: AC
BTO 5-letter code: ARCSK
Euring code number: 5670

Alternate species names

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Catalan: paràsit cuapunxegut
Czech: chaluha príživná
Danish: Almindelig Kjove
Dutch: Kleine Jager
Estonian: söödikänn
Finnish: merikihu
French: Labbe parasite
Gaelic: Fàsgadair

German: Schmarotzerraubmöwe
Hungarian: ékfarkú halfarkas
Icelandic: Kjói
Irish: Meirleach Artach
Italian: Labbo
Latvian: isastes klijkaija
Lithuanian: smailiauodegis plešikas
Norwegian: Tyvjo

Polish: wydrzyk ostrosterny
Portuguese: mandrião-parasítico / moleiro-pequeno
Slovak: pomorník príživný
Slovenian: bodicasta govnacka
Spanish: Págalo parásito
Swedish: kustlabb
Welsh: Sgiwen y Gogledd

Research

Interpretation and scientific publications about Arctic Skua from BTO scientists.

Causes of Change and Solutions

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Causes of change

The decline in the Arctic Skua population is believed to be driven by strong decreases in breeding productivity (Perkins et al. 2018), with complete breeding failure occurring more frequently (JNCC 2022). Arctic Skuas are kleptoparasites, stealing food from other seabirds such as Kittwakes and auks. Recent declines for these species have been linked to the decline in their prey species, in particular sandeels Ammodytes marinus and it is likely that this will also have affected Arctic Skua productivity (Dwason et al. 2011; Perkins et al. 2018). Productivity is also likely to have been impacted by increases in the Great Skua population, through increased predation of Arctic Skua chicks (Meek et al. 2011; Perkins et al. 2018) and also through competition for territories (Dawson et al. 2011) and food (Meek et al. 2011).

Publications (6)

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New insights into the migration and wintering areas of Scottish-breeding Arctic Skuas

Research by BTO Scotland unveils the migration routes and wintering grounds of one of the Arctic Skua, one the UK’s rarest and most endangered seabirds.

29.09.24

Papers

View on journal website

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

Atlantic populations of a declining oceanic seabird have complex migrations and weak migratory connectivity to staging areas

Tracking the long-distance migrations of Arctic Skuas from their north-east Atlantic breeding grounds revealed complex migration strategies, with mixing of individuals from different populations at important staging areas before the birds reached their southern wintering grounds.  

07.03.24

Papers

Read online

The risk of extinction for birds in Great Britain

The UK has lost seven species of breeding birds in the last 200 years. Conservation efforts to prevent this from happening to other species, both in the UK and around the world, are guided by species’ priorities lists, which are often informed by data on range, population size and the degree of decline or increase in numbers. These are the sorts of data that BTO collects through its core surveys.

01.09.17

Papers

Sex-specific food provisioning in a monomorphic seabird, the common guillemot Uria aalge: nest defence, foraging efficiency or parental effort?

01.01.09

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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