Black-throated Diver

Gavia arctica

Introduction

Although only a monochrome bird, the Black-throated Diver in summer has exquisitely patterned black, white and grey plumage.

Breeding Black-throated Divers are found in north-west Scotland and the Outer Hebrides, inhabiting large lochs preferably with small islets for nesting. In winter Black-throated Divers are present in small numbers around much of Britain and Ireland's coastal waters.

Divers have their legs and feet set well back and find movement on land very cumbersome, so their nests are always close to water.

Key Stats

Scarce

2.8kg

2-2

BTO Records

41k records

Population and distribution stats for:

No data

215 Pairs

2.8% expansion

No data

560

42.7% expansion

Identification

Curated resources to aid in the identification of Black-throated Diver

ID Videos

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

Winter Divers

Songs and Calls

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Listen to example recordings of the main vocalisations of Black-throated Diver, provided by xeno-canto contributors.

Song:

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

Amber listed

Species of European Conservation Concern

Least Concern

IUCN Red List of Threatened Species (global)

Least Concern

Schedule 1 Licence required (to disturb)*

Yes

Birds Directive Annex 1

Yes

Listed on the Annexes of*

WCA(I), WBD(I), Bern(II), Bonn(II*), AEWA

* 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)

215 Pairs (2006)

Source

BOU Category

Source

First Record*

1743

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

Population Change

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The Black-throated Diver has a small breeding population in Scotland, estimated at 215 pairs in 2006. This represents a slight increase of 16% since the previous survey in 1994, with increases occurring throughout the Scottish range (Eaton et al. 2007). A 10% range expansion has also occurred between 1988–91 and 2008–11 (Balmer et al. 2013). An assessment of environmental variables suggests there are many lakes within the range of the species that are suitable but vacant but there is insufficient historical data to assess the medium to long-term population trend (Jackson 2005) and it is therefore unclear whether the population has always been small.

Distribution

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Black-throated Divers are present round much of the coast of Britain in winter, though are virtually absent from Shetland and are scarce around northeast Scotland and Wales. The breeding distribution of Black-throated Divers is confined mainly to north and west Scotland 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

218

% occupied in breeding season

7.2%

No. occupied in winter

479

% occupied in winter

16%

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.

Winter Distribution for Black-throated Diver

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

Breeding Distribution for Black-throated Diver

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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Black-throated Diver's British breeding range has expanded 10% since the 1988–91 Breeding Atlas. Gains are concentrated in the eastern and southern parts of the range, though many of these new records refer to single birds or pairs on suitable lochs, rather than confirmed breeding events.

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)

2.8 %

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

42.7 %

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 Black-throated Diver

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

Breeding Distribution change for Black-throated Diver

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

Seasonality

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Black-throated Divers are recorded year-round, though scarce, being reported on only around 1% of complete lists.

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 Black-throated Diver 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

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 Black-throated Diver, 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

84x52 mm

Mass (% shell)

122g (9%)

Source

Clutch Size

Typical number

2-2 eggs

Observed minimum and maximum

1-3 eggs

Source

Incubation

Incubation by

Male + Female

Typical duration

30-28 days

Source

Fledging

Type of chick

Precocial, downy

Typical duration

65-60 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.

lifespan

Typical life expectancy of bird reaching breeding age

12 years with breeding typically at 3 years

Survival of adults

All adults

0.89±0.01

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 Black-throated Diver

Classification and Codes

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Order: Gaviiformes
Family: Gaviidae
Scientific name: Gavia arctica
Authority: Linnaeus, 1758

BTO 2-letter code: BV
BTO 5-letter code: BLTDI
Euring code number: 30

Alternate species names

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Catalan: calàbria agulla
Czech: potáplice severní
Danish: Sortstrubet Lom
Dutch: Parelduiker
Estonian: järvekaur
Finnish: kuikka
French: Plongeon arctique
Gaelic: Learga-dhubh

German: Prachttaucher
Hungarian: sarki búvár
Icelandic: Glitbrúsi
Irish: Lóma Artach
Italian: Strolaga mezzana
Latvian: melnkakla gargale
Lithuanian: juodakaklis naras
Norwegian: Storlom

Polish: nur czarnoszyi
Portuguese: mobelha-de-garganta-preta
Slovak: potáplica stredná
Slovenian: polarni slapnik
Spanish: Colimbo ártico
Swedish: storlom
Welsh: Trochydd Gyddfddu

Research

Interpretation and scientific publications about Black-throated Diver from BTO scientists.

Causes of Change and Solutions

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Causes of change

Analysis by Mudge & Talbot (1993) found that breeding productivity was very low and they tentatively suggested that it was too low to maintain a stable population at the time; most failures were attributed to flooding and predation. The provision of rafts to provide safe breeding sites improved breeding productivity by an estimated 44% (Hancock 2000) and hence may have contributed towards the observed recent population increases.

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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