Phalacrocorax carbo (Linnaeus, 1758)
Family: Suliformes > Phalacrocoracidae
Cormorants were once entirely coastal in habits but we have seen an increasing trend for inland breeding, a behaviour first documented here in the 1950s.
Our population is made up of birds from two different races, one of which – the continental race – is responsible for the colonisation of inland waterbodies. Cormorants make use of regular roosting sites, with some individuals remarkably faithful to these over time.
The expansion inland has brought the Cormorant into conflict with commercial fisheries and anglers, and the presence of these birds has not been welcomed by all.
Select a topic for more facts and statistics about the Cormorant
Cormorant identification is often straightforward. The following article may help when identifying Cormorant.
A black, reptilian-looking bird swims by low to the water - but is it a Cormorant or a Shag? Cormorants are more familiar and wide-spread, although Shags are more numerous. Let us help you to separate these two similar-looking species of water bird.
Listen to example recordings of the main vocalisations of Cormorant, provided by xeno-canto contributors.
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Status and Trends
Population size and trends and patterns of distribution based on BTO surveys and atlases with data collected by BTO volunteers.
This species can be found on the following statutory and conservation listings and schedules.
The Cormorant was almost exclusively a coastal breeder in the UK until 1981, but has since established colonies in many inland areas of eastern and central England (Rehfisch et al. 1999; Newson et al. 2006). Breeding had been recorded at 89 inland sites by 2012, and the inland population had risen to about 2,130 pairs by 2005 and 2,362 pairs in 2012 (Newson et al. 2007, 2013). Inland breeding in England is thought to have been sparked by birds of the continental race sinensis from the Netherlands and Denmark, although many nominate carbo from coastal colonies in Wales and England have contributed to its development.
Breeding numbers and productivity at sample colonies have been monitored annually since 1986 by JNCC's Seabird Monitoring Programme. This annual monitoring, which includes inland and coastal breeders, shows periods of temporary increase which have been followed by declines, and numbers are currently similar to those in 1986 (SMP: click here); these changes are accompanied by a long-term decrease in breeding productivity. There was a 10% increase in the UK population between full surveys in 1985-88 and 1998-2002 (JNCC 2015). Trends during 1986-2005 show decreases in Scotland and in northeast and southwest England, but no trend in Wales, and steep increases inland in England and in regions bordering the northern part of the Irish Sea (Mavor et al. 2008). The winter trend in Britain, comprising British and Irish breeders and continental visitors (Frederikson et al. 2018), showed strong increase from the late 1980s, and was stable between around 2002/03 and 2012/13 before increasing again (WeBS: Frost et al. 2020). Although the species is now green listed, both races that occur in the UK qualify for amber listing, for reasons unconnected with the UK trend.
|UK breeding population||No population change in UK (1995–2020)|
|UK winter population||+58% increase (1995/96 to 2020/21)|
Wintering Cormorants are widely distributed throughout Britain & Ireland, with highest densities along the coasts, particularly around major estuaries, and along major lowland river systems. Breeding colonies are widely distributed, including inland in Ireland and eastern England.
Occupied 10-km squares in UK
|No. occupied in breeding season||575|
|% occupied in breeding season||19|
|No. occupied in winter||2476|
|% occupied in winter||82|
European Distribution Map
Breeding Season Habitats
|Most frequent in||Estuaries|
During both winter and the breeding season there have been distribution gains, most often to low-lying inland areas.
Change in occupied 10-km squares in the UK
|% change in range in breeding season (1968–72 to 2008–11)||+41.3%|
|% change in range in winter (1981–84 to 2007–11)||+51.2%|
Cormorants are widely reported and present year-round.
Information about movement and migration based on online bird portals (e.g. BirdTrack), Ringing schemes and tracking studies.
An overview of year-round movements for the whole of Europe can be seen on the EuroBirdPortal viewer.
Lifecycle and body size information about Cormorant, including statistics on nesting, eggs and lifespan based on BTO ringing and nest recording data.
|Number of Broods||1|
|Egg Size||66×40 mm Weight = 58 g (of which 11% is shell)|
View number ringed each year in the Online Ringing Report
|Maximum Age from Ringing||21 years 6 months 21 days (set in 1984)|
|Typical Lifespan||11 years with breeding typically at 3 year|
|Juvenile Survival||0.58 (in first year)|
|Field Codes||2-letter: CA | 5-letter code: CORMO | Euring: 720|
For information in another language (where available) click on a linked name
Interpretation and scientific publications about Cormorant from BTO scientists.
Causes of change
The drivers of change for this species are unclear.
Further information on causes of change
BBS counts are very largely of immature or other non-breeding birds inland and away from breeding sites and the generally upward, then stable trend adds little to what we know about breeding numbers from the Seabird Monitoring Programme. The population growth has caused increasing conflict with fishing and aquaculture, and led to calls for the population to be controlled. Population models suggest that culling could help stabilise the population in northern Europe, but that this would not necessarily reduce conflict, and action focused on controlling damage rather than on culling would be more cost-effective (Frederiksen et al. 2001). An increase in shooting under licence in the UK since 2004 has had no detectable effect on population trends in the UK (Chamberlain et al. 2013); however the effects of unlicensed shooting are unknown.
Information about conservation actions
This species has declined at coastal colonies but has been increasing at inland colonies where many of the nesting birds are believed to be from the continental race sinensis rather than the British race carbo.
The drivers of these changes and hence potential solutions are unclear, and although the overall population is believed to have experienced recent shallow decreases, ongoing conflicts with angling and aquaculture have occurred, and hence most research relating to this species has not been aimed at conservation of Cormorants but instead has focused on this conflict and on options aimed at managing the economic impacts they cause (Kirby et al. 1996; Behrens et al. 2008). Based on their assessment of the situation in Finland, Nordberg & Salmi (2019) highlight the importance of effective engagement with stakeholders at local levels. Population models in Europe suggest that action focused on controlling damage would be more cost-effective than culling (Frederiksen et al. 2001).
Breeding performance and timing of breeding of inland and coastal breeding Cormorants Phalacrocorax carbo in England and Wales
Following the establishment of a tree-nesting colony of Great Cormorants Phalacrocorax carbo at Abberton Reservoir, Essex, in 1981, the inland breeding population in England has increased considerably
Estimating reproductive success of Great Cormorants Phalacrocorax carbo: reliability and limitations of current methodology
Cormorant control: it's not clear cut
The UK Cormorant population has increased in size and range in recent decades, with more birds breeding and wintering inland. This has led to conflicts with some fisheries, so licences have been issued to kill up to 2,000 birds annually since the mid-2000s. New research by the BTO has examined whether this control has been associated with changes in Cormorant numbers on WeBS sites, particularly on Special Protection Areas (SPAs) designated to protect species under the European Birds Directive. The study found no evidence that killing Cormorants one winter affected numbers at local sites the following winter. Cormorant population growth was associated with higher intensity control, although this does not show whether control has influenced the national population trend, as Cormorants may simply disperse as a result of disturbance. Further work is needed to monitor Cormorants outside WeBS sites and to research their population dynamics and behaviour. The key questions of whether Cormorant control has the desired effect of reducing predation at fisheries, and how cost effective it is compared to other measures, remain to be answered.
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