Press Releases - July/Aug 2005 - Item 9

No. 2005/08/26
31 August 2005

Controlling Cormorants Carefully

Following a ministerial statement and a scientific assessment, the Government is issuing up to 3000 licences per year for the control of Cormorants in England and Wales, but what are the implications for our native subspecies?

Two forms of Cormorant (Phalacrocorax carbo) occur in the UK, the continental sinensis (which breeds mainly in Europe but many of which winter here) and the native carbo. Whilst the two subspecies look quite similar, genetic work has shown that they are as genetically distinct as Carrion and Hooded Crows, forms that are now recognised as separate species. Whilst the inland tree-nesting sinensis has increased in numbers, heralding the calls for control, the cliff-nesting carbo, like many seabirds in the UK, has experienced a decrease in numbers. The effect of the proposed cull on the two different forms is currently unknown.

Stuart Newson, BTO Population Biologist said: “We know that the number of birds breeding at many traditional coastal colonies are in long-term decline and it is vital that we have a reliable census of wintering and breeding numbers, against which any change can be monitored.”

The only long-term data available for wintering Cormorants comes from the Wetland Bird Survey (WeBS) where an unknown proportion of Cormorant wintering sites are counted each year. These counts have been used to develop population models to assess the impact of the proposed cull. These models suggest that the overall Cormorant population will not be adversely affected by these measures. However, there has been no distinction between the two forms in the computer models. A comprehensive survey is needed before the effect of the control measures on our native carbo can be ascertained.

Stuart adds “Preliminary investigation has shown that controlling the inland sinensis population is unlikely to reduce their numbers, whereas controlling our native carbo Cormorants may lead to a major decline in their breeding population.”

Traditionally, Cormorants are coastal breeders on cliffs and islands with just under 3000 pairs in England and Wales. However, since 1981 inland tree nesting has been seen in England and there are now several colonies comprising some 1,500 pairs mostly of the continental sinensis form.

Sadly for our native coastal birds, some of which move inland for the winter, it is very difficult to tell the difference between the two forms in the field. Even researchers working on Cormorants cannot ascribe all individuals to a specific race. This added problem makes it virtually impossible to selectively control continental birds and so we need a proper understanding of the numbers and distribution of both forms across the UK.

Notes for Editors

1) The Wetland Bird Survey (WeBS) is funded by a partnership of the British Trust for Ornithology, the Wildfowl and Wetlands Trust, the Royal Society for the Protection of Birds and the Joint Nature Conservation Committee (on behalf of Natural England, Scottish Natural Heritage and the Countryside Council for Wales, and also on behalf of the Environment and Heritage Service in Northern Ireland).

2) Cormorant Facts. Surprisingly, their plumage is not waterproof, so they often stand on rocks, wings out-stretched to dry off after fishing. Cormorants lay 3-4 eggs and both the male and female incubate them for almost a month. Cormorants start breeding when they are 3 years old and typically live for 6 years. The oldest Cormorant recorded was 26 years, 6 months. Breeding performance is higher at inland colonies than at coastal colonies, mainly due to the higher survival of chicks.

3) Cormorants are an amber listed Species of Conservation Concern given that >50% of the UK breeding population is located at just 10 sites. This puts them in the same category as the Osprey and Barn Owl.

4) Images of Cormorants are freely available for use in association with this press release. Please contact

5) The BTO has an ISDN line available for radio interviews.

For further information contact:

Martin Fowlie on 01842 750050 (office hours) Email
Stuart Newson on 01842 750050 (office hours)

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