International Swan Census

abundance_isc_whooperswansPrior to 1995, censuses of the Northwest European Bewick’s Swan Cygnus columbianus bewickii and the Iceland Whooper Swan Cygnus cygnus populations were coordinated separately. Bewick’s Swan censuses took place across Europe in January 1984, 1987 and 1990, whilst the first complete census of the Whooper Swan population, covering Britain, Ireland and Iceland, was undertaken in January 1986, with a second in January 1991. In January 1995, the Wetlands International / IUCN SSC Swan Specialist Group combined the two censuses and since then the International Swan Census (ISC) has been undertaken every five years.

Aim and methods

The main aim of the ISC is to estimate the size and distribution of each population, as well as identify important wintering sites. Age assessments are also made during the surveys, providing a coordinated estimation of breeding success. In addition counters are asked to record the type of habitat used by the swans during the census. These data are analysed to assess whether there has been any major shift in habitat use over time.

The ISC involves one co-ordinated site-based survey timed to coincide with the International Waterbird Census. In the UK, the census also coincides with the Wetland Bird Survey (WeBS) Core Count, since this gives good general coverage. Counts at sites not covered through WeBS provide a more complete survey. Though the majority of counts are made on the ground, a number of sites in Ireland and Iceland are covered from the air due to difficulty in access.


Results from the International Swan Census have been presented in various reports and papers. Please see our ‘Reports and newsletter‘ page. Summary results are also presented on the species account pages for the Whooper Swan and the Bewick’s Swan.

Getting involved

The most recent census took place in January 2020. The next census is due to take place in 2025.

To participate in the International Swan Census an observer needs to be confident that they can identify Bewick’s and Whooper Swans and also have some experience of counting birds.

The census is undertaken at five-yearly intervals and each survey requires one count on a pre-determined date, usually in January. The census covers sites throughout Britain and Ireland.


The overall coordination of the census is by the Wetlands International /  IUCN SSC Swan Specialist Group. In Britain, Ireland and Iceland the census is organised by WWT, the Irish Whooper Swan Study Group and the following partners:

Swan Specialist Group 

BirdWatch Ireland logo

BirdWatch Ireland

IINH logo

Icelandic Institute of Natural History

ISPB logo

BirdLife Iceland