International Swan Census

International Swan Census

Information about the International Swan Census (ISC), including the background to the survey and how to take part. Please note: the next census takes place on the weekend of 17-18 January 2026. 

About the International Swan Census

The International Swan Census (ISC) estimates the size and distribution of Whooper and Bewick’s Swan populations in the UK and the Republic of Ireland. 

Numbers of these species are monitored annually through the Wetland Bird Survey (WeBS) and the Irish Wetland Bird Survey (I-WeBS). These schemes provide good coverage of a high proportion of wintering sites used by Whooper Swans, but do not survey a number of non-wetland or temporally flooded areas. Because of this, a more comprehensive census that focuses specifically on these swan species is required to fully assess the size of their populations. 

The ISC is carried out every six years (formerly every five years). In addition to gathering data about the population sizes and distributions, the census also: 

  • Identifies important wintering sites for both Whooper and Bewick’s Swan;
  • Conducts age assessments to provide a coordinated estimation of breeding success;
  • Records the type of habitat used by the swans during the census to assess whether there has been any major shift in habitat use over time.

When is the International Swan Census?

  • The next census takes place on the weekend of 17-18 January 2026. 

These dates coincide with the WeBS Core Count dates and coordinate with the International Waterbird Census. 

What does an ISC survey entail?

The ISC involves one coordinated site-based survey timed to coincide with the International Waterbird Census. In the UK, the census also coincides with the WeBS Core Count since this gives good general coverage. 

Surveyors need to: 

  • Count all Whooper and Bewick’s Swans seen at their site;
  • Record age assessments (the number of adults and juveniles);
  • Record the habitat type used by the swans.

When to Count

While most sites can be counted at any time of the day, both Whooper and Bewick's Swans will often roost on waterbodies but then depart these sites very early in the morning to head to arable land, often some way from where they roost, to spend the day feeding and then return at dusk. If the ISC site you will be counting is known to hold roosting swans, these sites should be counted either at first light before the swans leave or at dusk to count birds coming into roost, though birds may arrive after dark so morning would be preferable. If your site is used at different times of day you can submit both a roost count (for overall numbers) and a daytime count (for habitat and age information of those staying on site) either in GSMP Online, or via WeBS Online (using the casual/roost counts data entry option for a visit solely to count roosting swans).

If you come across swans feeding in fields, these can be recorded in GSMP Online and on your submission please note if you know where these birds roost to allow us to account for potential double counting.

How do I get involved?

If you'd like to take part in the ISC, you will need to find a vacant site to survey and register your interest for that site. Once the site has been confirmed, you need to formally register with the survey. 

Find an ISC site to count

The census covers all wetland sites in Britain and Ireland that are monitored through WeBS, as well as any additional sites where wintering Whooper Swans and/or Bewick’s Swans are currently known or have been known to utilise. These include areas such as agricultural land and flooded fields. You can view available sites on the vacant ISC site map.

Register your interest in a site

Once you have found a vacant square, you can register your interest in surveying it via the vacant ISC site map:

  1. Select a vacant site on the map.
  2. Complete the form for the vacant site. This will send an email to the ISC Local Organiser for that region.
  3. The Local Organiser will get in touch to talk to you about the survey and sites available before allocating a site to you.

Existing WeBS Counters can request their WeBS site and may carry out the census as part of their monthly WeBS count - please note that you are the WeBS Counter when you request the site.

Register with the GSMP Online Portal

  • This step is not necessary for WeBS counters who are planning to carry out the census as part of their monthly WeBS count.
  • If you are a WeBS counter and you plan to carry out the census at a site other than your usual WeBS site, you will need to complete these steps. 

Once you have been allocated a site, you will need to register with 'GSMP Online'. This is an online portal where you view and enter your survey data, and access lots of helpful resources. 

Existing WeBS counters can enter their counts into WeBS Online, and if any of the target swans are recorded, they will be offered the chance to add their counts to the ISC along with any additional age and habitat information.

If you already have a MyBTO account:

  • Log in to MyBTO
  • Then look for the Goose & Swan Monitoring Programme under "Sign Up for Projects" and click "Register".

If you don't have a MyBTO account:

Resources

Health and Safety

BTO provides Health and Safety information for volunteers, which we recommend you read before starting your surveys.

Submitting your ISC records

Please see our guide to using GSMP online for help with entering your counts. You can also watch the video below:

Although GSMP Online is the easiest and most convenient way to send your data to us, a recording form is available to download for you to print and send to us.


 

Scroll down