Heronries Census


BTO published a new statement on COVID-19 on 6 July. We ask that Heronries Census volunteers follow this advice, and the specific guidance below.

England, Scotland, Wales, Northern Ireland, Bailiwicks of Guernsey & Jersey and Isle of Man: You may visit your heronry to undertake counts provided you follow the social distancing guidelines. However, you should feel under no pressure to visit your heronry if you do not feel comfortable doing so, or if you are concerned about the impacts of carrying out survey work on relations with landowners or other members of the public. Please act in the spirit of any current guidance in the country in which you are operating, and be aware of any local restrictions on travel that may be imposed at times.

Note that the recommended dates for carrying out census visits have now passed. Grey Heron chicks will already have fledged from many nests. Some Little Egret nests may still be active but some may have fledged already. If you do visit your site, therefore, please indicate in the comments box whether any Grey Heron and Little Egret estimates are considered representative for the year or are likely to be an under-estimate.

Grey Heron. Photograph by John Harding

Annual survey of all Grey Herons, Little Egrets, Cormorants and scarcer herons nesting in the UK

Heronries are the places where Grey Herons, Little Egrets and sometimes other waterbirds gather to nest. Nesting often persists for many decades at the same location and becomes very well known to birdwatchers. Grey Herons in particular are monitored efficiently and accurately by counting 'apparently occupied nests' in their heronries. The BTO's Heronries Census has gathered nest counts annually since 1928 at the UK's heronries.

The main species covered is Grey Heron but Little Egret is fully included, as are rarer species of colonial waterbirds such as Cattle Egret and Spoonbill. Nest counts of Cormorants are also collected, especially where they are nesting alongside herons. Data are shared with county recorders and for rare species with the Rare Breeding Birds Panel.

Find available sites

View available sites

You can search for available sites and make and enquiry to a local organiser prior to signing up for the Census.

Time / skill required

  • Each visit requires 10 minutes to 1 hour excluding travelling time.
  • Suitable for beginners - identify herons/cormorants and count occupied nests.
  • Survey Guidelines and Species Guide available. Further guidance and support can be requested from your Regional Organiser.

Join the project

View available sites

Project timeline, contributions & findings

Project timeline

  • Up to 3 site visits annually, in March, April and May.
  • Data to be input online by the end of August.

Contributions & findings

  • The latest Grey Heron population trends from the Heronries Census are discussed on the Grey Heron page in the BTO's BirdTrends report.
  • The modelled annual population estimates for the UK, now spanning more than 80 years, show a long-term increase.

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