About the census

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.

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.

Taking part

If you would like to take part, you can find a heronry to monitor at an available heronry site. You can search for available sites and make and enquiry to a local organiser prior to signing up for the Heronries Census.

• View available sites

Code of Conduct

Volunteers must follow BTO’s Code of Conduct. This code applies to our staff, our members, and volunteers, including surveyors and participants in the Ringing and Nest Record Schemes, (hereafter referred to collectively as ‘staff and supporters’). It applies to all BTO activities, whether online (including meetings and events, telephone, letter, and email) or offline (any face-to-face interaction). We've also written some guidance for volunteer fieldworkers, which will help beginners in particular.