Heronries Census

Important Notice re Covid 19

In view of the current restrictions Please do not leave your home to carry out this survey

An Ongoing Annual Survey

The longest running BTO survey, 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.

If you are not very experienced, and want to start off with a relatively straightforward survey, then this survey might be the one for you. 

You do not need to belong to the BTO in order to participate in this survey.

The Time of Year for the survey

Spring.

Grey Heron, by Liz Cutting / BTO

What the survey involves

Visiting a known heronry on more than one occasion during the breeding season and working out how many nests are occupied.  Depending on the size of the heronry this might take between 10 or 60 minutes (excluding travelling time).

When do you do it?

February or March to check out if the Heronry has survived the winter gales.  Nests should be counted in the second half of April, with this count being supplemented (if possible) by an earlier and a later visit. You can visit a heronry at any time of day, although the birds may be more active in the morning.  A visit in May should pick up other species nesting such as Little Egret or Cormorant.  

More information on why this survey is being run

As top predators in the freshwater food chain, herons are able to thrive only when their potential prey are also present in good numbers. Monitoring their breeding population sizes can therefore provide a valuable indicator of the health of the freshwater environment.

Counting nests provides by far the most efficient and accurate measure of breeding numbers for most colonial birds. For this reason, BTO monitors colonial herons through special surveys that collate counts of “apparently occupied nests” at colonies.

The BTO Heronries Census collects nest counts of herons from as many heronries as possible in the UK each year. The main species covered is Grey Heron but Little Egret is fully included, as are rarer species of colonial herons such as Cattle Egrets (which nested in the UK for the first time in 2008). 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.

In Surrey the 2007-2012 Atlas showed a reduction in breeding for Grey Heron. Here are the results.

What skills are required?

You need to be able to identify Grey Heron, Little Egret and Cormorant.

You do not need access to the internet as forms are available but most surveyors enter their results online.

Where are the survey sites in Surrey?

There are 16 active known sites in Surrey. Here is a list of all the sites in Surrey (whether covered or not) and here is a list of the sites in Surrey that need covering.  Can you help with one of these sites?

How do I get involved?

If you are interested in helping with the survey or would like more information please contact the Regional Organiser (RO) for this survey.  The RO is Ray Phillips email ray@btosurrey.co.uk