What the BTO says
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.
You do not need to belong to the BTO in order to participate in this survey
Do I need surveyors to be told if you know where Herons nest?
All the known sites where Herons currently nest are covered by surveyors. However, if you know where herons, or indeed little egrets nest, please do tell me because it might be a new site for the county. Even if you would not be able to check it a couple of times in the spring in order to work out how many nests are there (which is all that is required for a heronry survey) with any luck I might be able to find someone else to cover that site which would then be set up as a new survey site. Supplying the results to me is easy, you either fill in a card showing the dates you visited, how many occupied nests you could see and how many nests you estimated were active. The card is then sent to me and I forward it on to the BTO and also supply the results to the Surrey Bird Club. Alternatively you can now enter your results online (I am able to view the results this way too).
Do I currently need surveyors?
Not at the moment
If you know of any heron nesting sites please contact me so that I can check that this is a monitored site.