What are Recoveries and Controls?
"Recoveries" are birds ringed at Rye Meads which are subsequently reported from elsewhere, whereas "Controls" are the reverse - birds ringed elsewhere and subsequently trapped at Rye Meads.
Their importance to ornithology
Recoveries and Controls are very important in the study of birds, as they provide a much deeper insight than mere observation as to where birds are to be found at different times of year, by showing individual movements. This enables us to ascertain the importance of migration routes, stop-off and feeding locations, and wintering quarters for different populations.
There are also "Retraps", which are birds we have previously ringed and which we subsequently catch again. Whilst these don't directly help with migration data, they can help to confirm how well summer visitors are surviving in winter quarters by being caught again in a subsequent summer.
At Rye Meads, we also operate two areas as 'constant effort sites' - here we catch birds using the same net sites operated under as near as possible the same conditions year after year. This enables us to directly compare the birds caught, and the retraps, year by year, giving an indication of how populations may be fluctuating from one year to the next.
How we get this information
Each ring carries not only a unique number, but also a short address. On small rings, this is just "Brit. Mus. London SW1", but this is enough for members of the public finding a dead or injured bird to be able to send details which are forwarded to the BTO. Even from far distant countries, in Africa or western Asia, letters come reporting found rings.
The BTO acts as a clearing house for all notifications of recoveries for birds in Britain. Similarly, the national schemes of other countries will report information to the BTO, so we get to hear details of recoveries of birds we have ringed.
If you find a ringed bird, you can report it online to the BTO here.
Of course, it is the accumulated data from all ringing throughout the country, and indeed overseas, that provides enough information to begin to draw meaningful conclusions. Nevertheless, we always enjoy details of those recoveries and controls in which we play a part!