The British and Irish Ringing Scheme is organised by the British Trust for Ornithology (https://www.bto.org/). Ringing produces valuable data that helps us understand and protect birds. Research into survival rates, migration patterns, health of populations, morphology and life history traits can all be informed through ringing.
Birds are caught as they fly into mist nets that are set-up temporarily. The birds lie unharmed in the nets until they are extracted by skilled ringers. A small metal ring is fitted to new birds and a set of measurements (eg. weight and wing length) are made of the bird before it is released.
More information about ringing can be found on the BTO website:-
Bird Ringing at Treswell
Spearheaded by John McMeeking, ringing in the wood commenced in December 1972. A throughout-the-year, constant-effort programme was subsequently developed and has run continuously from 1978. Seven ‘standard sites’ are each visited five times a year. At each visit 10 mist nets of total length 180 meters are set. These nets are always set in exactly same location each time. Additional nets may be set during visits in non-standard places according to opportunity. Every net location is recorded to a resolution of 60 metres.
Treswell Wood enjoys a very high recapture rate of its ringed birds. Recaptures are particularly valuable: indeed the whole purpose of ringing is to be able to follow the lives of individual birds. Each recapture tells us more about the bird's survival and movement (or, very often, extremely sedentary behaviour). Recaptures are also vital in helping to improve knowledge of ageing and sexing techniques. By looking at the history of recaptured birds we can check that we are ageing adults as adult and determining sex consistently. But there are always some birds which have display aberrant features: the Great Spotted Woodpecker captured with 'two unmoulted, red-tipped, juvenile crown feathers' had, in fact, been ringed 10 years previously. Ringers (even experienced ones) beware.