About Bird Ringing

Bird ringing generates information on the survival, productivity, and movements of birds, helping us to understand why populations are changing. Ringing involves catching wild birds and fitting a small metal ring to the bird’s leg. This leg ring has a unique code which allows us to identify and monitor individuals. By re-encountering individual birds that have been previously ringed, we can learn about the species that are using the site, and also their survival through time. The ringing scheme in the UK is administered by the British Trust for Ornithology (BTO), and the data gathered by ringers across the world contributes to the study of population changes and to our understanding of species declines. Ringers operate under licence administered by the BTO. At Croft Close Set Aside, we are using mist nets to capture the birds. The birds are then safely removed from the net, identified, and several measurements taken (e.g., weight and wing-length).

Methods

Ringing has taken place at the Croft Close Set Aside on four occasions between November 2021 and February 2022. Our aim is to visit the site monthly to build a year-round picture of the species that are present on site. Visit dates will depend on the weather and availability of ringers. Early visits were focused on identifying the most suitable locations for nets, bearing in mind the other users of the site and the need to minimise disturbance in the catching area. Seven different net locations have been used across the site to date – some more successfully than others.

Number of each species caught per visit date

A total of 110 birds across 13 species have been caught and processed at the Croft Close Set Aside during the first four ringing sessions. It is worth noting that these figures may include more than one encounter with the same bird if it is caught more than once. Interestingly the first bird ringed (a blue tit) at the inaugural session was also the first to be re-caught in December! There have been 102 individual birds ringed and 8 recaptures. Blue, great and long tailed tits as expected were the most numerous species, although the bird that caused the most excitement among the ringers was the female bullfinch ringed on 27 February – however the male has remained elusive to date!

For most species, it is possible to determine the year an individual bird was hatched based on the examination of the feathers. Most passerines undertake an annual moult after breeding each year, which allows these older birds to be differentiated from young birds that retain juvenile feathers. The following table shows the number of birds for each species that we have been able to age. We would expect the proportion of juvenile birds captured to increase during the breeding season as new birds fledge.