Colour Ringing as a tool for observation by Roger Skeen
Recent decades have witnessed a marked increase in the use of colour rings, flags and tags which allow individual birds to be identified without the need for re-capture. Colour-marking is particularly useful for species that can be ringed as nestlings and at Dersingham Bog we have employed that method successfully with our Stonechats.
When the ringing scheme began over 100 years ago, the primary aim was to find out more about birds’ movements. This was achieved by attaching individually marked metal rings to a bird’s leg, hoping the individual bird was recaptured either dead or alive; thus giving information on migration, longevity and population – key information in today’s ever changing bird population.
According to the BTO, analysis of data collected during a ten year study on Blackbirds in an urban Norfolk garden was undertaken to estimate seasonal and sex-specific survival rates. By following Colour-marked birds, this showed that survival rates were lowest not in winter but during early spring and were highest in autumn, and that also there was little difference between the sexes. Studies such as this are important for interpreting life-history variation and the mechanics of population change, something we wish to develop here at Dersingham.
Colour-ringing of our Stonechats has been ongoing for the past four seasons with breeding pairs increasing from three pairs up to thirteen pairs in 2016, which is revealing some interesting population dynamics. We have noted some birds returning to the same territories as previously occupied, even though similar habitat is available elsewhere. This site fidelity, although suspected, was easily confirmed with colour ring combinations.
Another interesting aspect of behaviour is that of a female Stonechat abandoning her mate after two successive failures and partnering with a successful male whose original female had gone missing. This time she successfully bred and young were fledged.
The benefits of colour-ringing allows us to follow these birds and interpret better their strategies for breeding efficiently. Further studies will hopefully allow us to gauge population growth and discover what is the optimum population size. It would certainly be interesting to follow up our ringed birds when they leave the natal area and discover if Dersingham birds are dispersing to other suitable areas.