Bird-ringing remains an indispensable tool

IN 1899, Hans Christian Mortensen, a Danish schoolteacher, made little rings from a sheet of aluminium and fitted them to the legs of starlings; bird-ringing had been invented.

Soon, ringing schemes were up and running in Germany, Hungary, Britain and Scandinavia. The technique, known as ‘banding’ in America, has been invaluable to bird study but, with millions of rings fitted in over a century, you might expect that little more can be learnt using it. The environment, however, is in constant flux and so are the lives of birds. Ringing remains an indispensable tool.

Responding to global warming, some species are moving closer to the poles. Black-tailed godwits, for example, used to return to their Icelandic breeding grounds in May. Now they arrive in April. Does earlier nesting affect a bird’s breeding success? Are migrants adapting successfully to new, more northerly, environments? How important is temperature at nesting sites?