Evolution in action in your back garden

At last, I've managed to grab a 'record shot' of one of the Blackcaps that is visiting my garden at the moment. Here he is, homing in on his favourite nibble - fat balls

This is a little fella that has got 'adaptation' written all over him. To see one in your garden is to see evolution in action - evolution of behaviour rather than evolution in appearance.

Fifty years ago, to find a Blackcap in Britain in winter would have been a very rare occurrence indeed.  Even here in south coast Sussex, the first sighting was not until 1947.

But numbers have gradually built up, such that you could have one wintering in a garden almost anywhere in the UK now.

And they have become particularly adept at visiting feeding stations, which is amazing because this is a little member of the warbler family that in summer hides away in woodland eating insects. But these winter birds have really taken advantage of our handouts, scoffing cut apples as well as fat.

Note how this tree-dweller much prefers to feed by clinging to a twig rather than the feeder itself - it's a good tip for where you site your feeders if you want Blackcaps to take advantage.

But this evolution I talk about is more to do with where these birds come from rather than their feeding habits. Ringing studies have shown that they aren't British-bred birds. Our summer Blackcaps winter in southern Spain and northern Africa. But our wintering birds come mostly, it is thought, from places like Germany and Belgium.

The thing is that, due to natural variation, a few birds migrate in the 'wrong' direction. Normally it doesn't pay off and they end up somewhere very unsuitable like at sea. But it seems that, 50 years ago, an 'odd' Blackcap or two flew north-west to the UK from the near-Continent instead of south-west to Spain. And they survived at our bird tables, flew back in spring, arrived on their breeding grounds nice and early, and bagged the very best spots. And all their offspring then did the same.

And so a new population built up with this new genetic predisposition - a new strain of Blackcap. And a new - and very dapper - face for us to enjoy from our windows.