14Ingham’s Daily Express W RLD
THERE is a tree a short walk from my home where every year I mark the beginning of spring. The herald is a small, sparrowsized bird which makes up for his drab appearance with a beautiful song. The chorister is a blackcap, a warbler that spends its winters around the Mediterranean. Every spring about 1.6 million pairs flock here to grace our woods and gardens with their song and chick-rearing.
Well, blackcaps are evolving – before our eyes. Our breeding birds still go south for the winter but they are replaced in the colder months by another group of up to 25,000 blackcaps which have turned migration on its head.
These birds are from central Europe, Austria, Germany and France. When the days get shorter, they spurn the south and fly northwest to Britain and Ireland.
They are not only changing their behaviour but also their anatomy, says the British Trust for Ornithology, Oxford University and the Max Planck Institute in the journal Global Change Biology. They found blackcaps are thriving here thanks to milder winters and food – such as fatballs and sunflower hearts – left out by birdlovers.
The blackcaps’ cousins wintering in the Med – large numbers from central Europe still fly south in the autumn, like our breeders – mainly eat fruit while soaking up the sun.They forage the landscape, whereas our refugees move around less because they know where our garden feeders are.
This is even affecting their body shape. Adult blackcaps wintering in gardens are slimmer because they do not need to build body fat in case of food shortages. This makes them more agile and better able to dodge predators such as cats and sparrowhawks.
But just before migrating back to, say, Bavaria or the Tirol, they can fatten up very quickly thanks to the human handouts.
Britain is also closer to Central Europe than, say, North Africa, so our birds get back about 10 days earlier than the sun-loving blackcaps, grab the best territories and potentially, the best mates.
Meanwhile, blackcaps that winter in our gardens are developing longer bills and more rounded wingtips than southern rivals, possibly due to their more varied diet
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