European songbirds are canceling their annual winter breaks in Africa, preferring instead to fly to Great Britain, bird experts say. The surprising detour in European warbler migrations was revealed by data from an ongoing survey that involves bird-watchers across Britain. The survey shows that rising numbers of warblers, which spend their summers in northern Europe, are no longer flying south to Africa and the Mediterranean each fall. 

"I am amazed by the numbers of warblers that were reported," said Greg Conway, a researcher with the British Trust for Ornithology (BTO), who runs the survey. It's as if the birds are now saying, "Let's not bother to go all the way to Africa this winter," he said. Eleven species of migratory warblers wintered in Britain last year. Reports from more than a thousand British birdwatchers included sightings of around 1,500 blackcaps (Sylvia atricapilla) and almost 1,000 chiffchaffs (Phylloscopus collybita).

"The blackcaps are almost exclusively birds which breed in Germany and central Europe and are coming [to Britain] for the wintertime instead of going to Africa," said BTO songbird expert Graham Appleton. Appleton says the wintering chiffchaff population is made up mainly of British birds that are staying put, plus some visitors from mainland Europe. Other reported species usually not seen during the British winter included willow warblers, garden warblers, reed warblers, and whitethroats.

Winter Warblers The warblers' migration to Britain instead of Africa could be a response to global warming. Increasingly mild winters mean the birds can now cope with Europe's coldest months, giving them a head start the following breeding season.

"The decision not to travel south across the Sahara Desert may have some clear benefits: boosting overwinter survival and leading to an increase in breeding populations," Appleton said. Bird experts have found that some warblers have a genetic disposition to fly west instead of south in the fall. Previously these birds would have perished in the cold European winter. But many now survive and pass this migratory trait to their offspring.