Tuesday, April 14, 2009

Tiny warbler (and other birds) at risk from longer African migration

The Independent (UK): They are some of the world's most remarkable and improbable journeys – vast odysseys across desert, mountain and sea by creatures often no bigger than a Mars bar. But the annual flights of Europe's migratory birds to and from sub-Saharan Africa are set to get even longer.

Climate change, shifting the breeding range of many European bird species northwards, is likely to lengthen the migrants' marathon journeys substantially, in some cases by hundreds of miles, a new scientific study predicts. The added distance is likely to make what are already hazardous and chancey long-distance flights even more risky, with possible fatal consequences for many birds.

One example is one of Britain's most charming summer visitors, the whitethroat, a small bouncy warbler pouring into Britain by the thousands right now after journeying from its winter quarters in the Sahel, the arid zone south of the Sahara. The whitethroat may face another 300 miles or more on the average length of its Africa to Europe trip by the end of this century. This added distance would be a considerable threat, said Stephen Willis of Durham University, leader of the research team which produced the study.

The researchers have carried out the first examination of how global warming may, by the end of the century, affect the "climate space" of European breeding birds on their wintering grounds in Africa – the climate space being the climatic range in which they can comfortably exist. This is a follow-up to a study last year, extensively reported in The Independent, which showed that many birds' climate space in Europe would shift towards the north as temperatures rose.

But the new study shows that for the bird group studied – the Sylvia family of warblers, of which the whitethroat (Sylvia communis) is one – the African climate space does not move in some cases, while the European one does, meaning that the migratory journey gets longer….

This image of Sylvia communis comes from the book Naumann, Naturgeschichte der Vögel Mitteleuropas (Natural history of the birds of central Europe) of 1905 or his earlier works. The copyrights for those books have expired and this image is in the public domain

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