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.
Three more of the warbler species face increased distances on their migratory journeys from sub-Saharan Africa as long as, or longer than, those faced by the Whitethroat, the study shows. These are birds of central and southern Europe which are not often found in Britain.
* The first is the Subalpine Warbler Sylvia cantillans a very pretty songbird with an orange breast set off by a white "moustache" which is found in southern Europe, especially around the Mediterranean coast. It faces an average increase in its journey of about 470 miles.
* The second is the Orphean Warbler Sylvia hortensis which looks rather like a larger version of the Blackcap familiar to English bird lovers, which has a very similar range to the Subalpine Warbler. It faces an increase in its journey of about 340 miles.
* The third is the Barred Warbler Sylvia nisoria a fairly inconspicuous bird of an ashy grey-brown colour, which migrates to breed in central and eastern Europe. It faces an average increase in its annual journeys of nearly 600 miles.
The researchers only studied 17 bird species in total and it is quite possible that many more migrants to Europe from Africa may face longer annual journeys.