THE first swallows arrived in the Yorkshire Dales ten days ago but bird scientists are asking the general public to keep a weather eye open this week for a mass invasion of their cousins, the swifts.
Swifts make a welcome return to the Yorkshire Dales
Photo: Mike Toms/BTO
Swifts, which spend the winter south of the Sahara, tend to arrive in Britain en masse in the third week in April after one of the most exhausting ordeals known to nature: they will have spent the entire eight months on the wing since they last took off from Britain last autumn.
The British Trust for Ornithology explains that, in Africa, they tend to fly at high altitudes and actually sleep on the wing, shutting down half their brains at a time to achieve this amazing feat.
They are also known in some parts of the world as "devil birds" because of their high-pitched screaming call.
The BTO, which pioneered the use of mass bird censuses by asking thousands of Britons to report their first sightings of migrating on the Internet as part of its massive Birdtrack programme, is asking people to log their first swift sighting on www.birdtrack.net
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