British researchers said it appears the number of birds that migrate to Europe from Africa every spring is in decline.
As many as 5 billion birds usually arrive in Europe each spring from their winter homes in Africa but those numbers are tumbling, Britain's Independent newspaper said Monday. A survey by the Royal Society for the Protection of Birds said 21 of the 36 British-African migrant species have declined significantly since 1967 and two -- the red-backed shrike and wryneck -- have become extinct in Britain.
Researchers said theories for the decline include habitat degradation in Africa and climate change. They said the problem may also be hazards on the migration journey or in the wintering grounds south of the Sahara Desert.
"We are seeing some very marked declines in migrants, which are giving us real cause for concern," RSPB conservation head David Gibbons told the newspaper.
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