A team of top British ornithologists is to fly to sub-Saharan Africa to investigate the mysterious decline in summer visitor numbers to the UK of popular birds like the cuckoo, the turtle dove and the nightingale.

A joint team from the Royal Society for the Protection of Birds and the British Trust for Ornithology hopes to discover why the greatest declines of birds in the UK are among those species which spend the summer in Europe but winter in Africa.

Recent figures suggest that more than 40 per cent of all migratory species passing between Europe and Africa have declined in the last three decades. Alarmingly, one in 10 of these are considered to be of global conservation concern.

The project will involve researchers monitoring birds along a corridor stretching from Ghana’s Atlantic coast to northern Burkina Faso, spanning a range of habitats from coastal rainforest to the edge of the Sahara desert.

The RSPB's Dr Danaë Sheehan, who will be monitoring birds in West Africa, said: “The drastic declines of some of our best-loved summer-visiting birds, such as the cuckoo, turtle dove and nightingale is one of the greatest concerns currently raging in conservation.”

“Although we have a reasonable understanding of these birds in the UK, we have little or no idea what's happening to them in their wintering grounds. It is clear that without help these declines are likely to continue, reducing the populations of these summer visitors to dangerously low levels.”