The first two of five cuckoos fitted with tiny tracking devices have defied the wet weather to return home.

Both Lyster and Chris have now arrived in Britain, bringing with them information which will potentially unlock the mystery of migration patterns of cuckoos which have evaded scientists until now.

The red-listed species has seen numbers halve in recent years, but experts have very little information on what happens to them once they leave the UK, with even their basic migration routes something of a mystery.

While one cuckcoo, Clement, died in Cameroon in March, and another, Martin, in northern Spain in April, the remaining bird, Kasper, was last heard from in Algeria on April 12.

The UK population is thought to have dropped by about 65pc – or almost two-thirds – over the past 25 years with fewer and fewer birds migrating back to this country each summer.

Experts at the British Trust for Ornithology, based in Thetford, said it was previously thought all cuckoos left for North Africa or Europe direct from their southern hemisphere wintering locations.

The new information however will allow them to assess what determines the number of cuckoos making it back to Britain each spring and why they arrive early or late.

For more, see tomorrow's paper.