ITS song is an iconic British sound that each year heralds the arrival of spring. Soon, though, the cuckoo's call could become as Scottish as bagpipes or Robert Burns' poetry.
While the species is in serious decline south of the Border, new research shows that in Scotland the birds are becoming increasingly common. The future looks so bleak for the birds in England that some experts believe Scotland could eventually become their last refuge within the UK.
An analysis of three years of bird sightings within 10km sq plots across the UK - for the British Trust for Ornithology's Bird Atlas 2007-11 - reveals cuckoos are thriving in Scotland, and in mass decline in England and Wales.
And the latest BTO Breeding Bird Survey shows cuckoos struggling to survive in large swathes of the UK. It revealed a 60 per cent decline in cuckoos between 1995 and 2008 in England, a 37 per cent decline in Wales, but a 6 per cent increase in Scotland.
Dawn Balmer, Bird Atlas co-ordinator with the BTO thinks cuckoos are growing in number in Scotland even faster than thought.
"Figures do suggest Scotland could become a refuge for cuckoos," she said.
Experts have theories about the change. These include varied food availability, loss of habitat in England and climate change causing shifts in breeding times.
"One thought is that adult cuckoos like fairly big caterpillars and maybe the food supply is better in Scotland," said Balmer. "This could have happened because of climate change."
It could also be linked to the cuckoo's ability to find a nest in which to lay eggs.
Cuckoos are parasites, laying their eggs in other birds' nests, but if the host bird, such as the meadow pipit, has started breeding earlier, their nests may not be available at the right time.
"They could be getting out of sync with each other," said Balmer.
Professor Jeremy Wilson, RSPB Scotland head of research, said: "Cuckoos seem to be faring much better in Scotland than in England. Indeed, numbers in the Highlands may well be increasing, while in lowland England they are declining fast."