By Helen Briggs BBC News
19 July 2016
The sound of the first cuckoo in spring is a familiar one in the British countryside.
But the summer visitor is in decline and, according to a new study, its migratory habits may be to blame.
Scientists have tagged birds leaving the UK and believe they take two different routes on their journey to spend the winter in Africa.
Surprisingly, survival is lower on the shorter route via Spain, they report in the journal, Nature Communications.
And this suggests that migration - as well as other factors such as loss of farmland and insect food - may be to blame for the cuckoo's decline.
More than half of cuckoos in the UK have been lost over the past 20 years, according to the British Trust for Ornithology (BTO) in Norfolk, which led the research.
"That pattern of starting in the same place but taking two very different routes to get there has not been seen before in any birds, to the best of our knowledge," said lead researcher Dr Chris Hewson.
"We need to understand the full annual cycle of a migratory bird in order to understand its population decline."