The call of the cuckoo used to be a sure sign that summer was on its way, but with a 35% fall in the UK’s breeding population since 1995, we hear fewer of these calls with each passing year. The reasons for their decline are, however, not fully understood.
While it’s long been known that cuckoos spend their winters in Africa before flying to the UK to breed, the specifics of their migration routes have proved difficult to study.
This information could, however, give clues as to why the UK breeding population is in decline, and thus how the birds might be best protected. Scientists at the British Trust for Ornithology (BTO) have therefore been busy attaching satellite tags to cuckoos. These tags transmit real-time location data, allowing scientists to get a detailed view of cuckoo migration routes.
Data from the tags has already revealed fascinating insights into cuckoo migration. For example, individual cuckoos have markedly different migration routes. Individuals that fly from areas of the UK where the breeding population is in decline tend to take more westerly routes over Europe, via Spain. Meanwhile, individuals that fly from areas with less obvious declines tend to take more easterly routes, via Italy or Greece.
Next, scientists hope to dig into how the migration route an individual takes might influence their survival. "Understanding the dangers that many of these birds face as they migrate vast distances can help us to consider how we might help to protect them,” says lead scientist on the project, Dr Chris Hewson.
Alongside information on migration routes, the tags have also revealed that male cuckoos spend a much shorter time in the UK than previously thought, with some individuals staying in the UK for just a month before heading back to Africa.
“This ongoing project opens a significant window on the wonders of migration,” Dr Hewson says. But it’s not just the scientists who have been avidly tracking the tagged birds. The tags provide live location data which is published on an online map. Members of the public can therefore watch the cuckoos’ incredible journeys, too.
While the decline of the cuckoo is worrying, studies like these build a foundation from which effective conservation plans can be built. Hopefully, the call of the cuckoo will signal the start of the British summer for generations to come.
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