Common Cuckoos from the UK are being tracked using satellite tags in a bid to find out more about their migration patterns and whether or not these are affecting their population numbers.
The British Trust for Ornithology (BTO) has put the tags on eight of the birds over the past few weeks, including three from North Yorkshire, two in Lancashire and one in Sherwood Forest, Nottinghamshire.
Information has already come in from the latter bird showing that he had reached northern France on his way to the Congo rainforest of Africa.
During their studies over the past four years, scientists have discovered that Cuckoos follow two distinct patterns of migration - the first takes the birds through the western Mediterranean via Spain, Morocco and West Africa, while the second crosses the central Mediterranean through Italy and the central Sahara.
Interestingly, Cuckoos from England have all been found to take the western route, while those tagged in Scotland and Wales go via the central route.
Over the past 25 years, Common Cuckoos in England have demonstrated significant population losses in England with nearly three-quarters of the birds being lost, while numbers in Scotland have recovered by three per cent in around a decade.
The scientists at the BTO now want to know if these factors are connected - and which exact route the birds from the north of England are taking.
Lead BTO scientist on the project Dr Chris Hewson said: "The cuckoo project has entered a very exciting phase. We are now completing our knowledge of what cuckoos from different parts of the UK do, and how this might be affecting populations in different areas."
You can follow the tagged Cuckoos' progress on the BTO website.
In the meantime, look out for them while you're out and about before these summer visitors head back off to Africa. They are dove-sized with blue-grey bodies, heads and chests, while their under-sections are striped with black bars.
Unfortunately, Cuckoos are now on the Red List for conservation due to their recent population declines.