Four cuckoos have been caught at sites in Lochalsh and Skye and fitted with satellite tags in an effort to track their migrations from Scotland.
The birds were trapped on the National Trust for Scotland's Kintail and Balmacara estates and Forestry Commission land at Kinloch on Skye.
Staff from the British Trust for Ornithology fitted the transmitters.
Two out of five cuckoos tagged in the Trossachs in 2012 survived their migration to Africa's Congo Basin.
The Lochalsh and Skye birds are now the most northerly in Britain to be tracked to date.
John Calladine, of the BTO, said cuckoos were once common and widespread across Britain before declining in numbers in some parts of the country.
He said: "Being able to follow their individual movements to the Congo Basin and back is inherently fascinating.
"An important part of this work will be in identifying areas and habitats used by the birds throughout the year, even across years.
"It will help towards identifying reasons as to why the north and west has become a refuge for these and other species and suggest ways to ensure that remains the case."