The female was tagged last summer in Renfrewshire but was this month spotted in the Caribbean.
It is estimated they left Scotland on migration in late August or early September.
Mr Mackrill said some Finnish Ospreys were known to migrate to South Africa for winter, which is a greater distance.Its route is thought to have been from south-west Ireland to Barbados, which is about 3,800 miles.Mr Mackrill said: "It is highly unlikely that even an osprey could have completed this in a single flight, even with strong tailwinds, and so it is probable that she took the opportunity to rest on boats, which may themselves have been travelling to the Caribbean from the UK.
Mr Mackrill said the bird appeared "very settled" and may well remain on the island for the foreseeable future. Duncan Orr-Ewing, RSPB Scotland's head of species and land management, said: "Ospreys never cease to amaze us with their incredible exploits but this latest sighting of a ringed Scottish osprey in Barbados is certainly one of the best yet.
"The RSPB is pleased to have played a pioneering role in Scotland, encouraging the osprey's return as a breeding bird from the 1950s at Loch Garten in the Highlands, and we can now see this species gradually re-occupying all of its former range across the UK."
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