The unsuspecting swimmers who had stripped off for a naked dip were baffled by the disappearance of their pants and socks as they cooled off au naturel at a popular bathing spot near Glen Esk in Angus.
But the mystery was solved when a gamekeeper stumbled cross a natty nest of a local pair of red kites - lined with pilfered pants and stolen socks.
Dave Clement, head keeper at the Gannochy Estate, said: "Our trainee gamekeeper discovered the nest and we rang the RSPB to have them ringed and tagged.
"What was really interesting was to see socks and underwear from a popular swimming spot actually in the nest and the surrounding trees.
"It was like the kites were cleaning up the glen."
Two red kite chicks were later discovered in the new nest - proving that the clever insulating tactic has paid off.
This isn't the first time kleptomaniac animals have made the headlines.