"Talk less, Fisher Blue! Keep your kindly wishes
Fly off and preen yourself with the bones of fishes!" Tom Bombadil .
The Kingfisher were a common fish-eating bird in Middle-earth. They were bright blue with a broad beak and yellow breast. Kingfishers were originally called the King's fisher, as they, like swans, were royal animals.
Kingfishers lived on the waterside, feeding on insects and fish. A notable Kingfisher existed, according to Hobbit folklore, in the Old Forest. It was known to harass Tom Bombadil, and as text shows, when flying away it lost a feather. Tom took the feather and replaced the old swan feather in his hat. He bore this noticable bright blue feather upon meeting Frodo Baggins and his companions in the Old Forest.
Gondor was also familiar with the Kingfisher; when Faramir saw what he thought was a black squirrel or kingfisher, he asked Anborn whether the were any black kingfishers in Mirkwood - a forest known for its black animals. Anborn saw the mysterious creature had four limbs, and quickly dismissed both ideas. It turned out to be Gollum hiding in the Forbidden Pool.