A Middlesbrough pensioner said he feared thieves who stole his three owls now planned to sell them.
John Miller, 70, said he was devastated when he discovered the tawny owl and two barn owls had been taken.
Cleveland Police said a padlock was forced on an aviary at his home in College Road on Saturday night.
Mr Miller said he kept the owls as a hobby and was planning to breed the birds and then see if they could be prepared to be released into the wild.
He said he was "devastated".
He bought the owls on the internet and said they had rings on their legs.
But he said: "If they have got buyers for them they will cut the rings off."
He said he hoped the owls would be returned.
Police appealed for anyone with information to contact them.