Thieves snatched 60 racing pigeons after breaking into a shed at an allotment site in Doncaster.
Police are appealing for witnesses to the theft which happened on land off The Oval, Dunscroft, between 4.45pm on Friday 18 October and 9.30am the next morning.
The suspects damaged a fence and forced a lock on the shed in order to get to the birds, owned by a 54-year-old man from Stainforth.
All the stolen pigeons are of mixed colours but can be identified by a ring featuring the serial number DY2008.
Officers believe the suspects would have taken a long time to remove the birds in boxes, either taking them to a vehicle or walking off with them.
PC David Connolly, from Stainforth Safer Neighbourhood Team, said: “These are racing pigeons which, if sold, are worth a considerable amount of money.
“The owner is understandably distraught by the theft and I would urge anyone who has been offered the birds for sale, or who has any information about the theft, to call police immediately.”
Witnesses or anyone with information should call South Yorkshire Police on 101, quoting incident number 409 of 19 October.