Nesting seagulls added about £100,000 to the cost of demolishing empty hospital buildings.
The birds delayed the work to flatten former accommodation blocks at the Royal Gwent Hospital, Newport, paving the way for a planned car park.
Gulls are protected under the 1981 Wildlife and Countryside Act, making it illegal to intentionally disturb them while nesting, unless granted a licence, and offenders can face prison.
Breeding pairs court in March and build nests from April before laying eggs from April to May, with chicks usually appearing at the beginning of June.
In July, a nesting seagull caused a £460,000 overspend due to delays in demolishing Newport council’s former Newport Centre, a sports and events building, half a mile from the hospital.
The nests at the Royal Gwent, and a greater amount of asbestos in the buildings than originally anticipated, are forecast to cost the Aneurin Bevan University Health Board an additional £110,000.
The overspend has just been reported in the board’s budget for capital, or one-off spending costs.
The board, which manages the area’s NHS, said the buildings were eventually demolished last October.
“As it was discovered that seagulls were nesting on the building, we sought advice from Natural Resources Wales to coordinate the demolition outside of nesting season so as to avoid any harm to the birds,” it said.
