A nesting moorhen has cost Crawley Borough Council £2,000.
The bird brought improvement works at Dobbins Pond, Ifield, to a halt when she chose to lay her eggs there.
Now the council must wait more than two months for the chicks to hatch and fledge before the work can continue.
A council spokesman confirmed the nest would not be disturbed while still in use, in accordance with the Wildlife and Countryside Act 1981.
He added: “We have been advised that the incubation period will be up to 21 days with up to a further 50 days until the chicks have fledged.
“We are monitoring the nest from afar and it will be removed when it becomes dormant.
“This delay will cost approximately £2,000 to demobilise the contractor and for the additional cost of hired fencing.
“Crawley Borough Council is committed to protecting the local environment and we thank residents for their patience during the delay.”
The improvement work is part of an investment programme in community facilities in Ifield West.
This includes removing duck weed, rebuilding the spillway and installing a footbridge, footpath and picnic area.