A pair of nesting kestrels have halted repairs on the Forth Road Bridge.
A nest containing six eggs was spotted just inches underneath the bridge's carriageway.
The birds seemed unperturbed by the noise and vibration of 80,000 vehicles a day crossing the bridge just above their heads.
The discovery inside the end of a girder was made by workers repairing steelwork.
Work in the area has been suspended.
Bridge officials said the kestrels are thought to have taken over a nest built by another bird, such as a pigeon, as they do not make their own.
Maintenance supervisor David Gill said: “When we saw the eggs, we immediately cleared the area and instructed staff to avoid carrying out any works that might disturb the nest.
“I’ve heard of kestrels nesting on the bridge before, but it’s pretty unusual.
"You’d think they might prefer a quieter location.
“We’re happy to have them here though, and have affectionately named them "Mr and Mrs Younger".
“We’ll come back and finish our repairs once the chicks have hatched and flown the nest.
"In the meantime, we’ve carried out a temporary repair on a local defect - quietly.
"There won’t be any impact on users of the bridge.”
Officials said the birds of prey were protected under the Wildlife and Countryside Act 1981, which makes it an offence to kill, injure or take a kestrel, or to take, damage or destroy an active nest or its contents.
They said birds nested on the bridge from time to time, but they usually don't cause major problems.
However, experts had to be drafted in to scare away thousands of starlings which nested on the bridge.
Birds nests have also halted trains after caused electrical faults in overhead power line gantries.
Incidents have included at Hyndland in Glasgow last month and between Port Glasgow and Gourock in March.