Beach visitors are being urged to avoid a colony of nesting seabirds.
About 24 little terns have set up camp on the beach at Seaton Carew with more expected to follow, Hartlepool Borough Council said.
The legally protected birds winter in West Africa and nest in the UK between May and August.
The council's countryside manager Sarah Scarr said: "We would urge people to respect the site and keep their distance."
The birds first nested on the beach in 2019, she said.
The little tern weighs between 40g and 60g and is about the size of a starling.
The birds lay their well-camouflaged eggs in shallow scrapes in the sand which makes them "difficult to spot" and "extremely vulnerable to disturbance and damage", the council said.
The birds' nesting area at Seaton Carew, close to the resort's centre behind the bus station, is being marked and roped off, and volunteer wardens from the Durham Wildlife Trust are monitoring the site.
Ms Scarr said: "The majority of people who use the beach respect the nesting site but in previous years we have had cases of people walking through nesting site or letting their dogs off leads in the vicinity - in breach of a dog exclusion order which applies to this particular stretch of beach.
"Adult birds will leave their nests if disturbed, leaving their eggs and chicks vulnerable to the weather and predators."
A council spokesman said the penalty for deliberately disturbing or damaging the nesting site is an unlimited fine and up to six months in prison.