The roseate tern is on the brink of extinction here, with just one pair breeding on Larne Lough last year.
The birds hatched one chick, although there were reports of an influx of the animals in late summer, thought to have come from Dublin.
The British Trust for Ornithology said: "They're on the brink in Northern Ireland. They've been teetering for years. It'll be a crying shame if they go.
"The population is concentrated on one island off Dublin and I'd love some of those to move out and breed elsewhere. We're trying to encourage them to come back by providing good nesting habitat."
The RSPB said £2.5m had been awarded by the EU's LIFE Programme to carry out an ambitious five-year project to restore roseate terns. "As part of this, gravel will be moved to the site to build up the island and nest boxes will be put in place," it added.