Enthusiasts have been flocking to catch a glimpse of the two avocets since they were spotted at Belfast docks RSPB reserve at the weekend.
The bird last bred in Ireland in 1938 and there are hopes this mating pair could produce chicks here.
The bird, with its distinctive black and white markings and curved beak, is resident in a number of places in England but rarely seen this far north.
It is also the symbol of the RSPB.
It had disappeared in England until a major conservation effort by the charity led to its return in the 1940s.
The RSPB's warden manager Chris Sturgeon said it had been "manic" since news of the avocets' arrival spread.
"Word gets about pretty quickly and everybody arrives," he said.
"Some people will never have seen an avocet before, it's certainly the first one I've seen in Northern Ireland."
If the pair does produce chicks, the main threat to their offspring will be from predatory birds.
Avocets live on insects, crustaceans and worms in the mud.
The appearance of a rare pair of waders has Belfast birdwatchers in a flap.