The head of communications and development at Birdwatch Ireland has said the rare oriental turtle dove, discovered in a housing estate in Lisburn, Co Antrim, has probably been there since December.
Niall Hatch said householders locally said they had noticed seeing an unusual species, but no one realised it was a rare bird.
Mr Hatch said the news of the bird's presence broke last week after a local bird watcher shared images.
This in turn caused a huge gathering of twitchers to arrive in Lisburn.
It is the first time the bird has been seen on the island of Ireland, Mr Hatch added, so there is a lot of interest.
We need your consent to load this rte-player contentWe use rte-player to manage extra content that can set cookies on your device and collect data about your activity. Please review their details and accept them to load the content.Manage Preferences
"It's roughly the size of a feral pigeon, one of the city street pigeons. And it's quite dark. It's kind of hiding in the trees. It's been hard to see it.
"But actually, when you see it in good light, it's quite an attractive bird. Has sort of a scalloped tortoise shell pattern on the back, sort of a pinkish wash on the chest, a gray head, and it's got the sort of little black and white speckled half collar on each side of the neck."
Mr Hatch told Morning Ireland that no one knows how the bird arrived in Ireland.
It is a migratory bird, he explained, and populations that breed in places like Russia and Korea migrate to southern Asia for winter.
However, sometimes birds have something wrong with a gene that makes them migrate in the wrong direction.
"Most of those birds wouldn't survive. It's rare that one actually does. But the fact is, this bird seems to have travelled all that way from across two continents, really, across pretty much the entirety of Asia and Europe, to arrive in Lisburn.
"It's quite dramatic, really remarkable."
Mr Hatch said it is hard to know what will happen next with the dove.
"We are getting to the time of year when migration instincts kick in with these birds", he added, "and it may be that this bird will be compelled to move elsewhere".
