The bird was last seen in the UK in 1985
Some twitchers have travelled more than 400 miles to North Uist in the Outer Hebridies to try to get a glimpse.
The bird - called the black billed cuckoo - is native to North America and has only been spotted 15 times in the UK.
Some spotters are so keen to see the bird they have charted a private plane.
The rare bird arrived on North Uist in the Outer Hebridies last weekend and since then groups of birdwatchers have been making the trip out to see it some travelling from the south east of England to get a glimpse.
This is believed to be the only time a Black Billed Cuckoo has arrived on these shores in the Spring with other sightings taking part in the Autumn when the birds get caught up in storms and buffeted over to the UK.
The cuckoo would have spent the winter in South America and while journeying back to North America it has ended up managed to cross the Atlantic.
The Black billed cuckoo, as the name suggests, has a black beak and, although a similar shape to the common cuckoo, they have very different plummage.
James Halton, 41, and lifelong birdwatcher hotfooted it from Cambridge up to North Uist in a plane.
He said: "It has created quite a lot of excitement. We travelled up in a small chartered plane, it's something I do maybe two-three times a year when birds of this magnitude appear.
"You just have to get there as fast as you can and if that means going by plane the next day or the same day then so be it.
It probably got to north america, saw what the weather was like and said 'sod this, i going to scotland!'