More than a dozen species of North American birds rarely seen in Britain and Ireland have been spotted along the countries’ western shores after being blown off their usual migration routes by remnants of Hurricane Lee and surviving the perilous journey across the Atlantic, experts said.
The arrival of warblers, vireos and other colorful birds last week has excited Britain’s twitching community — enthusiastic bird-watchers who will travel long distances to view new or unusual species. A sighting of a Canada warbler was the first recorded in Britain and similarly, a Blackburnian warbler was spotted in Ireland for the first time. Experts said twitchers should act fast if they want to see the North American arrivals, as the phenomenon will last just a few days longer.
Alexander Lees, an academic who specializes in biodiversity at Manchester Metropolitan University and the chairman of the British Ornithologists’ Union Records Committee, a group that maintains the official list of bird sightings in Britain, said on Tuesday that a series of storms had recently held up some bird migration in North America. When the birds decided to fly south for the winter, they were swept up in the remnants of Hurricane Lee, which made landfall in New England and Canada in mid-September before moving east toward Europe. That storm reached Britain and Ireland last week, bringing several inches of heavy rain to much of Wales and northwest England.
While some birds may have been able to reorient around the storm to stay on their migration route, tens of thousands of others were probably pushed out to sea, Dr. Lees said. A tiny number reached Britain and Ireland, he added.
“Normally, we get the storms later on in October and we get things like red-eyed vireos and yellow-billed cuckoos, and they’re almost sort of expected,” he said. “The fact that we got this early storm has meant that we got a different selection of birds, which has obviously been a boon for bird-watchers.”
Since last week, 16 species of North American land birds have been spotted in Britain and Ireland, including several species of warblers, one northern parula, 10 cliff swallows and three Baltimore orioles, Dr. Lees said. In total, more than 55 individual birds have been spotted.
Toby Phelps, an ornithologist for an environmental consultancy company, has had an exceptional week of bird-watching. Last Wednesday evening, while visiting family in Pembrokeshire, in southwest Wales, he spotted a magnolia warbler, a gray bird with a distinctive yellow chest. It was the third time the species was recorded in Britain and the first time seen on the mainland.
“When I saw that bird in the small valley that I walked through a lot of times in the past, it was just total disbelief and just the most amazing feeling that knowing this bird has crossed the Atlantic and ended up here,” Mr. Phelps said, adding that it looked healthy.
A few days later, Mr. Phelps tried his luck again, this time spotting the Canada warbler, a steely blue-gray bird with a yellow breast and black splotches around the neck. It was the first recorded sighting of the bird in Britain.
“For me personally, the finding of two really incredibly rare birds in Britain within the space of a few days is pretty unprecedented,” Mr. Phelps said. “I’ve had a lot of congratulations and stuff from other birders just for the finding of such rare birds within a short space of time.”
Dick Filby, the founder and owner of Rare Bird Alert, a bird news service in Britain, said the storm-blown birds were most likely the biggest such influx ever seen, resulting in a “massive increase” in the number of people looking for them.
“There are people traveling across the United Kingdom to see some of these birds because it is such an unprecedented arrival of North American land birds,” he said.
Mr. Filby, who was spending his 49th consecutive autumn on the Isles of Scilly, an archipelago off the southwest coast of England that is a renowned destination for bird-watchers, said there was a spirit of competition among the twitchers, but also a spirit of cooperation.
“The most magical part of this whole birding community, not just the birding community, but the fun of birding, is when you find for yourself one of these unusual birds that has come a long way and suddenly showed up in Britain,” Mr. Filby said. “That’s the ultimate dream.”
Twitchers will have a few more days to see the North American birds before many of them are expected to depart.
“Their first job is to feed up, to put on fat as fuel to continue their migration,” Dr. Lees said, noting that only birds that are strong fliers with the ability to rest on the sea stand a chance of making the journey back to North America. “For these small songbirds, the chances of ever getting back to where they’re supposed to be is incredibly small.”
Some of the birds will probably move south in search of suitable wintering areas and could travel as far south as central Africa, though they also face many risks.
“These birds are out of their habitat,” Dr. Lees said. “Can they find somewhere successfully for the winter? Can they find the right sorts of food? They don’t know the lay of the land, they are facing different predators, different pathogens. So, the chances of survival ultimately are very, very low for them.”