An “unprecedented” influx of alpine swifts has been reported by birdwatchers across Britain and Ireland. Dozens of these migrating birds, which usually fly thousands of miles from sub-Saharan west Africa to southern Europe to breed at this time of year, have been spotted around the Irish coast as well as in parts of Wales, England and even as far north as Scotland. Unlike more familiar common swifts, which tend to arrive to Britain and Ireland in May, Alpine swifts have a giveaway white belly and throat. “Seeing one from my kitchen window was the best,” said Jane Crossen, a birdwatcher in Norfolk. She sighted the bird, or possibly two different individuals, multiple times in the town of Sheringham on Monday. Extraordinary numbers were reported in Ireland in recent days, where up to 60 alpine swifts have been recorded so far, according to the Irish Rare and Scarce Bird news group. The previous record for most alpine swifts observed together in Ireland was five. This has been broken twice in the last week or so, first by a flock of seven birds in Dungarvan, County Waterford, and then by a group of nine seen flying together near Dublin, said Owen Foley, an analytical chemist and amateur birdwatcher who helps to run the group. On Monday, Christopher O’Sullivan, TD (member of parliament), tweeted a video of one of the swifts flying in County Cork. The bird news website Bird Guides suggested that a funnel of south-westerly winds had helped to push the swifts towards Britain and Ireland. “It is unprecedented. Usually we’re lucky to get two or three birds a year,” said Rob Robinson, of the British Trust for Ornithology, who has studied seasonal migration in alpine swifts. He noted that the species had spread further north during the postwar period, with the birds increasingly making their nests in the roof crevices of buildings in Europe, rather than their natural breeding habitat of openings in cliffs or caves. However, he added that no one was sure what was behind this switch in preference. It was difficult to know whether the climate crisis had influenced the bountiful arrival of alpine swifts to this part of the world, said Robinson, but he added that large influx events such as this could become more common as global heating upended traditional weather patterns. Rising temperatures could also deter various bird species from the southernmost parts of their breeding ranges, he added. Such a phenomenon has been documented with willow warblers in England, for instance. Foley doubted that the climate crisis had influenced the present boom in alpine swift numbers and he expected them to move back to the continent to breed. But he predicted that the birds would continue arriving in Ireland for some days to come. “They’re still out there, they’re going to be popping up for the rest of the week at least, I think,” he said.