Night herons are among the most mysterious of birds, and for the first time in recorded history they have been spotted breeding in the UK.

Long-distance photographs captured an adult pair of black-crowned herons and one of their two offspring at the Westhay Moor national nature reserve, run by Somerset Wildlife Trust. The young birds have recently fledged, having been born either on Westhay Moor or the nearby Avalon Marshes.

The night heron (Nycticorax nycticorax) is unusual among the heron family in hunting for fish and frogs at night. They roost during the day and can only usually be spotted at dawn and dusk.

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“This is incredible news,” said Stephen Moss, president of Somerset Wildlife Trust. “To put it in perspective, when I was a young birder in the 1970s, just two species of heron bred in Britain – the grey heron and the bittern. But these night herons are now the seventh member of their family to nest in the Avalon Marshes.” These include both cranes and glossy ibis.

“I am sure climate change has drawn them north, but equally wetland restoration has been a massive success,” he said. “We have created an incredible habitat.”

Ornithologists will now wait to see if the night heron becomes established in the UK. “They may hang around, if there is enough food. If not they will probably nip back to France or Spain,” Moss said.

Roger Dickey, chairman of Somerset Ornithological Society, said: “This is obviously terribly exciting news. Night herons are one of southern England’s rarer summer visitors and only a dozen or so have been reported in Somerset since 1800. Prime breeding areas do not happen by accident and all organisations and individuals that help to manage this type of habitat are [to be] congratulated.”

Purple herons were first reported as successfully breeding in the UK in 2010, on the Dungeness peninsula, Kent, and have since been seen in Essex.

Although global warming appears to be beneficial for herons in the UK, a recent report found it is harming sea birds, such as puffins, fulmars, terns and razorbills, as the fish they rely on are driven north or deeper as waters warm.