The first bee-eater chick has fledged at a quarry in Trimingham in north Norfolk.
Eight bee-eaters took up residence at the quarry in early June and soon began excavating nest burrows.
The first chick fledged just before 9am on Tuesday morning and a second chick is expected to fledge any day.
Jenny Shelton, RSPB investigations liaison officer, said: "We've got at least four chicks in two nests.
"They should all be out this week, and the very soon after that, the whole group should fly back to Africa."
Ms Shelton said the last time a bee-eater chick had made it as far as fledging in the UK was in 2015.
She said: "It's a momentous moment and a real testament to the volunteers who have been monitoring the site 24/7."
Ms Shelton said predators such as kestrels, sparrow hawks and stoats had been spotted near the site, but thankfully the bee-eaters had been spared.
She said thousands of people including many visitors to Norfolk who were holidaying along the coast had made their way to a special viewing platform set up on land next to the quarry site to see the brightly-coloured birds.
Having previously been rare visitors, breeding attempts by these brightly-coloured birds are increasing in the UK, with six recorded in the past 20 years.
Bee-eaters normally nest in southern Europe and northern Africa, and the expansion of their northern range is a warning that rising temperatures, due to climate change, will become the norm without urgent action.
Ms Shelton said: "It shows that as the temperatures in the world are rising the bee-eaters are going further north.
"It's going to become more normal to see them in the UK."
About the size of a starling, bee-eaters are unmistakable with their claret-red backs, yellow throats and turquoise bellies.
Bee-eaters raise their chicks communally, and single birds from a previous brood are likely to help out the two breeding pairs with duties like incubating and feeding.
As well as various species of bee, they feed on dragonflies and other flying insects, which they catch in mid-air.
A live stream of the bee-eater nest can be found online at Youtube. Search for Bee Eater Live Nest Cam.
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