LONDON—In a feat attributed to the heat wave that swept across Europe, rare Andean flamingos at a wetlands reserve in Britain have laid eggs for the first time in 15 years.

The exotic birds are “fickle breeders” and can go years without nesting successfully, the Wildfowl and Wetlands Trust in Slimbridge, England, said in a statement this past week.

But amid scorching temperatures on the Continent — which have spawned wildfires in England and Wales, melted glaciers in Austria and Sweden, and broken records in Portugal — a surprising thing happened at the reserve.

Six of the flock laid nine eggs, which Mark Roberts, the aviculture manager at the reserve, called “a wonderful and welcome surprise.”

“We’ve been encouraging the flock by helping them to build nests,” he said in the statement, “but there’s no doubt that the recent heat has had the desired effect.”

Unfortunately, the organization said, all the eggs were infertile, so no new Andean flamingos will emerge from this batch.

So in a bit of human meddling, caretakers decided to get the Andean birds in parenting mode: They took a few eggs from Chilean flamingos, “near relatives,” and planted them among the Andean birds, who became foster parents to new chicks, the reserve said.

A spokesperson for the organization, which is based in Gloucestershire, said by phone on Saturday that the Andean flamingos were some of the oldest at Slimbridge, which describes itself as the only such reserve where all six flamingo species roam.

A few flamingos arrived in the 1960s, according to the reserve, and some of them have been there longer than staff members.

Both the Andean and Chilean flamingos are considered at risk of extinction by the International Union for Conservation of Nature. The Chilean birds are described as “near threatened” because of egg-harvesting, hunting, disturbance and the loss of habitat, while the Andean ones are called “vulnerable” because of past exploitation that shrank their population.

The heat wave broke in other parts of Europe, meanwhile, unleashing torrents of rain that caused flash flooding in France. Officials used helicopters to rescue about 1,600 people, mostly campers, in three regions in southern France, Interior Minister Gérard Collomb said in a statement, according to The Associated Press.

In Switzerland, footage emerged this past week of a mudslide hitting the village of Grugnay in the municipality of Chamoson, as witnesses scrambled to safety.

No injuries were reported after the mudslide, which local news outlets said had begun after storms caused a river to burst its banks.