Sandwich Terns Make Slow Recovery After Devastating Virus Outbreak in Western Europe: Young Birds Seize Opportunity in New Nature Reserve

2023-06-11 10:25:15

Last year sandwich terns in Western Europe fell prey to the virus en masse. It is estimated that half of all breeding birds did not survive. Where 20,000 pairs of terns nested in the Netherlands and Flanders last year, only 10,000 are left now.

Young birds seize opportunity

Normally, terns do not start breeding until they are three or four years old. Until then, they usually stay in the wintering grounds in Africa or southern Europe. At the end of the breeding season, some birds sometimes come to ‘have a look’ in the breeding areas. Sometimes they even lay an egg, as if you never know.

“But last year those young birds suddenly had success,” observed ornithologist Mardik Leopold of Wageningen Marine Research. “Many old birds were already dead, so there was more room for the young. In the new nature reserve Prins Hendrik Zandijk, on the southeast side of Texel, the young birds still grew several hundred chicks.”

New variant

This year again many young birds settled on the Prins Hendrik Zanddijk. The first chicks have also been seen on the special webcam in this new nature reserve. “It seems that the virus has changed a bit, so sandwich terns are less affected this year. In the meantime, we are seeing black-headed gulls die en masse from this new variant in many places in our country,” says Leopold.

Guard tranquility

For forest ranger Thomas van der Es of Staatsbosbeheer, it is now important to keep a close eye on developments, using the webcam. “And we have to maintain peace in this vulnerable area. It helps to remove dead birds from the colony immediately, in order to stop the spread of the virus. But otherwise no one should enter the colony, with these birds that already so heavy.”

Slow recovery

Leopold emphasizes that it will take many years before the sandwich tern will recover from this blow. “These are birds that live a long time and produce few young each year. On average, only one chick hatches per two nests each year. So if there is another outbreak of bird flu among the sandwich terns, it will just take half a year century before you are back on the numbers before the virus outbreak.”