On the mainland coast, the epidemic has mainly affected various tern species in recent weeks, especially sandwich terns. Like all seabirds, they breed in densely packed colonies. Are other species affected on Heligoland?
So far only gannets have been found here. The other cliff nesters, ie kittiwake, guillemot, razorbill and fulmar, breed normally as far as we can tell. The great gulls – herring gulls and lesser black-backed gulls – have not been affected here either, while there are now more dead finds of these species in the Wadden Sea. We took samples from several bird species: gray geese, sandwich terns and eider ducks were negative.
Northern gannets in Germany: a success story so far
So far, the development of the only German gannet colony on Helgoland has only gone in one direction: upwards. The species first bred in 1991 on the small offshore island. By the early 2000s, the number of breeding pairs had risen relatively slowly to almost 100, after which there was a sharp increase in numbers, which – albeit not so steeply – has continued to this day. At the beginning of the current breeding season in 2022, ornithologists counted 1485 breeding pairs.
Gannets are extremely well adapted to hunting fish. With angled wings, they shoot torpedo-like into the sea from a height of dozens of meters in order to capture fish. The birds stay on the Atlantic all year round. Juveniles migrate to the West African coast in autumn, where they often stay for a year or two before returning to their native areas. They only become sexually mature when they are four to five years old.
Helgoland is the only place in Germany where gannets breed. What does the bird flu outbreak mean for the future of the species here in this country?
The numbers are definitely alarming. We can’t say how bad they are yet. The lifestyle of the birds also makes them particularly vulnerable: gannets only become sexually mature late and they lay a maximum of one egg per year. They are therefore dependent on reaching a certain age in order to contribute to the survival of the species. A bird that dies at seven may have only successfully bred once or twice. So it’s worrying when so many adult birds die. There are other dangers for the birds as well.
Which would that be?
Even the problem of plastic waste has a significant impact on the colonies. The birds collect plastic strands floating in the sea and weave them in their nests, mistaking them for algae, which they normally use to build nests. Around five percent of the birds in our colony strangle themselves on these plastic threads. And if about five percent of the adult birds die, that has a measurable impact on the population here because of the reproductive strategy just explained. Now there’s bird flu. That will be difficult then.