“Free range will likely be endangered”

Mass deaths of seabirds are occurring on the coasts of Germany, Great Britain and Iceland, in Greenland and on the North American Atlantic coast. Bird flu has been rampant for an unusually long time this year and has become extremely widespread. Timm Harder, head of the national reference laboratory for avian influenza at the Friedrich Loeffler Institute on the island of Riems, explains why people cannot be indifferent to this epidemic – and why large vaccination campaigns are necessary.

In Germany, we have witnessed massive deaths among seabirds in recent weeks. Bird conservationists assume, for example, that 70 to 80 percent of the nests in Germany’s only colony of gannets on Heligoland were abandoned prematurely. How bad is the situation?

The large and well-known seabird colonies such as those on Helgoland or on Bass Rock, the counterpart in Scotland, are probably only a small selection. Much attention is paid to such colonies. The virus that causes these deaths, the highly pathogenic avian influenza H5N1, has now been detected in seabirds along the entire German North Sea and Baltic Sea coast, even in the entire North Atlantic. Last year it made the leap from Europe to North America via Iceland and Greenland. It is the worst epidemic we have ever experienced, ultimately affecting all seabirds that breed in colonies. In the summer of 2007 in Germany we experienced a small epidemic at the reservoir near Kelbra in the southern Harz Mountains, in which almost all the rare black-necked grebes that molted there died. But what we are experiencing now has a completely new dimension. This outbreak of avian influenza in wild birds is unprecedented in its extent in terms of time and space.

Colonies offer protection from predators, especially for ground-nesting birds, but are – as you can see – a virus trap. Why?

The nests are usually just a wingspan apart. There is feces and other excretions everywhere, and transmission can also occur when birds fight or bill directly with each other.

Why is the virus raging so fiercely this year?

That surprised even us scientists. We have had some strong avian flu seasons, for example 2016/17 and 2020/21, but the virus usually disappeared by the start of spring, before the large colonies of birds started breeding. This year, for the first time, there was no seasonality – the virus was able to multiply throughout spring and summer.

They continuously sequence samples from dead birds at the FLI and in other reference laboratories for avian influenza. Thanks to these sequences, have they been able to see the trick of the viruses that have made them so resilient to the warmer temperatures and drought this year?

No, we don’t see any glaring differences from the viruses that circulated in 2020 or 2021. We don’t know what exactly is different.

Are only birds that breed in colonies affected?

Mainly yes. But we have also found the virus in raptors that eat other birds as predators.

What about songbirds?