Tuesday, December 11, 2007

Seabirds Dying in the North Sea

This fall there have been several instances of mass deaths of seabirds in the North Sea. Their mortality has come to light when corpses washed ashore in Scandinavia and elsewhere. Most affected birds have been alcids.

The discovery of thousands of dead and dying auks, mainly razorbills, around the coasts of Denmark, southern Norway and Sweden, in September and October, didn't arouse widespread UK attention because there was comparatively little evidence of problems on this side of the North Sea.

But alarm bells rang after the latest British Trust for Ornithology BirdTrack Update referred to "a large wreck of auks seen along the north and east coasts, and as far afield as the Oslo fjord … All of these appear to have starved - and most were adults."

This disaster was of UK significance because, after the breeding season's end, Scotland's razorbills head for Scandinavian waters. This was underlined by numbered rings on several corpses: one started life on the Shiant isles off Lewis in the Outer Hebrides in 1982; another on the Isle of May off Fife on the mainland's east coast in 2000.
In addition to the razorbills, large numbers of guillemots and puffins have been found dead. Similar incidents have occurred elsewhere in the North Atlantic over the past several years. The cause of death in all cases appears to be starvation.
What caused particular concern, however, was that the birds were in an emaciated state - indicating failure to catch sufficient small fish to fuel their life on the open sea - and almost all were adults....

Kjell Isaksen, the Oslo municipality's biologist and wildlife manager, said "massive" number of dead and dying razorbills were washed ashore in his area. "Razorbills and guillemots were also seen on lakes far inland or found grounded on fields."

He had examined externally 60 per cent of 500 dead razorbills picked up locally and noted they were "only skin and bone", so emaciated he was surprised that birds originating in Scotland had been able to reach Norway. The conclusion in every case was "death by starvation."
The immediate cause of the food shortage has not yet been determined; the answer depends in part on where the birds died. Factors like overfishing and climate change would probably be immediate suspects; pollutants, disease, or perhaps invasive species could also play a role. In any case, the mass bird deaths are a sign that something is seriously wrong and needs to be corrected.