Coming in from the cold

IN January 2007, a strange bird was seen on the sea off Farnham in Yorkshire.

It was clearly a member of the diver family, four species of which were on the British and Irish bird lists, but this individual looked somewhat odd. The definitive Collins Bird Guide did not feature the bird. Nor should it have done so: the visitor had come from the far side of the world.

Pacific divers move to inland lakes to breed but seldom travel very far from the sea. How, then, did this bird get to Europe? Had it flown across the landmasses of North America or Asia? Not very likely. Its presence remained an enigma. Then two more Pacific divers turned up, one off Cornwall, the other off Pembrokeshire. A sighting, last January, off the Clare coast near Ballyvaughan added the species to the Irish list. This, or another individual, has reappeared and is still there.

In America, divers are known as ‘loons’, an evocative term. You might think that the name comes from ‘luna’, Latin for moon as in ‘lunatic’, inspired by the mournful calls of divers on the lonely Arctic lakes where they breed. The great northern loon’s ‘song’ has even been mistaken for the howl of a wolf. The language experts, however, say that the name derives from an old Norse term, ‘lomn’, meaning ‘lame’. To become the world’s most proficient diving birds, loons had to position their legs so far back on their bodies that walking became impossible. Divers come ashore only to nest and, on land, they shuffle about awkwardly. Confined to the northern oceans, there are only five loon species. All of them are now on the Irish list.

But how did the new arrivals get here? Finding a sea route between the Atlantic and the Pacific was a problem for sailors as well as birds. The elusive Northwest Passage, from Baffin Bay east of Greenland to the Beaufort Sea north of Alaska, was once the Holy Grail of marine exploration. John Franklin’s two ships, with 128 crew members, vanished while searching for the elusive route in 1847. In those days, the passage remained almost permanently frozen but global warming has changed that; ships, and presumably birds, can negotiate the channel in summer.

Speaking on RTÉ’s Mooney Show, ornithologist Eric Dempsey suggested that this is the route which Pacific divers take to the North Atlantic.

There is, however, another possibility. Global warming has also opened the North East Passage, which stretches from the Bering Sea along the north coast of Russia to the Barents Sea and Norway’s North Cape. Pacific divers breed in Siberia east of the Lena River. The distance from Malin Head to the mouth of the Lena is 5,500km, about the same as that to Alaska via the Northwest passage. It seems more likely that the divers work their way along the Russian coast and down into European waters rather than crossing the Atlantic, having negotiated the Northwest Passage.

But divers are not the only strange visitors from the Pacific. The long-billed murrelet is a distant relative of our puffin. This little seabird nests in coniferous forests, sometimes far inland. An adventurous bird, it is prone to vagrancy, wandering the coasts of the Pacific Ocean.

In December 1997, one was found drowned in a fishing net on Lake Zurich in Switzerland. The carcass is now in the Natural History Museum in Basel. Another murrelet turned up in Devon in 2006 and a third was found on a reservoir in Romania shortly afterwards. It’s possible that these birds arrived via the Northwest Passage but, having reached the Atlantic, would they have embarked on a crossing of the ocean and then flown hundred of kilometres inland? Moving westwards along the north Russian coast and down through the Baltic Sea seems a more likely route; murrelets are diving seabirds more disposed to swimming than flying. They are likely, therefore, to remain close to a coastline.

Whatever the routes taken by the birds, these strange sightings of them are a clear indication that global warming is affecting marine ecosystems and that new vistas are opening up for some birds. Similar changes must be taking place within the sea itself, affecting the distributions of fish and invertebrates. The consequences of rapid climate change are complex and unpredictable.

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