Scientists and birders watching the extraordinary and disturbing midwinter migration of hundreds of snowy owls from the Arctic admit that they don’t know why so many of the birds are departing their natural wintering grounds.
One observer used the word “unbelievable.” Another said that it was the “most significant wildlife event in decades.” Like the word ‘surprise’, the implications are not necessarily good. A heart attack is almost always a surprise.
Another watcher suggested that the mass migrations are the result of a bumper crop of lemmings last year, which led to snowy owls raising large broods – five to seven, as opposed to the usual two. Lemmings are the snowy owl’s primary diet.
Migration is nothing new to these magnificent birds, which stand two feet tall with a five-foot wingspan. In fact, every year a few leave their northern breeding grounds for such remote locations as Missouri, Idaho and Massachusetts.
In a normal season, these abrupt and solitary departures from routine and territory are very much like the anomalous environmental prompts that induce moose to wander far from their habitat (roughly north of 47 degrees north with a thumb extending down into the Rocky Mountains) to explore in solitary splendor the cornfields of Iowa and – even more occasionally – the second growth forests of Oregon.
When moose do it, it is sometimes ascribed to a brain parasite, or brainworm (parelaphostrongylus tenuis) that causes neurologic damage and disorientation. The worm is, in effect, the moose equivalent of Alzheimer’s. Fortunately, moose can’t drive.
But neither the brainworm nor any other parasite is known to cause snowy owls to, literally, lose their place in the world. And certainly never before in recorded history in such numbers as are being documented this winter.
The migrations are even being described as “outbreaks”, as though they were a disease. And they may well be just that, though an illness whose cause is more obscure than a worm, and no doubt hidden in the reams of data surrounding global climate change and its causes.
This migration, amongst a species so remote it is difficult to study – and now deeply in decline thanks to a rapidly changing climate – may be like that fabled last flight of the condor , whose final member was captured on Easter Sunday, 1987, in the bluer-than-blue skies above the San Mateo range in California.
For those lucky few who have seen snowy owls as far south as Oklahoma this winter, cherish the memory. You likely saw history in the making, and the end of a species.
da qui grazie