ANOTHER LIFE: Mayo's snowy owls - how much of a surprise? When it comes to near and distant cataclysms, lamentations, rumoured wrath of the gods, our anguished forebears can't have had much more to put up with than we do. On omens and portents, however (such as berries and hard winters) we are more relaxed: science offers new ones every day, writes Michael Viney.
Thus, the only clamour raised by the appearance of an Arctic snowy owl on Mayo's Mullet peninsula last month has been among city twitchers, heading west with their telescopes and cameras and text-messaging each other about the choice of pubs in Belmullet. An early result was a photograph on their favourite website (http://www.birdsireland.com) showing a gleaming specimen of Nyctea scandiaca dozing in winter sunshine among the Mullet's granite boulders.
Later twitchers, however, had to brave a north-westerly storm, and few of them can have pushed on to the bleak height of Fallmore, at the Mullet's southern tip, where even the great megaliths of Michael Bulfin's spiral henge would have offered purely nominal shelter. The owl, if it had any sense, was probably holed up at this time in a convenient ruin across the foam on Inishkea, a favourite Irish retreat of these winter wanderers.
Here, indeed, another male snowy owl spent several summer weeks on the island and was duly mist-netted and ringed by David Cabot, more usually the registrar of Inishkea's winter geese.
It was at Fallmore, however, that Dúchas conservation ranger Tony Murray happened to see the new arrival (a younger bird) casting up two big, prickly pellets of undigested bones, fur and feathers, twice the size of Ferrero Rocher chocolates, and recovered them for later analysis. At UCC, zoologist Paddy Sleeman has done a preliminary sorting of the little skulls and bones into those of wood mice, Apodemus sylvaticus (field mice, as the Irish know them) and of birds - probably including meadow pipits.
I picked up such pellets once in the wilderness of north-east Greenland, usually beneath a big boulder stained a brilliant orange-red by the lichens fertilised by the owls who perched there. Teased apart, they yielded up myriad fragments of lemming, their jawbones like delicate ivory carvings. So a snowy owl needs to change its diet only a little between a valley in the High Arctic and the tundra-like bits of western Ireland.
But it would not be safe to talk of regular migration, in the manner of, say, the barnacle geese who share the same mix of habitats. Thanks to the incredible thermal insulation engineered by its feathers, right down its toes, the snowy owl is perfectly well able to survive the worst of the dark Arctic winters, even to minus 62.5 degrees Celsius, the lowest temperature recorded in the northern hemisphere. How, in those conditions, it is able to detect and capture the half-dozen lemmings per day it needs to maintain body-weight (these from burrows under hard-frozen snow) remains a mystery. None the less, a good many of the owls do move south in winter, to make problems for airports in Canada and Siberia by chasing mice and voles in long grass.
And in good Arctic "lemming years", which seem to be growing more infrequent, the owls' population explodes, and nomads may then reach as far south as Florida and France.
Sightings in Ireland were once very rare and usually of single birds in autumn, but they have increased in recent years, especially in the north-west. From 1994, a pair of young snowy owls were seen several times in Donegal, and in the summer of 2001 the first-ever nest was found in Glenveagh National Park and monitored by Dúchas staff. Its four eggs failed to hatch, but the event remained, for a time, a momentous secret.
Just as, after long scepticism, visits by walruses to our north-western coast are now accepted as "regular", should we now think of snowy owls as sharing the flyway of migrant geese and waders and even, perhaps, becoming one of our breeding species? They have, after all, made similar beginnings on Fetlar, in the Shetland islands.
On the face of it, the effect of global warming should be all the other way. Among birds new to the Arctic in summer, and spotted by Inuit hunters, have been mallard and pin-tailed duck - even the barn owl. As ice melts and freezes to different cycles, tundra vegetation is already changing and the migrations of geese and caribou are taking different routes (even the sky has changed colour!).
The ecosystem of Arctic wildlife has been both delicate and inflexible, with simple communities and few species, so that the loss of one animal or bird from the system can lead to a cascade of disaster. The kind of radical warming now under way has not been experienced for some 20 million years and many species have no experience of it.
Wholesale changes in tundra vegetation (to thick birch scrub, for example) threaten the lemming particularly, the staple prey of predatory mammals and, of course, the snowy owl. This seems bound to disrupt the behaviour and distribution of an already unpredictable bird. In such unnatural times, we must learn to expect surprises.