Montana Audubon

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Snowy Owl

By David Cronenwett

SnowyOwl_Casey2011Because flight enables unfettered movement across vast landscapes and diverse habitats, it is sometimes said that birds remind us of interdependency in nature. Spring and fall migration are much anticipated seasons for birders in Montana since some species occur in our state only briefly during these times. But migration implies a certain predictability and there are many instances when birds end up in unusual locations due to other factors. During winter, many people understandably become enthusiastic when sightings of Snowy Owls (Bubo scandiacus) are reported. These iconic birds, North America’s largest owl by weight, do not arrive in Montana by conventionally understood migratory behavior; they do so because they are nomads.

Snowy Owls are for the most part, strikingly white but females and juveniles tend to possess varying degrees of black or brown “flecking.” Many northern animals are white for at least part of the year, which speaks of their long evolutionary history amidst snow and ice. Snowies are ground nesters that breed on the high Arctic tundra; probably earth’s most intact but imperiled terrestrial ecosystem. They are agile, diurnal hunters capable of plucking songbirds from the air and although they will consume a wide spectrum of animal protein, the great majority of their diet during the summer months consists of a single species; the humble lemming (Lemmus spp.).

To know Snowy Owls and their ecology, including why and how they sometimes end up on our doorstep, we must understand the unique relationship they have with lemmings. These vole-like rodents are known for their dramatic boom and bust cycles as well as a powerful instinct to disperse in large numbers when population density begins to strain resources. Because of this tendency and the lemming’s ability to swim (and occasionally drown while doing so), myths of “mass suicide” still erroneously persist. Regardless, population fluctuations of these creatures hugely affect their Arctic predators, including Snowy Owls who may consume around 1,600 of them annually.

In years of strong lemming reproduction, there is often a corresponding increase in owl hatchlings. However, more predators put more stress on the prey base and competition for it. When this pressure is sensed, the birds will disperse during winter in search of easier food. Because Snowies are adapted to be highly nomadic, it is difficult to generalize about where and when they might appear. A 2008 study found that some individuals actually head farther north, onto the sea ice, possibly in search of pelagic birds in the near total darkness of winter. Others stick close to where they were born and significant numbers head south in search of habitats that resemble the familiar Arctic tundra.

This species holds a special place in the hearts of many birders and in the culture at large as evidenced by their mystical representation in popular films such as the Harry Potter series and more recently, The Big Year. The symbolism of owls generally, across human cultures, is unique. The Chauvet cave system, discovered in 1994 near the river Ardèche in southern France, contains the oldest known Paleolithic art on earth. In its deepest recesses, among the thousands of shamanic images of long extinct beasts, is a representation of an owl, thought to be a Long-Eared, carefully etched into limestone over 30,000 years ago. At Grotte de Bourrouilla in the Pyrenees, the bones of 53 individual Snowy Owls were found intentionally modified, probably for ceremonial purposes, by nomadic hunting peoples near the end of the last glacial maximum. Owls are utterly silent in flight, possess large, intense eyes set into a head that can rotate 180 degrees. When you add the color white, which has archetypal associations with purity, death and the realm of the spirit, this large diurnal raptor instantly becomes worthy of a special reverence. They seem to fulfill the role of “messenger from elsewhere.”

And of course, they do come from a remarkably different world, unlike any most of us can relate to. Alas, it is also a world that is changing exponentially, before our eyes. In many places, the more southerly boreal forest is invading tundra habitats which is certain to displace species unaccustomed to living in those environments. Creatures at the far margins, like those of the Arctic, tend to be more behaviorally specialized which will likely make adaptation to rapid climatic upheaval very difficult. It has already been observed that winters with unpredictable warm spells can melt and then refreeze snow near the ground into an impenetrable ice barrier. This can have widespread and potentially devastating effects on creatures such as lemmings and caribou that must access plants beneath the snowpack.

After years of passively looking for them, I finally spotted a Snowy Owl at Freezeout Lake this November. It was a female, perched atop a pile of riprap not far from the highway. After a few minutes of appropriate gasping, I was overcome with a feeling of how vulnerable this individual bird was as well as the unknown world far to the North, that shaped and gave life to it. There just aren’t simple, feel-good answers to what is happening now, with the chemistry of our planet so fundamentally changed. We may be faced, in our lifetimes, with a profound and tragic loss of Arctic species as well as the human cultures that interacted with them. And who knows how far this will go, since all ecosystems are bound to strain. I begin to think that this white bird represents all of us in a way; life, its adaptations and its limits.

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