Winter is growing old and the reports of spring migrants are beginning to trickle in to the birding hotline. There are also some interesting winter visitors still hanging around, offering some lucky birders great viewing opportunities.

First, the returning migrants.

Turkey vultures, red-winged blackbirds, common grackles, and eastern bluebirds have been reported in the southern part of the state. A friend of mine opened his door to an invasion of purple finches in his yard in Orono; elsewhere, another birding friend, Ed Grew, spotted the first killdeer at the Witter Farm fields as well as a male wood duck on the ice in the Stillwater River.

Pine siskins, juncos, and even song sparrows have been seen, as well as an American woodcock. A merlin was heard calling from a tree in the middle of Bangor, robins are increasing, and white-throated sparrows are arriving.

Our winter stragglers – birds that usually remain on or very near their breeding grounds all winter long but that occasionally “irrupt” into southern areas – are still being spotted. These include snow buntings, northern shrikes, and, the greatest of them all, a Queen (or King) of the North: the snowy owl.

There are a few characteristics that set this owl apart from other owls. It breeds in the high Arctic – “the land of the midnight sun” – so it needs to be able to hunt equally well during the day as it does at night at other times of the year.

It nests beyond the tree line on the open tundra, far from any substantial protective cover. Consequently, it is a fierce defender of its eggs and young; researchers have observed snowy owls divebombing arctic foxes and arctic wolves, successfully driving these large mammalian predators away from the nest. In fact, snowys are so adept at defense that other birds, such as the snow goose, will nest near them for protection.

Now, snowy owls – our heaviest North American owl if not the longest in length – have been known to make a meal of a goose. But for some reason they seldom take prey in close proximity to their nests. How the geese know this is one of those unfathomable, fascinating mysteries of nature.

The only main predator of the snowy owl is the human. The owls will attack and inflict injuries on people who approach their nests, striking from behind with their talons either extended or balled up into fists.

This bird is serious stuff. However, on their wintering grounds, they are either timid or very docile toward people.

Traditional theory held that snowys “irrupted” from their normal ranges in response to the population crash of their favored prey, the lemming. David F. Parmelee, writing for “The Birds of North America” species account, says that the relationship between snowfall amounts and temperature conditions may also be a major factor.

Each winter, snowy owls will seek out more southerly habitats that most closely resemble their breeding grounds: bare, open country. They are typically spotted as they perch atop a sand dune, fence post, boulder, hay bale, or barn roof in a “sit and wait” strategy of hunting.

These visitors from the far north have always fascinated me. Something has captured my imagination even further, adding an extraordinary dimension to these already intriguing birds.

Sometime during the last Ice Age, in the region now called France, a Paleolithic hunter-gatherer etched the outline of a pair of snowy owls and their chicks into a cave wall. This makes the bird, according to Permelee, “evidently … the oldest bird species recognizable in prehistoric cave art.”

Somehow this is fitting for this ghostly Spirit of the North.

Speaking of owls

Maine Audubon is seeking volunteers from around the state for the Maine Owl Monitoring project. If you are interested in participating, please call Susan Gallo at (207) 781-2330, ext. 216, or sgallo@maineaudubon.org. I will be conducting a survey myself, so look for that in an upcoming column.

BDN bird columnist Chris Corio can be reached at bdnsports@bangordailynews.net