Saturday, December 29, 2012

Snowy Owls

Among the most easily identified birds on our planet, snowy owls breed on the Arctic tundra of Alaska, Canada and Eurasia.  Their dense plumage makes them the heaviest owls in North America and their wingspan may reach 5 feet.  Adult males are almost pure white with scattered, small black markings while females have black edging on their feathers; juveniles have more extensive black barring.  Snowy owls have black beaks, yellow eyes and small ear tufts that lie flat against their rounded head.

These Arctic owls feed primarily on lemmings and their population tends to fluctuate with the availability of that prey; on their breeding territory, they also hunt other small rodents and ptarmigan.  Nests are shallow depressions on the ground (usually on a low rise for visibility and dryness) and both parents cooperate in raising the young; depending upon food abundance, 3 to 12 eggs are produced.  While adults are apex predators and rarely threatened, young snowy owls are potential prey for gray wolves, arctic fox, golden eagles, skuas and gyrfalcons.

As the perpetual sunshine of the Arctic summer begins to wane, snowy owls head for wintering areas as far south as the Northern Plains and New England.  Like short-eared owls, they favor open areas, including prairie, ranchlands, broad floodplains, airports and coastal dunes and are active during the day.  Hunting from a low hill or fencepost, they may sit for hours at a time, springing into flight when prey is spotted.  Winter prey is highly variable and these owls are opportunists, taking small mammals, waterfowl, pheasant, quail, gulls and songbirds.  Veteran birders know that snowy owls are an irruptive species and look forward to their seasonal incursions; their winter population in the lower 48 varies widely from year to year and, during large irruptions, individuals have been found as far south as the Gulf Coastal Plain.