Every three to five years, hundreds of snowy owls migrate to the Midcoast because of cyclical peaks in breeding success in their Arctic home. (Carol Gray/iStock photo)
It is that time of year again. The change of seasons heralds the arrival of winter visitors and my favorite is a ghost bird, the snowy owl. Whether I spot a bird on a church steeple or cruising over a field, it is a thrill to see these beautiful travelers from the north. My memory retains the long-ago image of my first snowy owl sitting quietly amidst heavy snow.
When naturalist John James Audubon visited Maine in winter and saw snowy owls, he assumed they were breeding in the northern reaches of the state. However, Peter Vickery, in his book “Birds of Maine,” notes that the birds are migrants far from their Arctic breeding grounds. In most years there might be a few dozen owls in our region. Every three to five years we host hundreds of owls, because of cyclical peaks in breeding success in Arctic regions. On those occasions snowy owls have traveled as far south as Bermuda.
Breeding is dependent upon food, especially small mammals such as lemmings and voles. In years with fewer lemmings, we see hungry juvenile owls as early as October. Adult snowy owls arrive here in December or January, returning to Arctic regions in March. Since lemmings are unavailable here, the owls adapt to local prey species, including meadow voles, rats, songbirds, and waterfowl as large as Canada geese.
Among the largest owls worldwide, snowy owls are stunning creatures, with yellow eyes and black beaks. Adult males are almost totally white, while females and juveniles display black banding or spotting. The head is smaller in proportion to the body than other owls’ heads, with only small ear tufts visible on top. Their large feet, with long talons, are feathered, since retaining body heat is critical to winter survival. Owls eat heartily so they can generate and retain adequate body temperature (over 100 degrees Fahrenheit) in severe cold. As with most raptors, females are larger than males, weighing up to 6 pounds.
Snowy owls nest at latitudes above 60 degrees north, in Alaska, Canada, Scandinavia and Russia, favoring open coastal habitats. The female scrapes out a small hollow on top of a mound or ridge with limited nesting material added, or she will use an abandoned eagle’s nest. A clutch of five to 10 eggs will hatch after 32 days. Males and females guard the nest, using aggressive flights or distraction displays, depending upon the size of an approaching predator.
The male does the hunting, searching for rodents, birds, rabbits, snakes and amphibians. He takes food to the nest, where the female feeds the chicks. Snowy owls have exceptional vision and hearing, allowing them to detect prey at long distances. Owls are nearly silent in flight, making them deadly hunters. Prey is normally taken on the ground, but owls may snatch targets in the air or from the surface of lakes and ponds. Prey is swallowed whole or torn apart with the sharp beak. Strong stomach juices digest the flesh, while indigestible materials like bones and hair are regurgitated in large pellets, offering clues to a favored roosting spot.
Given their size and solitary habits, adult snowy owls have few predators. Arctic foxes, wolves, gulls, bears, wolverines and large raptors will snatch owl eggs or immature birds. Occasionally the owls put themselves at risk of airplane strikes by lingering around airport runways, attractive terrain for hunting. While owls are still killed by humans in some regions, the biggest threat to these gorgeous birds would be ecological changes brought on by global warming.
To date there has been only limited study of the owls in their natural habitat. It is now possible to equip captured owls with GPS transmitters that will report on their movements for as long as three years. Scientists have learned that some owls migrate only in Arctic regions, spending the winter in harsh conditions while moving long distances in search of food. It is also clear that snowy owls are capable of hunting at any time of day, and do not share the nocturnal habits of most owl species.
Population numbers are highly speculative for this species, but in 2017, Partners in Flight estimated 100,000 birds in North America, with 200,000 globally. Scientists believe the population is in decline, but snowy owls are currently labeled as vulnerable rather than threatened. We are privileged to host these birds in winter and must hope that efforts to mitigate climate damage will be sufficient to sustain their numbers for the long haul.
Ed Robinson’s latest book, “Nature Notes from Maine Vol. II: Puffins, Black Bears, Raccoons & More,” is available from the Harpswell Heritage Land Trust. All profits support HHLT’s conservation and education efforts.
