The Scientific Lives and Irresistible Irruptions of Snowy Owls
Harry Potter’s Snowy Owl, Hedwig, logged thousands of miles delivering mail and packages for him, although her journeys were not called irruptions, and she also accompanied him in his travels and battles against Voldemort. Traveling like Hedwig, Snowy Owls sometimes fly thousands of miles away from their home in the Arctic in migrations called irruptions. Every winter a portion of the Snowy Owl population flies south from their breeding grounds in the Arctic, but every three or four years or so thousands of them fly far to the south to create a Southern Irruption.
Why Do Snowy Owls Irrupt?
Snowy Owl irruptions often coincide with fluctuations of lemming populations in the Arctic. When Arctic lemming populations decrease, Snowy Owls migrate south to find food. When the lemming populations surge, Snowy Owls produce multiple chicks that migrate south when they mature, regardless of lemming numbers Wildlife biologists like Brian Roell of the Michigan Department of Natural Resources explain that the migratory patterns of Snowy Owls depend on the availability of food, but there are few if any studies tracking how many Snowy Owls travel back and forth from summer and winter habitats.
Scientists believe that irruptions coincide with wide fluctuations in the breeding cycles of lemmings which make up about 90 percent of the main diet of snowy owls. Other factors like weather and numbers of owl hatchlings may also affect irruptions.
Scientists speculate that the booming Snowy Owl population of 2011-2012 may have driven mostly younger, male owls much farther south than usual and some also speculate that a sizeable decline in lemming populations after a boom could have led to the 20111-2012 Snowy Owl irruption.
During the Southern Irruption of 2011-2012, thousands of Snowy Owls flew thousands of miles from their home in the Arctic to several of the United States and most of the Canadian Provinces. Thousands of Snowy Owls have fed in Idaho farmlands, roosted on Montana rooftops, glided over Missouri golf courses, and soared over Massachusetts shorelines.
Denver Holt of the Owl Research Institute in Charlo, Montana who has studied Snowy Owls on the Arctic tundra for at least two decades described the 2011-2012 irruption as “unbelievable.” He said that the huge increase in the amount of Snowy Owls in the 2011-2012 irruption remains a mystery. “We do know they had a really good breeding year, and there was plenty of food last year. Instead of no chicks, or one or two, a single nest will produce five, six, seven or more fledglings in a good breeding year.”
According to Denver Holt, the 2011-2012 Snowy Owl outbreak over multiple states and countries is a mystery characterized by much speculation and little hard evidence as to its causes and effects. He said that Snowy Owl populations are in overall decline, possibly because climate change has inhibited the growth of vegetation and grasses that are the chief food supply of lemmings.
Mass Owl Sightings in Southern Irruption Year 2011-2012
Normally, Snowy Owls live in the United States Fish and Wildlife Service’s Arctic National Wildlife Refuge and in other locations north of the Brooks Range in Alaska. They summer in the far north and in winter they migrate into southern Canada and some even spend winters in the Northern Plains and New England. In the fall of 2011 they surged across the United States in large numbers and in the winter of 2011-2012, Snowy Owls were sighted in Pennsylvania, Indiana, Minnesota, Michigan, and Wisconsin where at least 100 arrived. They also appeared in Kansas, Oregon, Texas, Washington, most Canadian provinces, and even Hawaii.
The Snowy Owls materialized in both urban and suburban locations across United States and Canadian Provinces, appearing along highways, perched on signs, fence posts, and buildings. Snowy Owls tend to congregate in airports, including Logan Airport in Boston, because airfields look like tundra to them. Airport personnel trap and remove them and occasionally shoot them.
Owl Research Institute’s Denver Holt said that Federal officials shot a Snowy Owl who landed at a Hawaii airport on Thanksgiving Day 2011 because they were afraid that the Snowy Owl would interfere with airplane traffic.
Results of the 2011-2012 Southern Irruption
A story published in the Northern Light in Blaine, Washington in November 2012 reported snowy owls were sighted in Blaine, the second year in a row they have returned even though the 2011-2012 irruption officially ended in April 2012. One of the Snowy Owls perched on an apartment building chimney as if posing for photographs and delighted both residents of the building and people walking past.
A citizen science group, eBird has made the 2011-2012 Snowy Owl irruption one of the best recorded irruptions in history. Run by the Cornell University Ornithology Lab and the Audubon Society, eBird is based at Cornell University in New York. Bird watchers across America call in Snowy Owl sightings and workers plot them on a map that shows the exact spots where the birds winter. They gather data about Snowy Owls and serve as a source of information about them.
Spotlighting Snowy Owls
When they are not irrupting, Snowy Owls live in the arctic tundra, in North America, Europe, and Asia and a small number breed in the northern British Isles. In the younger days of the earth when the Arctic climate extended farther south than it does now, Snowy Owls lived much farther south.
One of the largest breeds of owls, Snowy Owls take their name from their white coloring. Weighing about four pounds, Snowy Owls are the heaviest owls in North America and they grow to be about 24 inches tall with an average wingspan of from 4.2 to 4.8 feet. The males are pure white, while females have dark patches of plumage and the male is slightly smaller than the female. Adult males grow whiter as they age, but females retain their brown markings. The Snowy Owl’s feet are covered with feathers and they are thickly padded.
Snowy Owls have excellent vision using their round, yellow eyes like binoculars. From high in the sky they silently swoop to earth to capture rodents, and smaller birds. They see equally well at night and they are both nocturnal and diurnal, hunting during the day and at night. In the summertime Arctic, daylight lasts 24 hours so Snowy Owls hunt in the daylight too.
Since they are predators, Snowy Owls eat only animals and not plants. Lemmings, fierce little rodents smaller than chipmunks, are their prey of choice. When lemmings are plentiful, Snowy Owls eat mainly lemmings. They can eat at least three lemmings a day, or about 1,600 a year. When lemmings are less plentiful, Snowy Owls look to other animals for food. Depending on where they live, Snowy Owls eat snowshoe hares, grebes, ducks, ptarmigans, ground squirrels, rats, partridge and even fish.
Wildlife biologist Brian Roell says that they depend mainly on small rodents, but they will eat medium sized birds like gulls, ducks, and geese as well. They swallow their food whole or tear it into large pieces to make it easier to eat. Observers have seen Snowy Owls washing their faces in the snow to remove leftover parts of their meal.
Snowy Owls build their nests on the ground and both the male and female care for the owlets. Both owls will fiercely defend their nest, even from wolves. By the time they are eight weeks old, the owlets are ready to leave the nest. This is a necessary milestone because of the short Arctic summers. If they aren’t ready to care for themselves in two months, the owlets will not survive the cold winter. Many of the migrating Snow Owls are young males looking for new territory.
Since they are birds of open land, Snowy Owls tend to perch on high points that overlook open spaces including beaches and airports. They choose a lamp post or rooftop, but seldom perch in a tree. Many of them choose airports to roost. Biologist Brian Roell believes that Snowy Owls enjoy roosting near or at airports “because airports mimic their normal treeless habitat.”
Snowy Owls and People Precautions
According to Charles Sindelar, Jr. in A Comparison of Five Snowy Owl Invasions in Wisconsin, Snowy Owls who migrate aren’t necessarily suffering from starvation or disease. Some will die from the rigors of the migration from the Arctic regions and others will fatally encounter electric lines, vehicles and other hazards as they travel. Sometimes Snow Owls create problems for themselves with humans by preying on domestic birds. Some of them starve to death.
Ornithologists and researchers share important cautions to people about their interaction with Snowy Owls. The birds are already stressed because of a lack of food. People observed one of the southeastern Wisconsin Snowy Owls in Ozaukee County and then a few days later a farmer found the Owl dead. Closer examination revealed that the Owl was extremely emaciated and probably had starved to death. Life can often be difficult for Snowy Owls and people keeping a good distance and not disturbing them can be the best way to help them
Since they come from wild spaces, Snowy Owls have no innate fear of humans and will allow people to get very close to them. Wildlife professionals advise people to give Snowy Owls plenty of space. A good rule of thumb is that if the Snowy Owl is repeatedly looking at you, you are too close! Using your car as a blind is a good option if you want to observe or photograph them. Using live mice to lure Snowy Owls to roadsides to photograph them is a terrible idea. Exposing them can attract the attention of nearby crows, causing harmful mobbing of the Owl.
The goal of Snowy Owl well wishers is for them to survive the winter away from their distant home and then return to the tundra to breed the next spring. The Federal Migratory Bird Act protects Snowy Owls in the United States and they are the state bird of Quebec.
Snowy Owls and People Have a Deep Connection
A cave wall in Ariege, France, features an outline of two Snowy Owls and their chicks that Paleolithic artists painstakingly etched. This prehistoric drawing makes the Snowy Owl one of the first recognizable birds to be drawn anywhere in the world. Owls, including Snowy Owls, have had an important influence on human culture, appearing in the mythology of many nations. Romanians believed that the souls of repentant sinners flew to heaven in the shape of Snowy Owls. In Russia, hunters carried owl claws so that if they were killed their soul could use them to climb up to heaven. In many Mediterranean countries owls were considered symbols of bad luck, but in Mongolia people hung up owl skins on their doors to ward off back luck.
In Harry Potter’s wizarding world, Hedwig, Harry’s Snowy Owl, is a creature from yet another world, but she became his pet, companion, and trusted friend who gave her life defending him. Their complicated relationship is much like the one between humans and Snowy Owls.
Shelford (1945) discusses the possible relationship between lemming cycles and Snowy Owl invasions.
Kerlinger et al. (1985) give some alternate ideas about what causes these irruptions (Kerlinger, P., M. R. Lein, and B. J. Sevick. 1985. Distribution and population fluctuations of wintering Snowy Owls (Nyctea scandiaca) in North America. Can. J. Zool. 63: 1829-1834)
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