By Dr. Becker
The migration patterns of many birds occur predictably year after year. This isn't the case for snowy owls. While some migrate south year after year, others stay at their breeding grounds or migrate north onto the Arctic sea.
Once in a while, about every four or five years, some snowy owls migrate much farther south than normal in a mysterious phenomenon known as an 'irruption.' During irruptions, the owls, which breed on the Arctic tundra, have been spotted as far south as Florida and Bermuda.1 They've even been seen in Hawaii.
During the winter of 2015 to 2016, an irruption of snowy owls made their way to Michigan's Upper Peninsula, northern Wisconsin and all the way south into Kansas. The Chocolay Raptor Center near Marquette, Michigan had their hands full once the snowy owls began to make an appearance.
Raptor Center Nurses Malnourished Owls Back to Health
In a typical season, the Chocolay Raptor Center sees one snowy owl. Last season, they received six males in October alone. While four of them sadly died within hours, the other two were nursed back to health and let go in November.
Two female snowy owls were later brought to the center; one survived and is expected to be released this spring. By the time such owls reach Michigan, they've made a long flight across Lake Superior. Many are exhausted, weak, malnourished and infested with lice.
Snowy owls are unique in that they like to spend time resting on the ground (unlike eagles and hawks).
If you happen to see one, the Michigan Department of Natural Resources (DNR) recommends observing it from a distance for a couple of hours. If after that time the owl still appears sick or injured, you should notify rescuers.
Snowy owls are protected under U.S. law. Michigan DNR is working with researchers from Project SNOWstorm to research these amazing animals and find out more about their behavior and threats.
Any dead birds found are sent for necropsies. Recently, owls have been found that died of starvation, malnutrition and dehydration, collisions with motor vehicles, electrocution and herpes virus that led to hepatitis and splenitis.2
Controversy Ensues as Airport Officials Shoot Snowy Owls
Snowy owl irruptions present a serious hazard for airports. The owls are used to living and hunting in the wide-open tundras of the Arctic Circle.
When they travel south, the open areas of an airport present a similar landscape. And snowy owls, unlike most owls, are diurnal, which means they're active both day and night.
In 2014, at least nine snowy owls were shot at Gerald R. Ford International Airport in Michigan, while other were also shot at Kennedy International Airport in New York. Ford Airport has a U.S. Fish and Wildlife agency permit that allows it to legally shoot the animals if they're deemed a hazard.3
But the shootings raised controversy over the killing of these magnificent, and protected, animals. Now live traps are in place at Ford Airport. When an owl is trapped, it is relocated at least 50 miles away in the hopes that it won't return to the airport.
Lemmings, Snowy Owls' Favorite Food, May Dictate Irruptions
Snowy owls have a varied diet that includes rabbits, rodents, birds and fish. But their favorite food is lemmings. An adult snowy owl may eat three to five lemmings each day.4 When lemmings are plentiful, owl birth rates may soar, which ultimately means increased competition for food n the Arctic.
As a result, more snowy owls may travel south than normal in search of more food. This was the case during the winter of 2013-14, which Project SNOWstorm described as "the largest irruption in the Northeast and Great Lakes regions perhaps a century."5
In that irruption, snowy owls were reported "as far south as Florida and Bermuda. In 2014-15, another sizeable irruption occurred in the Great Lakes and East, and farther west than the previous year's," according to Project SNOWstorm. They continued:6
"Most people assume that hunger has driven these owls south, and that they are doomed to slowly starve to death in this unfamiliar southern landscape. Both assumptions are generally wrong.It appears it's not hunger that produces these mega-flights, but an absurd abundance of food during the summer breeding season. High populations of lemmings, voles, ptarmigan and other prey lead to large clutches of owl eggs.
There is growing evidence that snowy owls from many parts of the Arctic may congregate to nest in areas where prey is abundant.That happened during the summer of 2013 in northern Quebec, where lemming populations were booming and snowy owls enjoyed a banner nesting season. That autumn, thousands of those young owls moved south.
… Far from starving, most of these Arctic migrants are perfectly healthy – in fact, researchers have found that snowy owls in major irruption years tend to be fatter and heavier than those in non-flight years. Only occasionally do food shortages appear to prompt southerly movements of snowy owls (as happens routinely with species like great gray and northern hawk owls)."
Are Snowy Owls Threatened?
The IUCN Red List of Threatened Species ranks the snowy owl as a species of least concern, and their population in the wild is thought to be large, numbering at about 200,000 owls. However, there are indications that their population is on the decline.
Snowy owls have few natural predators, but they face threats of hunting by native people, which may use the owls for food, feathers and claws. Other threats to snowy owls include electrocution from power lines, airplane strikes, collision with vehicles and entanglement in fishing lines.7 Project SNOWstorm further explained:8
"Not all of the snowy owls that come south in winter will survive, of course – the mortality rate for young raptors of any species is very high. But most will succumb to vehicle collisions, rodenticide poisoning and electrocution on power lines, to name three common causes.
Starvation is fairly rare, and often the result of other, underlying causes, although starving birds are more likely to be found and taken to rehabilitators."