WASHINGTON, February 6, 2014—The story of a snowy owl injured after being hit by a D.C. bus last week saddened those who had delighted in spotting it around the city. Generally spending much of their lives in the Arctic tundra, a massive southern migration of snowy owls this winter is pleasing birdwatchers and puzzling ornithologists.
While the southern migration of a number of snowy owls is not unusual, this year has been a record-breaking one, with individuals spotted along the East Coast as far down as Jacksonville, Florida and even one owl spotted in Bermuda.
With a wingspan of over five feet, snowy owls are large enough to cause a problem for pilots. To prevent bird strikes, many of the nation’s airports have catch-and–release programs. Smaller airports shoot firecrackers and employ other tactics to scare the birds away when they get too close.
The count of snowy owls caught at some airports is indicative of just how many snowy owls are migrating south this winter. For example, Boston’s Logan International Airport has caught a record 80 snowy owls, and the season is not over yet.
“An average year at Logan Airport, we remove six to eight snowy owls a winter,” said Norman Smith, director at the Massachusetts Audubon society to the New York Times.
Other airports are not quite as kind. New York Port Authority “wildlife specialists” shot and killed at least three snowy owls near JFK Airport Saturday, causing public outcry. The agency announced Monday that it would no longer kill the animals but instead implement a catch-and-release program.
Ornithologists believe that the owls are attracted to airports because they are large, flat, treeless expanses, resembling the Arctic tundra where the owls live most of the year. As native grasslands and undisturbed expanses have given way to development, airports attract more snowy owls because they are some of the only such places remaining.
While there are many theories as to why this year’s migration is so large, nobody knows for sure.
With cyclical populations linked to the abundance of prey, some experts believe that higher owl populations are directly related to a boom in the population of lemmings, the small rodents that make up a considerable portion of the snowy owls’ diet.
Snowy owls are one of the few birds that can vary the number of eggs they lay depending on the abundance of food. Under normal conditions, a snowy owl lays a clutch of three to five eggs every year. Snowy owls can also skip a breeding season when food is scarce. However, if food is plentiful, snowy owls will lay up to nine eggs. This year’s high lemming population is thought to have promoted a higher than usual snowy owl population.
As extremely territorial birds, when population goes up and food becomes scarce, juveniles are often forced out of their territory and must fly further in search of food. Most of the owls spotted in the lower states have been juveniles, seemingly supporting this theory.
Others believe the answer may be more complicated. Bird movements and population numbers can represent a bellwether, often offering one of the earliest signals of damage or change to an ecosystem.
“These owls are surely telling us something, but we still don’t understand exactly what,” says eBird, a snowy owl tracking website created by the National Audubon Society and Cornell University’s department of ornithology. “It could be that this is a large invasion that is part of periodic and natural fluctuations; or an unsettled Arctic environment could be part of the story.”
While climate is certainly changing in the Arctic, with shrinking sea ice, changes in snowfall totals in the winter and record-setting heat in summer, it is unknown whether and if this is affecting snowy owls. Researchers do not know, for example, whether changing Arctic climate is affecting lemming populations, and how this affects snowy owls.
Some suggest that shrinking sea ice may affect snowy owls’ ability to hunt water birds, another major source of food. Kevin J. McGowan, an ornithologist at Cornell University who tracks snowy owls with transmitters, has observed that instead of flying south during winter, many snowy owls instead fly further north looking for sea ducks and other water birds in Arctic pools of open water.
It is unknown how water birds are reacting to the steady decrease in sea ice; some say they may congregate near the ice edge, while others think that the sea ice decrease will force the waterfowl to migrate south. It is unknown what a change in either direction means for the owls, their migration or their numbers.
eBird urges those who spot a snowy owl to be respectful of the bird and watch from a distance. They also urge those who see a snowy owl to enter their location and picture in their online tracker, to better understand these birds and their movements.
Considering the innumerable connections between species and their habitat, especially in fragile ecosystems like the Arctic, could the snowy owl be the proverbial canary in the coalmine?