Whenever snowy owls appear in the lower 48 states and southern Canada during winter, they will light up on social media and on rare bird warnings, and may be featured in newspapers or local broadcasters. The birds can stay in one place for a while, as a well-documented young Snowy did in New York’s Central Park this winter, or they can move around. A lot of.
An article published in March in Ornithology magazine tracked the movements of 50 snowies that were tagged with GPS transmitters in eastern and central North America from 2013 to 2019 as part of the SNOWstorm project, research to study the species.
The researchers, led by Rebecca McCabe of McGill University, rated 58 percent of the owls as nomads and 42 percent as “range resident,” meaning they stayed in an area of about 19 square kilometers. Nomadic owls wintered on more than 200 square kilometers.
A bird’s social status based on age, gender, or body mass didn’t matter whether it stopped for the winter, the researchers reported. Instead, the determining factor in whether a bird roamed or not was habitat. Owls in farmland areas tended to stay in one area, probably because those areas have abundant prey. Birds near water or wetlands tended to move.
“The coasts of the Atlantic and Great Lakes are long, linear habitats with few geographic barriers like mountain ranges,” writes McCabe. “An owl moving along a coast encounters an almost endlessly decoupled habitat train that enables long, linear movements in search of food when the water freezes over locally or when spotty flocks of waterbirds move.”
McCabe and colleagues also note that “different protection strategies for resident owls and nomads may be justified”. And they say the survival rates of the two wintering groups warrant further investigation.
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