Whenever Snowy Owls turn up in winter in the lower 48 states and southern Canada, they light up social media and rare-bird alerts and may be reported on in newspapers or by local broadcasters. The birds may stay in one place for a while, as one well-documented young Snowy did this winter in New York City’s Central Park, or they may move around. A lot.
A paper published in March in the journal Ornithology 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 Project SNOWstorm, a research effort that studies the species.
The researchers, led by Rebecca McCabe of McGill University, classified 58 percent of the owls as nomadic and 42 percent as “range-resident,” meaning they remained in an area of about 19 square kilometers. Nomadic owls wintered in areas covering more than 200 square kilometers.
A bird’s social status due to age, sex, or body mass did not play a role in whether it stayed put for the winter, the researchers reported. Instead, the deciding factor on whether a bird roamed or not was habitat. Owls in cropland areas tended to stay in one area, likely because those areas have plenty of prey. Birds near water or wetlands tended to move around.
“The Atlantic and Great Lakes coasts represent long, linear habitats with few geographic barriers such as mountain ranges,” writes McCabe. “An owl moving along a coastline encounters an almost endlessly unspooling train of habitat which facilitates long, linear movements in search of food as the water freezes over locally or patchy waterfowl flocks move.”
McCabe and colleagues also note that “different conservation strategies may be warranted” for range-resident and nomadic owls. And they say the survival rates of the two wintering groups warrant further study.