The short-eared owl, which is primarily seen in southern Ontario in winter, is struggling amid habitat loss and climate change. Can this threatened species be restored to its former abundance?
“That was the firsts one I’d seen in a number of years,” says Cadman, a biologist with the
The short-eared owl is a gifted aerialist renowned for its “moth-like” flight while hunting
Canadian Wildlife Service and coordinator of the Ontario Breeding Bird Atlas project.
The short-eared owl, or “shortie” as birders call it, is a sturdy crow-sized bird with broad, outsized arching wings and a streaky white-brown body. It is a gifted aerialist, renowned for its “moth-like” flight during hunting—stalling, dipping and darting low over the ground. Found on most continents and many oceanic islands, it has the broadest global distribution of any owl.
Yet in 2021 the Committee on the Status of Endangered Wildlife in Canada (COSEWIC) changed the bird’s designation from “special concern” to “threatened” due to the rapid decline of its Canadian population. The loss is estimated at more than 70 percent since 1970, including a 30 percent drop in the past 12 years. “It’s a rare bird in southern Ontario and it’s a big event when one shows up in our area,” says Cadman. “We kept [last winter’s sighting] quiet because we didn’t want floods of photographers going out to harass the bird.”
Meanwhile, 350 kilometres to the east, on Amherst Island in eastern Lake Ontario, Janet Scott tells a different story. The retired schoolteacher, a member of the Kingston Field Naturalists and coordinator of the island’s Christmas Bird Count says she and her spotters recorded “only” 19 short-eared owls in 2021. “In 2020, we got 72,” reports Scott, who has lived on the island, a globally significant Important Bird and Biodiversity Area, since 1984. “That was just one of those years. Every place where there was short grass for hunting voles, [owls] were there.”
Call it a tale of two bird counts. While shortie numbers vary year to year, clearly this species is not rare on Amherst. However, the island’s 70 square kilometres of pastoral landscape is a time capsule of the kind of grassland once common beyond the urban fringe in southern Ontario. This ideal owl habitat is now rare in the province, and the likelihood that its decline will reverse is slim.
In 2020, Amherst Island saw huge numbers of short-eared owls, as seen in this photo by island resident Tina Sawicki.
UNLIKE MANY MIGRATORY BIRD SPECIES that tend to return to the same locations each year, short-eared owls are unpredictable. They may show up in big numbers in a spot one year and be entirely absent the next, probably due to the cyclical abundance of their main prey—meadow voles and lemmings, as well as mice and other small mammals.
This nomadic variability also makes these owls hard to monitor and accurately count. While some birds stay in southern Canada year-round, research suggests that most of the North American population spends the spring and summer breeding season on the tundra throughout the Low Arctic, including around the Hudson and James Bay coasts. In winter, the population’s centre of gravity shifts as the birds seek out grasslands, agricultural fields and wetlands farther south.
Therein lies their biggest threat. Since the middle of the last century, native grassland and wetland habitats in North America have been in steep decline. In western North America, only an estimated 10 to 20 percent of most original grasslands remain, while more than 70 percent of southern Ontario’s wetlands are gone. In the east as well, where much of the original forest was cleared for agriculture, those fields have now been largely taken over by development, abandoned and allowed to grow back into thickets and forest, or modified to support more intensive farming.
Most grassland birds have suffered significant declines as a result. But short-eared owls, while tolerant of people, are especially sensitive to habitat fragmentation. One reason is that shorties are ground nesters (the only such owl species in Ontario), laying their eggs in modest scrapes lined with a few feathers and grass. Not only are these nests easily disturbed, but in a fractured landscape the chicks face an elevated risk of nest predation by raccoons, skunks, coyotes and foxes. While the owl’s northerly breeding areas remain largely intact, the limited suitable land base in southern Ontario and parts of eastern Canada leaves it vulnerable, says Marcel Gahbauer, writer of the 2021 COSEWIC status report. “If anything compromises that, whether it’s lack of prey or further loss of those areas, it makes it that much harder for that regional population to be sustained.”
Gahbauer has a long history with the short-eared owl. A biologist with the Canadian Wildlife Service, he is also the cofounder and executive director of the non-profit Migration Research Foundation. He and two friends established the foundation in 2002, with the short-eared owl as their first focus of study. In the summer of 2003, they visited known locations of historically probable or confirmed breeding activity in Ontario but found only a few birds. “By the end of the summer, we were convinced more than ever that the species was doing poorly in Ontario.”
When compiling population estimates and trends for the assessment, Gahbauer drew on all available sources—the provincial breeding bird atlases, Christmas bird counts, the North American Breeding Bird Survey, and other surveys and atlases—and filtered that through everything he had learned through his own research and that of others in the field. All the datasets tell a similar story, in both Canada and the United States. “There’s a broad understanding and agreement that there’s been a decline and that it’s continuing,” he says.
Cadman and Don Sutherland, a zoologist who recently retired from Ontario’s Natural Heritage Information Centre, have first- hand memories that attest to this decline. Both were teens in Toronto in the early 1970s. Cadman remembers vast areas of fallow land and shorties in abundance in Bramalea, a few kilometres north of Toronto Pearson International Airport: “I’d go out at sunset and watch them flying around.”
Sutherland recalls hay fields in that area that went on “forever,” but also a wrecking yard in the middle of them that was a big wintering area for short-eared owls. “The owls used to roost in these wrecked cars. You could see them sitting on steering wheels and on the seats. I remember there being dozens and dozens of short-eared owls.” Rapid expansion of light industry, warehouses and subdivisions in the area soon put an end to that spectacle.
Local short-eared owl populations are driven by availability of their main prey, meadow voles and lemmings, which typically follow a cycle of scarcity and abundance.
Some of Amherst’s short-eared owls also have a recurring preference for a small group of eastern redcedars growing right next to a house on the island’s north shore. In 2010, Kristen Liptrot, a master’s student at McGill University studying shorties on the island, counted 18 of them roosting one night in the same tree.
According to Scott, that affinity persists to this day. “The trees have grown, but the owls will still roost in there, start- ing in the fall.” The owls even sit near-by, watching with their piercing yellow eyes when the homeowners, Wendy and Richard, have their morning coffee while playing classical music in a sunroom at the back of the house. “Richard tells me he thinks short-eareds prefer Mozart to Beethoven,” says Scott.
Roosting ends in late winter as the birds pair off to mate. Short-eared owls have a relatively brief life span, as little as four years, and begin to mate at one year of age. Researchers believe that most pair bonds last only a single breeding season due to the owls’ nomadic ways.
While renowned for their dancing flight when hunting, the aerial courtship display of the male short-eared owl is uniquely stunning. It begins with the bird ascending in tight circles to a height of between 30 and 150 metres, uttering a low, repetitive hoot, and then diving steeply while clapping its wings under its body as it descends. Such behavioural quirks are why shorties are Scott’s favourite owl. “They’ve got personality,” she says.
“That courtship flight is a remarkable thing to see,” agrees Gahbauer. “I think that’s a function of their habitat. In open country, they can show off by doing that.” It is also a further reminder of how closely the short-eared owl’s fate is linked to protecting open grassland—a challenge that is not as simple as it seems, says Gahbauer. “There are areas like Amherst Island and parts of Prince Edward County where the owls have been breeding more years than not and where some protection of the remaining habitat would [be beneficial]. But because short-eared owls are so mobile and we know so little about where they go, other areas are going to be harder to find.” More knowledge about the species’ populations and movements is needed.
Gahbauer suggests that the urgency of the new “threatened” status of the short- eared owl also be used to raise awareness about the plight of grasslands generally. “I always felt that this was an overlooked conservation issue,” he says. “If we’re transitioning now into broader public awareness of the issue around this bird and others that use similar habitat, then that’s a step in the right direction.”
This article was originally published in the Winter 2022 issue of Ontario Nature’s ON Nature magazine. Photos (from top to bottom) courtesy of: pixabay.com/adriankirby; Tina Sawicki; pixabay.com/Veronika_Andrews.