Populations of burrowing owls have declined by more than 90% since the 1990s, and the species was listed as endangered in June 2003.
Some of the challenges facing the species are roads, conversion of native prairie to crop, a decline in mammals that dig burrows the owls live in and a different community of predators. One such predator is the Great Horned Owl, which weren’t found on the prairie until there were structures – abandoned buildings, power poles, old gas wells and fence posts – for them to perch on to hunt.
“Ultimately, the prairies are a different place than they were in the past,” stated Graham Dixon-MacCallum, population ecologist with the Wilder Institute and Calgary Zoo. “Burrowing owls are from a different time, they love that flat, wide open prairie between Medicine Hat and Brooks.”
Burrowing owls not only need burrows, which they use to nest in and seek shelter, in southeast Alberta, but also between Alberta and Mexico, where they spend the winter, resulting in migration becoming increasingly difficult.
Nestlings are the least likely to survive and that is the reason the Wilder Institute has chosen to focus on this age range since 2016 with much of the work being done in the Suffield area. The nestlings are captured and placed under human care from about late July of one year until spring of the following year.
“We are really fortunate at the Wilder Institute that we aren’t doing this work alone,” explained Dixon-MacCallum. “We do these releases on CFB Suffield and on privately managed ranches in the Suffield area and we couldn’t do this work without those local ranchers. Burrowing owls like areas that are grazed so working with cattle ranches is really important for us because those pastures make for great habitat for burrowing owls.”
Researchers start out by finding nests and then monitoring them. Burrowing owls fledge from the nest when they are around 35 days old. In July, when the owls are between 20 to 35 days old, a one-way trap is installed at the entrance to a burrow. Once captured, each owl receives a unique leg band so researchers can differentiate one from the other.
Since 2016, the Wilder Institute has trapped hundreds of owls and have not observed any ill effects from the trapping method used.
“The methods we are using were developed by people who have been studying and trapping burrowing owls for decades, we are able to rely on the expertise of people who have come before us and have trained us and the agencies that give us permits with the provincial and federal governments who are also approving the protocols we use,” stated Dixon-MacCallum.
The nest sites are visited every week or two so researchers can collect data on when they lay eggs, when the eggs hatch and when the owls come above ground.
Only 6% of nestlings would return to Alberta to nest the following year without human intervention.
As Dixon-MacCallum explained, “We keep them in care throughout that period of really low returns and then we encourage them to be back nesting in Alberta the next year.”
Early in May, 26 owls were released back into the wild in the Suffield area, 12 male-female pairs and two individual females. Dixon-MacCallum said the burrowing owls are doing well post release and throughout the breeding season, although migration still remains a challenge. The field crew is currently out surveying for owls and keeping an eye on the ones recently released and will be bringing another cohort into human care this coming July.
By SAMANTHA JOHNSON, Local Journalism Initiative Reporter
Original Published on May 16, 2023 at 08:40