Hooo's making that sound? Write it down

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A northern saw-whet owl is photographed near Birds Hill Provincial Park. (CHRISTIAN ARTUSO FOR THE WINNIPEG FREE PRESS)

Christian Artuso stops talking mid-sentence at the sight of an owl swooping along the darkening horizon in Birds Hill Provincial Park.

The goal of this after-hours drive is to listen for the distinctive hoots of half a dozen owls, but glimpsing a long-eared owl in flight is a bonus. Artuso scrambles for an oversized flashlight to see if he can spot the bird again, but it's too late. True to their nature, this owl has already disappeared.

For the past two decades, hundreds of Manitobans have trekked around the province each spring listening for the eery trill of an eastern screech owl, the whistle tone of a northern saw-whet or the calls of four or five other owls native to the province.

"I think part of it is the mystique," said Artuso, whose lifelong fascination with birds led to his job as Bird Studies Canada's Manitoba program manager.

The province's Nocturnal Owl Survey is the oldest in Canada, and the information collected over the past 19 years gives researchers a window into the population health of a mysterious group of airborne predators.

"Most people have a very high affinity or attraction to this charismatic of a bird," said Manitoba Conservation's biodiversity conservation manager, Jim Duncan, who helped start the province's survey with his wife back in 1991.

Duncan credits that charisma with bringing out roughly 600 surveyors over the last two decades: "That, coupled with the ease of identifying calls, and the mystery of getting out there and enjoying Manitoba at night."

The survey, now wrapping up for the year, is timed to the start of the owl breeding season, when they're most vocal.

Surveyors drive along a set route shortly after sunset, stopping every mile or so to listen for an owl's hoot rising above the silence or, later in the season, the croaking of frogs.

All information is compiled at the end of the season and added to the province's database. Last year's 80 or so volunteers covered about 1,200 kilometres and heard more than 140 owl calls.

No owls pipe up over three or four survey stops, although Artuso notes the calls of woodcocks and a thrush, and records the wind levels -- too strong for a good owl night.

Manitoba has 11 owl species, but you'll usually hear just six or seven during the survey due to the rarity, range and breeding season of some birds. Duncan said that limitation makes the survey a draw for people who don't have the training to know hundreds of songbird calls, but could pick out, say, a long-eared or great grey owl.

Owl-tracking is a good way to get an index of the health of different ecosystems, he said. The birds' habitats vary widely: some migrate annually, others every few years, and still others stick close to home.

"It's kind of like a slice of the bird or animal diversity that's out there," he said.

The survey hasn't found any long-term declines, except those officials already knew about, like the low numbers of short-eared owls. Some, like the great horned owl, seem to be holding steady, in part because they can adapt to fragmented ecosystems of treed areas and fields, said Duncan.

"That mosaic is optimal for things like the horned owl," he said.

In the long-term, Artuso fears owls that can't easily adapt to ever-changing environments will suffer, especially Manitoba's boreal species.

"We're increasing our presence on this planet every day," he said.

lindsey.wiebe@freepress.mb.ca

Republished from the Winnipeg Free Press print edition April 30, 2009 B3