Features
New Atlas Tracks Breeding Birds in Ontario
U of G faculty, staff, students among 3,000 birders who contributed to project
BY ANDREW VOWLES
Climate change may be pushing some birds northward in Ontario, but even more species are extending their nesting ranges in the opposite direction, attracted by growing forests that now cover almost one-third of the southern part of the province.
That's among the surprising facts in the new edition of the Atlas of the Breeding Birds of Ontario, 2001-2005, published early this year. Led by a team based at U of G that involved more than 3,000 birders from Lake Erie to Hudson Bay, the book provides detailed information on where almost 300 bird species nest throughout the province, says Mike Cadman, chief editor and co-ordinator of the five-year atlas project.
“The atlas is a snapshot in time of the distribution of birds,” says Cadman, a biologist with the Canadian Wildlife Service who was based in U of G's Blackwood Hall with the Faculty of Environmental Sciences during the project.
More than that, he says, it's the most authoritative and up-to-date resource on Ontario birds and bird distribution. Following a similar project completed by Cadman and his colleagues in 1985, the new edition contains the first maps of relative abundance in Ontario for many bird species.
That makes the atlas a valuable resource for researchers and environmental managers, says Cadman. Experts can track changes in birds' distribution over two decades, look for what has caused those changes, and recommend management and conservation practices.
For example, some 22 species have shifted their Ontario breeding range northward since the first survey was completed. Scientists think that shift is due to warming conditions that enable birds to forage and nest further north.
Over the same period, however, almost 30 species have expanded their breeding range southward. Comparing the atlas information with land-use data from the Ontario Ministry of Natural Resources (MNR), Cadman suggests that birds' breeding ranges match recent growth in forest cover in the southern part of the province.
By about 1920, settlement and farming had pushed forest cover down to about 10 per cent of southern Ontario's land area. Since then, reforestation has helped that figure bounce back to about 30 per cent.
“People are surprised to learn that,” says Cadman, explaining that it's important to consider not just climate change but also land-use patterns in assessing where things live.
The new atlas includes 286 species breeding in Ontario. That's about the same number recorded by the project in the early 1980s. But not every species is holding its own.
Chimney swifts, six species of swallow and two species of nightjar have declined throughout the province. No one knows what has caused the decline in these aerial bug catchers, but perhaps something is happening to insect populations, says Cadman, who has shared this new information with provincial conservation groups.
Or perhaps land-use changes are affecting these species, just as changing farming practices in Europe have caused a similar decline. One swallow, the purple martin, still lives along the Great Lakes but has largely vanished inland — again for unknown reasons.
The redheaded woodpecker has also seen its nesting range shrink, another eye-opener for Cadman. He says that decline may be linked to the disappearance of dead trees like elms that are the birds' favoured nesting sites.
“We didn't know its distribution would change as drastically,” he says. Other researchers have documented the woodpecker's decline, but “to see the extent of the change on a map like this is quite surprising.”
Besides showing birds' overall breeding ranges, detailed maps in the new book illustrate where species concentrate throughout the province.
The hairy woodpecker, for example, breeds across southern Ontario but is found in greater numbers on the Canadian Shield. Its downy woodpecker cousin also breeds across southern Ontario but prefers the Carolinian forest in the most southerly part of the province.
“That's news,” says Cadman, who notes that the atlas will help agencies set conservation strategies. “Not only are we able to determine which species to put emphasis on but we also know where they are.”
Since 1985, the greatest population declines have occurred in the common nighthawk, chimney swift, bank swallow, blue-winged teal, redheaded woodpecker and barn swallow. The biggest increases have occurred among the Canada goose, house finch, blue-headed vireo, turkey vulture and wild turkey.
Bigger birds account for several of the largest increases, which Cadman links to decreased shooting and reintroduction programs. For these species, “conservation activities are really paying off,” he says.
In more than 700 pages, the atlas discusses these changes in birds' distribution and provides detailed information on Ontario breeding birds. For each species, colour photos and grid maps show range and concentration throughout the province.
Information came from more than 3,000 volunteer birders, including U of G faculty, staff and students, assigned to record sightings during the breeding season.
“They're very keen,” says Cadman, a longtime birdwatcher who studied at Guelph before completing a master's degree at the University of Toronto. “Ontario's birders are renowned for getting involved in ‘citizen science.'”
About 100 people wrote species accounts, including overviews of breeding range and habitat, distribution, population status and history in Ontario. Among Cadman's own contributions to the book was the entry on the bird world's persona non grata.
“No one else wanted to write about the starling,” he says of an introduced species that has followed the spread of human habitation across North America.
Pointing out its range in the atlas, he traces a line across a bare patch that represents Algonquin Park. Starlings avoid most of the park but live along Highway 60 running east-west through the space. The birds even nest at a James Bay radar site located about 200 kilometres from the nearest population centre.
Co-editors of the new book are MNR biologist Donald Sutherland, environmental consultant Gregor Beck, and Bird Studies Canada biologists Denis Lepage and Andrew Couturier.
The atlas is published by Bird Studies Canada, Environment Canada, Ontario Field Ornithologists, the MNR and Ontario Nature.
For more information about the project, including bird maps and data summaries, visit www.birdsontario.org.