Breeding Bird Atlas

Breeding Bird Atlas documents state Ontario's 12 biggest birds by weight are soaring in population compared to 20 years ago.

Everyone recognizes that Canada Geese - one of the big 12 - are plentiful, but the recently published Atlas of the Breeding Birds of Ontario 2001-2005 shows that Bald Eagles, Golden Eagles, Trumpeter Swans, Tundra Swans, Sandhill Cranes and other big birds also are increasing in numbers.

Many factors have contributed to this surge, including banning the use of the pesticide DDT in the 1970s, conservation efforts by various government and non-government agencies, and reduced hunting pressure.

Tundra Swans were nearly extinct in the province and now "they're coming back, nesting all down the Hudson Bay coast and around James Bay," said Mike Cadman, atlas co-ordinator. "Wild Turkeys were extirpated from the province in 1909, reintroduced in the 1980s, and are doing very well now."

Great Blue Herons possibly are scarcer than in 1987, when the first atlas also co-ordinated by Cadman was completed. It may be a statistical anomaly, cautions Cadman. During the first atlas period, special effort was mounted to document heronries, which may have skewed the numbers.

Altogether, 286 bird species were documented as breeding in Ontario during the atlas period. At more than 700 pages, the atlas is stunning, with photos and a detailed, easy-to-read account on each breeding species. Maps show each species' range and distribution.

The atlas was a joint project supported by Bird Studies Canada, Canadian Wildlife Service (Environment Canada), Ontario Ministry of Natural Resources, Ontario Field Ornithologists, and Ontario Nature (formerly Federation of Ontario Naturalists). It involved five years of field research by approximately 2,500 volunteers.

Ontario was divided into a grid of approximately 4,000 squares. Volunteers assigned to one or more squares followed a protocol that combined documenting breeding evidence and conducting point counts to determine both the distribution and an estimate of abundance of Ontario's breeding birds.

"There's an increase in birds of prey - raptors are doing very well," Cadman said, "particularly Bald Eagles, Merlin, Peregrine Falcons." Release programs developed over the past 20 years to help eagles and peregrines are paying off, suggested Cadman. Forest accipiters such as Cooper's Hawks and Sharp-shinned Hawks also are increasing in numbers.

"Generally, owls are up," as well Cadman said, though "interestingly, Great Horned Owls are showing a marked decline. We don't really have a good idea why."

"We're losing grassland birds where forest is coming back," Cadman said, as well as "where agriculture is intensifying." Bobolinks, Upland Sandpiper, Dickcissel, Eastern Meadowlark and Henslow's Sparrows are scarcer.

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"Aerial insectivores - they're way down," Cadman said. "They're all among the 25 species showing the largest declines." This group includes swallows, martins, swifts and nightjars.

Drier summers may be reducing the number of flying insects since many have an aquatic stage in their development, suggests Cadman. "Some birds are migrating earlier, and then whacked by bad weather. Cold snaps in May or June eliminate insects to feed on and the young are vulnerable. Insecticides also may be a factor."

The Oak Ridges Moraine and other areas with increased environmental protection are becoming more forested and forest birds generally are doing well. "It shows up in the Niagara Escarpment, down the Bruce, Grey and Dufferin counties, almost to Hamilton," said Cadman.

"Almost 30 species are expanding their breeding range south, including Yellow-rumped Warbler, Magnolia Warbler, and Hermit Thrush," said Cadman. "About 20 species are expanding their range north," Turkey Vultures, Red-bellied Woodpeckers, Northern Mockingbirds, and Carolina Wrens among them.

The atlas is distributed by Ontario Nature at a cost of $92.50. Call 1-800-440-2366 or see www.birdsontario.org and follow the link to Ontario Nature.

St. Catharines Standard - Ontario, CA.