BIRD COUNT PUZZLES THE EXPERTS
Friday, February 01 2008 @ 12:53 PM EST
Contributed by: jkr
January 30, 2008 Ontario's eagles are soaring while sparrows fall.
Ontario survey shows steep decline for some songbirds, but trend improving for raptors.
The picture across the province is that eagles and most other big birds of prey are doing well but many smaller species, including swallows and other familiar songbirds, are in steep decline, according to a new edition of The Atlas of the Breeding Birds of Ontario.
Those in trouble are being hurt by urban sprawl, the intensification of agriculture and a mysterious drop in insect populations that might be related to climate change.
"Population trends are generally positive for birds of prey, but biologists are expressing concern about the fate of grassland birds and those that feed on flying insects," says a statement from the organizers of a massive survey that led to the first update of the atlas in 20 years.
The atlas was compiled from five years of observations by 3,000 volunteers, who collected 1.2 million individual bird records from southern Ontario up to Hudson Bay.
The big birds have been helped by the 1970s ban on DDT and other pesticides, says project co-ordinator Mike Cadman.
Bald eagles and other birds of prey had been threatened because the chemicals got into lakes and rivers, tainting fish the birds ate.
The contamination caused deformities and reproductive problems, and also made eggshells so thin they broke apart during incubation.
"Bald eagles have increased four-fold province-wide – even more so in the south – and peregrine falcons are back from the brink (of extinction)," Cadman said.
Those recovering also include three swan species, the sandhill crane, Canada goose and wild turkey.
"Unfortunately, the future seems much bleaker ... for some other species," said Gregor Beck, co-editor of the atlas.
"For grassland species and birds that eat flying insects, the trend is very worrisome."
Populations of some species, including the common nighthawk, whippoorwill, chimney swift and six types of swallow have dropped 30 per cent to 50 per cent in the past two decades. The nighthawk and swift were recently designated as "threatened" species in Canada.
The biggest declines are in southern Ontario, according to those involved in the atlas, including Ontario Nature, Bird Studies Canada and the Ontario Field Ornithologists, along with the federal and provincial governments.
The main threat is the loss of habitat to urban development, roads and intensive agriculture.
A growing problem is the increasing amount of land devoted to corn, for ethanol production, said Caroline Schultz, who heads Ontario Nature.
"We're losing grasslands at a huge rate here."
Grassland birds are also hurt by the province's increasing tree cover, particularly in central Ontario – mainly the result of abandoned farms returning to forest. On the other hand, that change has helped some forest species.
The loss of insect-eating birds might be related to climate change. Bird migrations are timed to the appearance of insects. If warmer weather alters the insects's timing, the birds starve.
"It's a huge worry," said Jon McCracken of Bird Studies Canada.
The survey produced a rough count of birds in the province. The most numerous is the Nashville warbler, with an estimated population of 15 million. The survey estimates a population of 10 million robins.
Eight of the 10 most populous species are in the northern boreal forest and the lowlands around Hudson Bay.
The robin and red-eyed vireo are concentrated in the south.
LINK TO STORY : http://www.thestar.com/sciencetech/article/298660