By Ray MacLeod
We have lost 70 per cent of our birds that feed on the wing. In our region of Canada, swallows, nighthawks, swifts, flycatchers and other aerial insectivores are rapidly disappearing and no one knows why.
That shocking news came late last month when a 42-year study by Canada’s leading wildlife agencies was released. The State of Canada’s Birds 2012 (http://www.stateofcanadasbirds.org/index.jsp) raises huge questions about what’s happening to our bird populations and gives few answers. Best guess is that the problem lies somewhere between here and South America.
In general, national numbers have declined 12 per cent since the survey began in 1970. Almost half of Canada’s birds, more than 200 species, showed a population decline, 66 of them so drastic that they are now listed as endangered.
Aerial insectivores “are declining more steeply than any other group of birds, but the causes of the decline are unknown,” the report says. The decline in our zone is the greatest, with birds such as tree swallow and nighthawk now considered endangered. Barn swallow and chimney swift populations are less than one-quarter what they were in 1970.
The Canadian survey dovetails with one by the American Audubon Society, which notes the same species disappearing throughout the eastern United States. According to that study, there appears to be a correlation between the severity of population loss in migratory birds and their wintering grounds. South America is worse than Central America, which in turn is worse than southern North America.
Loss of habitat in wintering areas is also suggested by the Canadians as a possible problem, but not one that likely bears the blame alone. The finger is also pointed at acid rain, as well as the changing nature of our forests, fields and marshlands.
Climate change is thought to be involved and both the Canadian and American surveys suggest more study is needed. For example, little is known about the effect of warming temperatures on insect hatches. As they come north each spring, aerial insectivores time their journeys to the availability of flying food. Once nested, their eggs are hatch when winged insects are expected to peak. What happens if instincts are wrong and climate change has made birds miss those crucial hatches?
Birds that eat flying insect are not the only ones in trouble. Shore birds are in drastic decline, with those from the Arctic heaviest hit.
In addition, birds that live on the marginal bush land between forest and field have a problem.
“Almost 60 per cent of once-common birds that use shrub and forest-edge habitats have declined,” the report says. “This may be due to habitat loss from urban development and maturation of shrub habitats on abandoned agricultural land into forests.”
The State of Canada’s Birds 2012 has fixed a scientific gaze on what wildlife workers like Hope for Wildlife’s Hope Swinimer thought was happening but couldn’t prove. According to Swinimer, knowing for certain that Nova Scotia is losing certain bird species is valued but also frustrating. She says that’s because until the causes are known for certain, nothing can be done about it.
Ray MacLeod is a freelance outdoors journalist. He lives in Waverley.