"They're getting killed everywhere and anywhere where there's even the smallest garage window," Klem said. "In the case of Toronto, perhaps because of the number of buildings and the number of birds, it's more dramatic."

So many birds hit the glass towers of Canada's most populous city that volunteers scour the ground of the financial district for them in the predawn darkness each morning.

They carry paper bags and butterfly nets to rescue injured birds from the impending stampede of pedestrian feet or, all too often, to pick up the bodies of dead ones.

The group behind the bird patrol, the Fatal Light Awareness Programme, known as Flap, estimates up to nine million birds die every year from collisions with buildings in the Toronto area. The group's founder once single-handedly recovered about 500 dead birds in one morning.

Toronto's modern skyline began to rise in the 1960s, giving it a high proportion of glass-clad structures, forming a long wall along the northwestern shore of Lake Ontario. That barrier crosses several major migratory flight paths, the first large structures birds would encounter coming south from the wilderness.

While those factors make Toronto particularly lethal, Klem was also quick to say the city leads North America when it comes to addressing the problem.

After years of conducting rescue and recovery missions and prodding the city to include bird safety in its design code for new buildings, Flap has recently begun using the courts to help keep birds alive.

It is taking part in two legal cases using laws normally meant to protect migratory birds from hunting and industrial hazards to prosecute the owners of two particularly problematic buildings.

The victims are largely songbirds. Perhaps because of familiarity, the urbanites of the bird world - like house sparrows, pigeons and gulls - are much less prone to crashing into glass.

"If the people were colliding with buildings at the same rate birds are, this issue would have been dealt with a long time ago," said Michael Mesure, who co-founded Flap 19 years ago. "There's a detachment in society about this."

One especially effective, if unpopular, method of reducing the threat to birds, Mesure said, is simply to cover the outside of windows up to the height of adjacent trees with the finely perforated plastic film often used to turn transit buses into rolling billboards. The film can be printed with advertising or decorative patterns, although the group has found that a repetitive pattern of small circles made from the same adhesive plastic is both effective and less likely to prompt aesthetic objections.

For new buildings, the solution can be as simple as etching patterns into its glass. A German glass company is also developing windows that it hopes can take advantage of the ability of birds to see ultraviolet light, by including warning patterns that are invisible to humans.

But even after nearly two decades of drawing attention to the problem, Mesure acknowledged that the threat to birds is still rarely considered by architects and developers.

Along the morning search route was a hotel that was one of the last buildings approved before Toronto's new rules took effect. Its extensive use of irregularly shaped reflective glass will most likely make it "quite lethal to birds," Mesure said.