A Canadian court Monday held building owners responsible for protecting migrating birds, an environmental group says.

Ecojustice said the court's ruling that the owners of the Cadillac Fairview tower in Toronto had not violated environmental laws was not as important as the greater impact of the decision, the Toronto Star reported. Justice Melvyn Green found the owners, by using a special film on the building's mirrored windows after 800 birds were killed in 2010, had used "due diligence" to comply with the Environmental Protection Act.

Albert Koehl, who represented Ecojustice in the private prosecution, said Green's ruling made it clear owners of similar buildings must take steps to prevent bird deaths. Walls of mirrored glass deceive birds into thinking they have a clear flight path.

"It's not a complete victory, but it's a huge victory," Koehl said. "It means building owners are liable under the law for killing birds with reflective windows. It sends a strong message to building owners that they have to take action."

Fatal Light Awareness Program estimates 1 million birds a year die in collisions with buildings in the Toronto area alone. A municipal ordinance requires all new buildings to take steps to prevent bird strikes.