Toronto, Sep 16 (IANS): As many as 22 million birds are killed in Canada every year after colliding with glass windows, vastly depleting their numbers, a study says.

Objects as seemingly harmless as glass windows are wiping out the birds, according to details unearthed by a biology class project, led by Erin Bayne from the University of Alberta, suggests that many birds meet their end after colliding with window of homes across the country.

The students gathered evidence from more than 1,700 homeowners in Edmonton area, after enlisting them as citizen scientists. Householders also completed an online survey regarding fatal bird hits over the previous year, the journal Wildlife Research reports.

Researchers believe many window collisions are caused by in-flight mistakes. "It's called a panic flight; a bird startled by a cat or competing with other birds at the feeder may suddenly take flight and doesn't recognize the window as a hazard," said Bayne, according to an Alberta statement.

Bayne and his team processed the Edmonton data and concluded that with approximately 300,000 homes in the study area the death toll for birds from window strikes might reach 180,000 per year.

The researchers applied that figure to national housing statistics and arrived at the 22 million figure for bird versus window fatalities. Bayne says that many people recalled bird strikes at their homes, but there was little awareness that residential window deaths might affect bird populations.

"In many cases people who go out of their way to help birds by putting up feeders and bird friendly plants are unwittingly contributing to the problem," said Bayne.

One tip the researchers have for the safer placement of a bird feeder concerns its distance from the house. Bayne says the safety factor has to do with a bird's flying speed. As with car crashes; speed kills.

Fast-flying birds like sparrows and chickadees and aggressive birds like robins are apt to collide with windows placed too close to free food. Placing the feeder either closer or much farther are options.