The thud of a bird hitting a window is something many Canadian home owners experience. Up until now, little research has been done to document the significant these collisions for Canada's bird populations. A University of Alberta biology class project supervised by researcher Erin Bayne suggests that many birds meet their end in run-ins with Canadian homes.
The U of A students estimate a staggering 22 million birds a year die from colliding with windows of homes across the country.
The research was done in Edmonton and surrounding area using evidence gathered from more than 1,700 homeowners. Homeowners were recruited to become citizen scientists for the study. The citizen scientists were required to complete an online survey where they were asked to recall fatal bird hits over the previous year.
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 vs. 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.
The main factors influencing the frequency of bird -- window collisions were the age of the trees in the yard and whether or not people fed birds.
"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.
"A feeder three to four metres from a window is bad because the bird has space to pickup lots of speed as it leaves the feeder," said Bayne.
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 further are options.
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.
The research was published in the journal Wildlife Research.
- Erin M. Bayne, Corey A. Scobie and Michael Rawson-Clark. Factors influencing the annual risk of bird–window collisions at residential structures in Alberta, Canada. Wildlife Research, 2012 [link]
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