Canadian crows bring crowded skies

The crows are making life a misery for local residents

Crows - big, black, intelligent and belligerent - are famous for their role in Alfred Hitchcock's horror film The Birds.

And when tens of thousands of them descended on one small town in Canada, it struck fear into the hearts of the local residents.

Around 35,000 people live in Woodstock, 140 kilometres southwest of Toronto.

But a new and mysterious phenomenon called mass crow roosting caused the winged population to, at one point, outnumber the human one.

Woodstock is not the only town to be invaded by the birds

Theresa Carter's house became a no-go zone for almost a month when her back yard was taken over by the birds.

"The sky was literally black," she says. "The trees were just solid with crows - it was unbelievable.

"The noise lasted all night long. You couldn't open your windows, you wouldn't get any sleep. All night long you'd hear them caw caw caw.

Divebomb attacks

"My walkway was on their flight path and they would come straight overhead and literally fill the path with droppings. The odour was unbearable."

Terrified residents also report crows trying to attack them, diving from the treetops.

The birds have caused sleepless nights for Theresa Carter

Woodstock is just the latest town to become host to the mysterious mass roosts. Over the last few years small towns across north America have been plagued by crow roosts of up to 75,000 birds.

"Crow roosting is interesting and I don't think people have it figured out yet," says ornithologist Jody Allair from the nearby Long Point bird observatory.

Humans to blame

"There are a few theories around why crows are roosting in such large numbers. The warmer winters have helped the crows survive the winters a little bit more.

"There's the garbage we leave out and the fact we do supply so much food for these birds. They'd be foolish not to pass it up.

"And it's a pretty ingenious system for crows to take advantage of us."

Experts also blame the invasion on the loss of the birds' natural habitat. Forests are being turned into farmland - forcing the crows to seek new roosting locations in nearby towns and cities.

Ontario's health authority has asked members of the public to report any dead crows they come across because they fear they may be carrying the potentially deadly West Nile virus.

The virus is passed on to birds and humans through infected mosquitoes. Last year it claimed the lives of nine people in the United States.

Infected birds have also been found in Canada but no human cases have been reported.

But the residents of Woodstock do not want to take any chances with their health or their car windscreens.

They are trying to find a way to keep the crows away next year.