Image copyright Getty Images Image caption Red-winged blackbirds are not afraid to dive-bomb at joggers

Bird attacks on humans are growing more common as people continue to encroach on bird nesting territory, wildlife experts warn.

Mary Heiman was walking her dog around a lake in downtown Denver, Colorado, in late July when a bird started flying uncomfortably close to her head.

Before she knew what was happening, the bird "body slams you in the back of the head, flies around frantically and then goes back in the bush", she told the Denver Post.

"It's funny," she said. "It's just startling when it happens."

Media playback is unsupported on your device Media caption Cyclist 'repeatedly attacked' by Staffordshire bird of prey

Andrea Jones, the director of bird conservation for the California chapter of environmental organisation National Audubon Society, says attacks are definitely rising.

"The increase we're seeing is because we're encroaching on bird habitats. So there are more bird-human interactions," she says.

Most of the incidents arise when birds are trying to raise their young. Nesting birds are very defensive of their chicks - "like a mama bear", she says - and will even attack animals much larger than themselves.

Image copyright Andrea Jones/ Audubon Image caption Andrea Jones studied birds for the Audubon from Massachusetts to California

During Ms Jones' time studying common terns on a beach island in Massachusetts, she was frequently attacked by a noisy dive-bombing squawking swarm, and took to wearing a hat with plastic flowers attached since birds typically attack the highest part of their target.

Ornithologists that study raptors and other birds of prey sometimes wear construction hard hats when checking nests for chicks.

Joggers in Denver, Colorado, have been waving their arms above their heads as they run, in order to prevent their scalps from being strafed by red-winged blackbirds.

It's also a problem outside the US. A man from Prestatyn in Wales was told by his town council to put up umbrellas after he asked the government how to prevent sea gull attacks around his home.

Crow attacks have grown so frequent in Vancouver, British Columbia, that one repeated victim started a website called CrowTrax for people to report violent incidents.

Image copyright Getty Images Image caption Bird attacks rarely look like a Hitchcock film

"Just about everybody has an example of a crow attack," developer Jim O'Leary told the Wall Street Journal. His website has tracked more than 5,000 reports, and he has noticed a slight increase in this past year.

After a postal carrier was repeatedly attacked by a famed crow known as Canuck, Canada Post stopped delivering mail to several homes in Vancouver, citing the danger to its employees.

During Australia's "swooping season" Aussies share tips for how to avoid being attacked by magpie, including wearing an empty tub of ice cream on your head with eyes drawn on in hopes of confusing the birds. Some people glue googly eyes or aluminium strips to their bike helmets to ward off attacks.

Ms Jones from the Audubon says that encounters are more likely to be publicised because of social media reports. But attacks, where birds body-slam or peck at heads, are very unlikely to ever cause injuries to people.

"As long as people respect their space, I don't think there's going to be an epidemic of bird attacks," she says.

Image copyright Getty Images Image caption Humans aren't the only victims - blackbirds, a type of song bird, don't mind attacking hawks or eagles

Climate change is also having an effect towards shrinking bird habitat, she says, as a drought in the US West has dried wetlands where some birds lay eggs and raise chicks.

Experts say that the easiest way to end a bird attack is to simply leave the area of their nest and they will stop bothering you.

And one thing is certain - there's no need to fear the murderous avian swarms as depicted in Alfred Hitchcock's classic horror film The Birds.

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