A magpie is sitting on a hedge in Sydney. Australians don bicycle helmets with spikes or caps to protect themselves from swooping magpies during the spring season.

AFP/Sydney

Every year in spring, Australians are seen wearing bicycle helmets with spikes on top or caps that have images of eyes on their back. The colourful head gear is not a fashion statement.

Instead, it protects wearers from the swooping magpie, a quintessentially Australian experience where the bird flies low, clacking its beak and sometimes drawing blood by pecking the head of a human victim.

While Australian native animals such as the box jellyfish, funnel web spider and several snake species continue to top the world's most deadly creature lists, the magpie also regularly hits the headlines.

Claire Dunne was cycling in the Hunter Valley north of Sydney in July when she was attacked and chased by a magpie along a road for half a minute.

"Out of nowhere, a bird - I didn't know what it was at the time - was pecking at my helmet," Dunne said.

"It swooped again and again, maybe about four or five times in succession. Because of my helmet, I was fine, and I think because of the position I was in, I couldn't see how big it was, I could just see its shadow.

"I just thought it was ridiculous... I was like, 'I can't believe that just happened'."

Authorities issue warnings every year on how to deal with the magpie season. The southern state of Victoria even offers a "Swoop Off" kit that includes a set of "eyes" that can be printed out and a warning sign that people can display at attack spots.

But while a close encounter with the magpie's black-and-white feathers may evoke memories of Alfred Hitchcock's 1963 film The Birds, experts say its behaviour is misunderstood and people's reactions to its aggression only adds fuel to the fire.

"They're protecting their nest," Robert Johnson of the Australian Veterinary Association said of the birds.

"It's the nesting season in spring, but soon those baby birds will be leaving the nest. And once they've left the nest and can fly away the swooping season finishes."

The months of September and October are the typical nesting - and swooping - season, although magpies can breed across a longer period of time according to the climate in the local region.

The magpie, a medium-sized native bird, measures about 40 centimetres long and is believed to live for up to 30 years.

It is commonly found in urban areas across Australia and tends to nest in tall trees such as eucalyptus and gum, and sometimes in open spaces including parks and playing fields.

The birds' attempts to protect their fledglings has sometimes led to injuries and accidents. In 2010, a 12-year-old boy died after running from a swooping magpie on to a road in Queensland, when he was hit by a car.

More recently, the New South Wales ambulance service said a 12-year-old boy suffered bad cuts to his head after a magpie swooped at him.

The magpiealert.com website, which collects reports of attacks, has recorded more than 1,000 swooping incidents across Australia this year, although only 11% resulted in injuries. Most of those who reported attacks were cyclists.