But there are methods you can use to try and deter a swooping bird, or at least protect yourself from possible injury.

Parks and Conservation urban reserves north area manager Peter Galvin said most tricks were about protecting yourself rather than stopping the bird altogether.

"Once they've started they usually keep that practice up during breeding season," he said.

"The act of swooping, it's a form of protection of the chicks while they're nesting. It usually applies for a six-week period, from when chicks have just hatched to when the chicks leave."

Male birds were the usual culprits during swooping season, which extended from late July to late November.

"During that period some magpies have two clutches," Mr Galvin said.

Associate Professor Phil Gibbons, of ANU's Fenner School of Environment and Sociology, said swooping wasn't testosterone-driven, as previously thought.

"As soon as chicks hatch they enter into this brood defence," he said.

"They will do it against anything they think is a perceived threat."

Professor Gibbons, who was involved in a video by ANU and CSIRO researchers informally testing methods to deter swooping birds, said about 10 per cent of magpies were aggressive towards humans.

Mr Galvin said some magpies could be "quite nasty at times".

"Everything from a scratch right through to an eye being lost or a deep wound on the face," he said.

"All the advice we provide is about helping people to deal with birds swooping and how to protect yourself."

Mr Galvin said cable ties were quite popular tool to deter birds making contact with cyclists' heads.

"[When] a bird swoops a person they go for the highest point," he said.

"With cable ties sticking up the bird doesn't get past that pointy bit. There's not usually any contact with the helmet."

But Professor Gibbons said multiple cable ties didn't deter one magpie involved in his informal testing.

"They just came in lower and aimed at the ear," he said.

Mr Galvin said eyeballing a magpie likely to swoop might deter it from diving towards you.

"In a lot of cases it will be enough to turn them off."

He said many people stuck googly eyes on the back of their helmets so the birds thought they were being watched.

Professor Gibbons said he'd tried the googly eye trick in his swooping experiment but without any luck.

"If you put your hand up they tend to stop or not go for your head - and if you look at them," he said. "Usually, they attack from behind."

An open umbrella is the best protection from an aggressive magpie, Mr Galvin said.

"You're not going to have any injury inflicted on you at all," he said.

"The magpie might make contact with the umbrella, in many cases it will, but that's all it's doing.

"A wide-brimmed hat offers a level of protection but it's not as hard as a bicycle helmet and not as wide as an umbrella."

Mr Galvin and Professor Gibbons advised cyclists to dismount and walk their bicycles through areas populated by swooping magpies.

"If a cyclist is riding...and suddenly the bird makes contact with the helmet they can get a fright and might have an accident," Mr Galvin said.

Professor Gibbons agreed.

"If a magpie is around you should really get off bike or potentially lose your nerve and swerve."

ACT Parks and Conservation rangers install warning signs in areas where one or more birds are known to swoop regularly or aggressively.

Mr Galvin said residents should report magpie problems via Canberra Connect and try and avoid hotspots during swooping season.

"We will erect signs when we have reports of a troublesome bird," Mr Galvin said.

"Take another route if you can."

Swooping hotspots can also be reported to Parks and Conservation via Access Canberra on 13 22 81 or via www.accesscanberra.act.gov.au