They have converged on Canberra's Parliament House in their thousands, sat in the Senate chamber and even set off fire alarms in the building.

They are the swarms of bogong moths, lured every year by the lights of the national capital's largest building.

However this year, the annual bogong migration is looking to set records.

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Linda Broome, who works for the New South Wales Office of Environment and Heritage and has been monitoring the moth for 27 years, says warm weather and strong winds have brought the moths to Canberra much earlier than usual.

"It's certainly going to be a very big year and it's the most I've seen around Canberra for a long while," she said.

The moths breed in the plains of southern Queensland, western New South Wales and Victoria and migrate south to cooler alpine areas - via Canberra.

However, inside Parliament House, they land in your tea, your hair, your handbag and litter office ceilings, walls and windows.

The Department of Parliamentary Services has established a special vacuum-cleaning program to tackle the unwelcome office-mates and has advised staff to close doors and turn out lights.

In this photo, shot with 10-second exposure, seagulls chase the moths, which are attracted to the light. ( ABC: Nick Haggarty )

"Obviously having moths in almost every nook and cranny is an unpleasant thing for many people," DPS Secretary Carol Mills told ABC News Online.

"We have had a number of moths set off our fire alarms, crossing the beams, and so we've had a number of false calls out over the last couple of weeks which is obviously an inconvenience for everybody.

"We've also had a situation where people are quite concerned about work health and safety around food areas and so we prioritise cleaning those places."

Last week, when a second wave of moths hit the House, Ms Mills opted to turn down the lights.

Two people walk through Parliament House as moths sit on the ceiling above. ( ABC: Nick Haggarty )

"For all of the major outdoor areas, the ramps and the external lighting, we turn two thirds of the lights off, so that the remaining light is obviously a lot less and that does seem to help," she said.

"This year we have new lights on the flag pole, we installed new LED lights in July, and people tell me that they are less attractive to the moths.

"But I certainly see the birds flying around at night and think there's still an awful lot of moths near the flag pole."

The birds also chase the moths inside the massive building - a pursuit that led one currawong into the ABC Parliament House bureau last month.

It feasted on its fluttering prey and eventually flew off down a corridor towards the Senate chamber.

Next week, Parliament House will face another invasion - of politicians.

"We're certainly working very hard to make sure that the chambers, particularly for the opening of Parliament, look pristine," Ms Mills said.

"They do get into the Senate area so we've been cleaning there each day."

She hopes the wildlife spectacle will be over by then, anyway - and the focus can return to the usual political spectacle instead.