A pair of critically endangered western ground parrots was lucky to have been captured by wildlife officers just moments before a major bushfire swept through their habitat in Western Australia's south.

The male and female were netted in Cape Arid National Park to take part in the captive breeding program at Perth Zoo on Tuesday, just as a blaze that was sparked by lightning two days earlier became a possible threat to lives and homes.

A watch and act alert was issued and the park was evacuated.

Department of Parks and Wildlife officers were about to grab a second pair of parrots when they had to leave.

"We had just started that work when we were told to get out of there," regional ecologist Sarah Comer told AAP.

"Those two are probably quite lucky.

"It was a very good move, moving us on."

Ms Comer, who along with rest of the department's officers in the region are now fighting the fires, said there were only about 140 of the vulnerable, ground-dwelling birds in the park the last time they estimated numbers.

She said it was hard to be exact as the cryptic, near-flightless animals were difficult to monitor, so wildlife officers roughly counted their calls as they left to feed and returned to roost.

Introduced predators are normally enough to contend with, but the park's parrots had already endured a big fire last month when the latest blazed through.

Ms Comer said it was too early to tell how much of their habitat had been destroyed, but it wasn't looking good.

"We're doing our best to keep it to the smallest possible area in that critical habitat.

"We know it's bad but we need to just wait and then get out there and have a look at what's happened.

"We're going to end up with a very large fire scar at the end of the day."

Crews are having to adopt strict hygiene practices in battling the fire as the park is one of the few remaining areas of that size in the state that is dieback-free.