A powerful owl has been spotted in Kinglake National Park for the first time since the Black Saturday bushfires.

The February 2009 fires raged across much of Victoria, killing 173 people and destroying 2,029 homes.

Kinglake was one of the hardest-hit towns, with 42 lives lost and more than 500 homes burned to the ground.

Parks Victoria ranger Tony Fitzgerald, who spotted the owl, said the apex predator's return to the local forest was "the missing piece of the jigsaw".

"These are the last of the top predators to come back," he told ABC Radio Melbourne's Richelle Hunt.

"It's a little bit like the shark is to the ocean; you need these predators to keep the ecosystem in check."

The powerful owl is Australia's largest owl, standing 50 to 60 centimetres tall and with a wingspan of more than a metre.

"They will come down and take a ringtail possum on the wing and grab it off the branch and literally rip it in half with its talons," Mr Fitzgerald said.

Mr Fitzgerald, who has been a park ranger at Kinglake since 1996, estimated there were about a dozen powerful owls living in the national park before Black Saturday.

The Black Saturday bushfires ravaged Kinglake, north-east of Melbourne. ( Daniel Munoz: Reuters )

Watching species return 'a privilege'

He said watching the forest regenerate had been a "fascinating process".

"The shrubs have grown and with them the insects have come again, and with the insects come the animals that eat the insects."

Community volunteers and rangers had noticed lots of ringtail possums while surveying the forest last year, Mr Fitzgerald said.

"The thought was in my mind, 'If there's ringtail possums, the owls surely mustn't be far away'."

He was right — they weren't far away at all.

The powerful owl is Australia's largest owl. ( Supplied: Parks Victoria )

"About a month ago I was out doing some surveying for deer and we find this powerful owl ... having a little bathe."

He said the owl was one of the most exciting things he'd seen in the nine years since the fires.

"It's actually such a privilege to be almost with a front-row seat to see this procession of species come back and create the habitat for other species.

"[Fire] is certainly a destructive force, but nature's been doing this for millions of years and it just kicks the cycle back to zero and starts it over again."