The little eagle is listed as a vulnerable species in the ACT and NSW but not federally.

Authorities tracked six eagles in 2018-19 using small solar-powered backpacks with GPS trackers attached to the birds.

The most astonishing journey was from an 18-month-old female fledgling, which has been travelling its entire life - flying to Bundaberg in Queensland, then the Gold Coast, then Victoria, then Port Pirie in South Australia, then East Gippsland on the Victorian coast. On Thursday, it started heading north again.

"She visited, like most youngsters, the Gold Coast area. Then she shot across Canberra and basically kept going," ACT environment directorate senior conservation planner Michael Mulvaney said. "She's been in east Gippsland for about the last month. We're expecting for here to return to Canberra... If she doesn't she may have hooked up with someone.

"They're just great flyers, we've got no idea why they want to do these big tours."

One of the males, who lost one of its young to a currawong, took up home in Canberra's industrial areas before flying all the way to Melbourne, also to an industrial area.

Dr Mulvaney said this was perhaps because rabbits weren't controlled in these areas.

Two of the eagles, a male adult and a female fledgling, headed all the way to northern Queensland before turning back when Cyclone Trevor hit Australia. That fledling was only aged four to five months.

One adult male hadn't travelled nearly as far, flying east to the South Coast before spending time at Captain's Flat, and now in Tumbarumba. The remaining adult fledgling travelled to Victoria.

Dr Mulvaney said 60 per cent of their diet was rabbit and 30 per cent rosellas, with big lizards like bearded dragons making up the rest.

"The biggest concern for them has been clearance of their habitat and it was thought they were a fairly specialist woodland bird," Dr Mulvaney said. "We are finding that they are spending a lot of time foraging in rural areas."

Farmland was good ground for rabbits. The birds have a one metre wingspan and weighs less than one kilogram when fully grown, but can only take infant rabbits - kits - rather than adults.

Before Europeans, the eagles ate rabbit-like creatures such as the bandicoot.

Dr Mulvaney said there were nine nesting pairs across the capital in 2018-19. They laid seven eggs but only five successfully hatched.

One was the baby destroyed by a currawong. Another had its nest blown out of a tree during a storm.

There were another four nesting pairs nearby in NSW, producing three chicks.

Twelve little eagles was a small population, Dr Mulvaney said.

"You really want populations of 200," he said.

The tracking program had only been running for about two years, both hot and dry. "It may be we haven't actually experienced them in a good breeding year yet," he said.

The tracking is a joint project between the government, Ginninderry, CSIRO and independent scholars.