More than 1958 eastern grey kangaroos will be shot while parks are closed in the evenings from Sunday to Thursday.

ACT Parks and Conservation is responsible for the program, designed to control overpopulation, which threatens grassland sites due to overgrazing.

Executive manager Justin Foley said although the grass is green due to recent rain, the ecosystem was still fragile.

"The animals that rely on the grasses for food, shelter and breeding purposes, including several endangered species, are still recovering from extended hot and dry conditions," Mr Foley said.

"Nobody likes shooting kangaroos, however, we accept it's the most humane method of kangaroo population management available to the ACT government as a responsible land manager."

An ACT government spokesman told the Canberra Times in January ecologists would evaluate if a cull was needed this winter in the wake of the Orroral Valley fire.

The cull, which normally begins in early May, was delayed until June 15 while an assessment was made, which considered numbers lost in Namadgi National Park and Tidbinbilla Nature Reserve during the bushfires.

Mr Foley said while the cull had been reduced from a record 4035 in 2019, populations had been deemed unsustainable in urban reserves.

"Whilst we have had fires and we have seen droughts we are still seeing high numbers in our urban reserves and significantly higher than our urban reserves are able to support," he said.

Mr Foley said high populations were putting significant pressure on grasslands and grassy ecosystems.

"Canberra is, if you like, the perfect place for a kangaroo to live as we have lots of grassy ecosystems and we don't have predators in the ecosystems," he said.

He said the kangaroos seemed to have a preference for the native species of grass which grow in the nine reserves where the cull will take place.

He said they favoured the green shoots which meant they were eating the grass down to the ground, making way for weeds and invasive species and causing erosion.

"We hope the community will understand that the conservation cull is vital for the wellbeing of the environment," Mr Foley said.

"We do value the kangaroo and what we're trying to do is get a system that's functioning as well as possible. We're limiting numbers so they're not expanding at the expense of other systems and the rest of the ecosystem."

He said the grasslands were home to a number of native species, including the grassland earless dragon, striped legless lizard, pink-tailed worm lizard, Perunga grasshopper, hooded robin and brown treecreeper.

Mr Foley said animal welfare was of the utmost importance to the Parks team and the current cull was going ahead accordingly.

"It's been safe. It's been conducted according to best practice and we believe we're achieving our outcomes," he said.

While members of the public had been present in closed reserves on a small number of occasions, no infringement notices had been issued, according to a government spokesperson.

Sites will reopen from August 1 or earlier if the program is completed sooner.