Hundreds of bats were killed in Monday's hailstorm as Canberra's Commonwealth Park colony suffered a significant loss.
ACT Wildlife president Marg Peachey said volunteers from the group had found 322 bats that had died or needed to be euthanised after the destructive storm.
Volunteers worked for seven hours on Monday to treat injured bats that had fallen from trees or had been pelted by hailstones.
"It's a big disaster," Ms Peachey said.
"When we got there they were lying down and the trees were stripped of leaves and branches.
"All of the bats were holding onto those and they just broke off."
Ms Peachey said some bats had been found with golf ball-sized hailstones in their wings. The wildlife carer group had taken 53 bats into care on Monday.
One bat taken into care was only a few hours old.
Grey-headed flying-foxes migrate to Canberra and set up a colony in Commonwealth Park from September to May. Up to 8000 bats have been recorded in the park, which falls under the National Capital Authority's jurisdiction.
Estimates of the number of bats in the park at present have varied from 3000 to 6000.
NCA manager of open space Michelle Jeffrey compared the hailstorm to "hard cannon balls being thrown at them".
She said both adults and pups were among the dead and the death toll was expected to increase in the coming days.
"We're expecting more to perish in the next couple of days," she said.
"They might actually be dead in the trees and fall in the next couple of days."
Ms Jeffrey said there had been significant damage to the tree canopies where the bats reside, which could pose an issue if another heat event should strike.
People should not go to the aid of an injured bat as some carry the deadly lyssavirus.
ACT Wildlife also received about 60 injured birds brought in by vets.
Ms Peachey said the group received 170 calls in the three hours after the hail storm hit. That number is expected to grow today. It normally fielded between 60 and 70 calls a day.
In Commonwealth Park, Ms Jeffrey said other wildlife collected, either dead of injured, included a possum, magpies, galahs and a pee wee.
Wildcare president Belinda Hogarth-Boyd said birds had suffered from concussion in the Queanbeyan Jerrabomberra area.
Her organisation had rescued galahs, rosellas, crested pigeons and cockatoos, which had been blown violently to the ground. They had been taken to a veterinary surgery for observation.