New Zealand’s Department of Conservation announced Friday that it has stopped a bird-culling operation after hunters mistakenly killed four critically endangered Takahe birds on Motutapu Island. The four flightless birds -- native to New Zealand -- were found on Aug. 17 by conservation staff.

“DOC [Department of Conservation] has put a halt to any future operations to cull pukeko near takahe populations while it conducts its investigation and a review of procedures for such operations,” DOC’s Northern Conservation Services Director Andrew Baucke said, in a statement released Friday. “DOC is currently talking to the deerstalkers involved in the culling operation and the association is cooperating fully with the inquiries.”

The incident occurred when members of New Zealand’s Deerstalkers’ Association were permitted to cull up to 600 pukeko birds -- a highly aggressive bird that is said to pose a serious threat to other native species. Although the pukeko is half the size of the flightless takahe, both species have a similar blue-colored coat of feathers and red beaks.

However, Baucke added, the hunters were carefully briefed on how to tell the difference between the two, and were also instructed to only shoot the birds on the wing.

“Guidelines introduced after an incident on Mana Island seven years ago when another takahe was mistakenly shot during a pukeko cull were also used during last week’s cull,” Baucke said, in the statement. “The deaths are deeply disappointing for DOC and the many groups, like the deerstalkers themselves.”

The takahe was once thought to be extinct, but was rediscovered in 1948. However, despite conservation efforts, the species remains critically endangered, with its current population standing at a mere 300, including about 80 living in the wild.

“I share with the department a concern that the deaths will affect efforts to save an endangered species,” Bill O’Leary, president of the Deerstalkers’ Association said, in a statement released Friday. “I apologize to the department and to the country at large.”