Five captive-reared ‘alala, or Hawaiian crow, were released into the wild last week, part of conservationists’ second attempt in the past year to replenish the population of the critically endangered bird in its native habitat.
The two females and three males released Wednesday are part of a group of 11 birds in all released within the past month.
Researchers released a first group, five juvenile males, in December, but three of those birds died within a week. The two that survived were brought back into captivity.
Several changes were made to help the second group fare better.
The birds were released in a different area within the reserve with better road access for researchers monitoring the birds and fewer aerial predators.
They also received more rigorous anti-predator training, which includes reinforcing instinctual behaviors for responding to predators and recreating situations the birds might encounter to “help with an unknown threat,” said Alison Greggor, a behaviorist with San Diego Zoo Global, during a phone interview.
At least two of the birds that died in December likely were killed by an ‘io, or Hawaiian hawk.
As part of the training, ‘alala were played alarm calls with a live ‘io flying over their cage, Greggor said.
“So it was taking them through the sequence of hearing danger, seeing danger and making an association with those social alarm calls and the numerous dangerous stimuli presented to them,” she said.
This second cohort of ‘alala also was mixed-gender, meaning they were “socialized together, familiarized with each other, and more likely to rely on social cues,” Greggor said.
Their release also was timed to avoid peak winter storms.
Researchers say the success of the current release will dictate if and when more birds are released in the future.
“We wouldn’t release the birds if we didn’t think we had done the best we could at this point,” Greggor said. “So at this point there are risks and challenges ahead, but we can agree we’ve done the best we can for these birds going forward.”
‘Alala have been extinct in the wild since 2002.
Reintroduction efforts are funded by the state Department of Land and Natural Resources, San Diego Zoo Global and the U.S. Fish and Wildlife Services.
Email Kirsten Johnson at kjohnson@hawaiitribune-herald.com.