Wildlife experts are looking into the death of three endangered Hawaiian crows that were recently released into the wild as part of conservation efforts.

The Department of Lands and Natural Resources (DNLR) in Hawaii reported on Monday, Dec. 26, that three of the five ʻalalās (Corvus hawaiiensis) that were reintroduced into the Pu'u Maka'ala Natural Area Reserve on Dec. 14 were found dead last week.

The Hawaiian crows were part of a breeding program that was supposed to repopulate the islands with the endangered species. ʻAlalās have long been extinct in the wild and are only bred in captivity.

Before discovering the dead ʻalalās, officials said the birds were even spotted doing well and eating from feeders located around the area.

It is still unknown what exactly caused the death of the Hawaiian crows. Animal experts are set to perform necropsies on the dead birds to find out more.

"We were prepared for that possibility," John Vetter, a wildlife biologist at the DLNR, said. "The initial days of release are always the most difficult stage of any release program, and the level of uncertainty is also highest with the first release cohort."

Reintroducing ʻAlalās Into The Wild

Since 2002, populations of ʻalalās have been missing in the wilderness of Hawaii. While attempts were made to reintroduce captive-bred Hawaiian crows into the wild during the 1990s, many of the birds suffered from high mortality rates because of predation and disease.

The DNLR launched the 'alala breeding program in cooperation with the U.S. Fish and Wildlife Service and the non-profit organization San Diego Zoo Global. The Hawaiian crows are part of several bird reintroduction efforts that San Diego Zoo Global has been doing over the past few years.

Christina Simmons, a spokeswoman for the conservation group, said performing full necropsies on the dead 'alalas could take a few weeks to finish. There is also a chance that experts won't be able to find a definitive answer as to what exactly killed the birds.

Bryce Masuda, manager of the bird conservation program, said the loss of the three 'alalas is difficulty for everyone involved in the breeding and reintroduction of the endangered birds into the wild.

He said that condolences for the loss of the Hawaiian crows have come from different parts of the world.

The two remaining 'alalas have now been returned to an outdoor aviary. Vetter said this is to ensure the safety of the endangered birds while they await the result of the necropsies.