Sihek also known as the Guam kingfisher. Photo: Supplied / John Ewen
Nine sihek, also known as the Guam Kingfisher, are now living in the wild in the tropical forests of Palmyra Atoll, a conservation site that is 1000 miles south of Hawaii.
"It's probably one of the best protected places on Earth. While it was heavily disturbed during World War Two, it is now an incredibly healthy ecosystem," The Nature Conservancy's Alex Wegmann said.
Wegmann is part of a wider team helping to restore the sihek population which he said was about 140 birds worldwide - most remain in human care at various Zoos in North America.
Sihek were taken from Guam to the US into captivity, in efforts to save them from being wiped out by the brown tree snake which has overrun the territory.
The sihek recovery program is working to establish a temporary wild population on the American island Palmyra Atoll before their eventual return to Guam.
Sihek also known as the Guam kingfisher. Photo: Supplied / John Ewen
It marks the first time since the 1980's these birds are living in the wild.
"It's been nearly 40 years that we have seen a sihek fly free in the wild," Professor John Ewen, from conservation charity's Institute of Zoology, said.
He said the next big step was getting these native birds back to their native home on Guam
"What the sihek project represents is a hope spot for biodiversity protection."
Wegmann said it was crucial to support the long-term survival of more species.
"We are in the middle of an extinction crisis. Globally, we are seeing biodiversity losses around the world in in all types of ecosystems.
"And birds are one of the most heavily impacted groups of animals within this extinction crisis."