NEW YORK (CBSNewYork) — Three rare maleo chicks have been hatched at the Bronx Zoo.

The birds are native to Indonesia and the Bronx Zoo is the only other place in the world to see the endangered birds, the Wildlife Conservation Society said in a press release.

The zoo studied and recreated the specialized conditions needed to successfully incubate the birds’ eggs.

In the wild, female maleos usually lay and bury their eggs in underground nests that are heated by geothermal sources or the sun. So, the zoo put sand in their nesting areas and heated it electrically from below. Once an egg is laid, it is dug out and moved to an incubation room.

The incubation period for a maleo is unusually long, meaning the chicks hatch at a relatively mature stage and are able to dig themselves up through three feet of earth. They can also fly and forage and need no parental care after hatching.

Each of the chicks at the zoo hatched after about 70 days of incubation.

The chicks are healthy and are currently not on exhibit at the zoo, the WCS said.

In total, the zoo has nine maleos.

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