NEW YORK, Dec. 10 (Xinhua) -- The world's oldest known wild bird, a female Laysan albatross which is at least 68 years old, has laid another egg in a U.S. refuge after raising more than 30 other youngsters, according to the U.S. Fish and Wildlife Service (USFWS).
"She first appeared back at her traditional nest site on November 29 and biologists on Midway have confirmed that she has laid an egg," the USFWS Pacific Region said in a statement, referring to the Midway Atoll National Wildlife Refuge on the Hawaiian archipelago.
The albatross, called Wisdom, was believed to have hatched around 1951 in the refuge. In 1956, she was first banded as an adult by an ornithologist named Chandler Robbins for study, but then returned to the wild. Robbins, who passed away last year, "rediscovered" Wisdom 46 years later during a survey near the same nesting location.
Wisdom and her mate Akeakamai have met on Midway to lay and hatch an egg every year since 2006. It has been observed that albatrosses mate for life and an albatross would only seek another mate when its original mate had died.
Wisdom is believed to have reared between 30 and 36 chicks so far in her life. It takes somewhat over two months for albatross parents to incubate an egg and another five months before a chick leaves the nest, during which period they will take turns incubating the egg or caring for the chick while the other forages for food at sea, biologists said.
Albatrosses are known for their fidelity to nest sites. In 2017, the chick Wisdom fledged in 2001 was observed close to her current nest, the USFWS said.
"Midway Atoll's habitat doesn't just contain millions of birds, it contains countless generations and families of albatrosses," said Kelly Goodale, a USFWS biologist at the refuge.
"If you can imagine when Wisdom returns home she is likely surrounded by what were once her chicks and potentially their chicks. What a family reunion!" Goodale added.
The Midway Atoll National Wildlife Refuge, managed by the USFWS and also a memorial site of the Battle of Midway in World War II, claims nearly 70 percent of the world's Laysan albatross population, according to the USFWS statement.