91Èȱ¬

The world's oldest known bird, a Laysan albatross named Wisdom, has hatched a chick at the age of 70.

It's pushed scientists to question their understanding of birds - because lots of them thought she wouldn't live for this long.

Wisdom turned 70 this year and it's thought that this chick will be her 40th.

The chick was hatched last month on Midway Atoll, a small scrap of land 1,300 miles north west of Hawaii that forms part of a wildlife reserve. Wisdom returned last month with her mate to hatch the chick.

US Fish and Wildlife biologist Beth Flint said: "Each year that Wisdom returns, we learn more about how long seabirds can live and raise chicks".

Wisdom was first banded by Chandler Robbins, a biologist working at Midway Atoll, back in 1956 - banding is a small item placed on the bird's leg, so when they are spotted by researchers and biologists they can track and record the bird's movements and wellbeing.

It was initially thought that Laysan Albatross birds had a life span of 40 years, but Wisdom is now teaching researchers more about the species.

In 2002, Chandler Robbins had noticed a bird with a ragged band that needed replacing and was shocked to discover it was the same bird he had banded back in 1956 - that's right, Wisdom!

Wisdom continued to show up at Midway Atoll and hatching chicks - it's estimated that this new chick she hatched last month will be her 40th.

Beth Flint from the US Fish and Wildlife Service said: "Her return not only inspires bird lovers everywhere but helps us better understand how we can protect these graceful seabirds and the habitat they need to survive into the future."

Wisdom has been raising chicks with her current mate Akeakami since 2010. The birds usually have one mate for life, but due to her outstanding age she has outlived her previous mates.

Laysan albatross birds usually only hatch one chick at a time, and they do not lay eggs each year - this means that each chick is a valuable one and their survival into adulthood makes a difference in population numbers.

She has impressed biologists because there are so many factors that she must fight against to survive, such as storms and tsunamis, becoming prey for sharks and now the impact of plastic pollution.