London Zoo will stop the clock on its Victorian bird house today at noon to mark 100 years since the death of a passenger pigeon called Martha.
Martha was the last member of the species, which was once one of the most abundant birds in the world.
But passenger pigeons died out in a single generation, in one of the fastest and most dramatic extinctions ever seen.
Flocks of more than a hundred million of the birds were often seen in the sky in the 19th century, according to conservationists.
But passenger pigeon numbers fell dramatically within several decades, and they disappeared from the Earth altogether with the death of Martha at Cincinnati Zoo in the US in 1914.
A surge in hunting and deforestation is blamed for wiping the pigeons out.
At 12 noon today, the exact hour when Martha died, bird keepers will stop the clock on London Zoo’s clock tower outside of its bird house.
The zoo is dubbing today "Martha’s Day" in tribute.
Ken Norris, director of science at ZSL, said the 100th anniversary of Martha’s death would "draw attention to the plight of countless other species who continue to face extinction because of our actions.
“At ZSL we are working on dozens of conservation and research projects around the world to help prevent future extinctions, but as the example of the passenger pigeon demonstrates, we need to act as quickly as we can before there are many more Marthas.”
Mark Avery, a conservationist and former conservation director at the RSPB, has written a book on the pigeon's extinction, called 'A Message From Martha'.
"The passenger pigeon went from the most numerous bird on the planet to extinct in one human generation. That such a bird, such an economic resource, such a biological phenomenon, could disappear so rapidly teaches us that no species is safe - unless we act to conserve them."
The turtle dove could face a similar fate to Martha in the UK. It is the fastest-declining bird in the UK, with its numbers halving every six years, according to the RSPB. Turtle dove numbers in the UK are just 5% of what they were in 1970.
"It's too late for passenger pigeons, but 100 years on we don't have to accept that turtle doves will suffer the same fate," said Avery.
The Scottish wildcat, nicknamed the Highland tiger, could also become "extinct at any moment" according to wildlife experts.