Heartwarming moment when a researcher becomes foster mother to a flock of birds that became extinct in Europe in the last episode of Planet Earth III.
The latest episode of the BBC One documentary follows Katharina Huchler, in Austria, as she teaches the Northern Bald Ibis to migrate by flying with them over the Alps in a paraglider-like device.
Katharina had to trick the birds into thinking she was their parent because they didn't know where to migrate and had no example to follow.
Sir David Attenborough said during the program that it was 'very moving' to see a human being sensitive in a 'nature-loving way'.
In a clip from the episode, Attenborough said: 'Katharina Huchler is about to become a foster mother, and these are her new babies, 28 of one of the world's rarest birds, the Northern Bald Ibis.
'As the species flourished, the chicks followed their parents, but there are not enough of them to join them on their migration. You can't be raised without parents or someone who acts like parents do.”
Northern Bald Ibis are among the rarest birds in the world after being hunted to extinction in Europe more than 300 years ago, with the last remaining birds living mainly in Morocco.
As part of a daring plan to return them to their former habitat, Katharina sourced eggs from a zoo to raise the chicks herself.
She was with them all day, every day, feeding them and talking to them – a process called imprinting – so that the young birds would follow her everywhere.
Katharina said: 'They know they have to go somewhere, but they don't know in which direction and how far, so they have to learn the route from their parents.'
For the migratory birds to survive in the wild, they must fly south over the dangerous Austrian Alps to the warm feeding grounds of Italy in the fall.
Normally they would follow their natural mothers – but Katharina had to show them the way, using an ultralight aircraft to teach her young birds to fly to safety.
The BBC One documentary follows Katharina Huchler (pictured) in Austria, who raised a flock of Northern American Ibis chicks
Speaking on the programme, Sir David Attenborough said it was 'really very moving' to see how sensitive Katharina had been with the birds
Normally the birds would follow their natural mothers – but Katharina had to show them how to migrate, using an ultra-light craft
Since filming the series, another 60 birds have successfully learned to migrate
Attenborough added: 'The sequence of the researchers calling the birds and then leading them along the mountain range is one of the most moving, but not even moving, optimistic sequences I can think of.
'People behave in a disinterested, caring and loving way towards the natural world. When I see that happening, to dedicate your life, I find it very moving.'
Katharina said: 'What we're trying to do, besides saving the ibis, is trying to give people hope. If we can bring back one species, we can do the same with others.'
Producer-director Steve Greenwood says: 'This was the most extraordinary conservation story I've ever come across, so I just had to have it in the hero film.
'It's both inspiring and amazing. Filming it was a huge challenge because the birds could never see or hear the director and film crew.
'When the young birds were in the container or the aviary, we were hidden in a shelter, with only the camera lens sticking out. Questions were written down and sent to the foster mothers via our mobile phones.'
The final episode of Planet Earth III airs this Sunday at 6.20pm on BBC One and iPlayer.