The naturalist on the battle of filming the birds of Borneo, whose nests made of saliva are prized by Chinese chefs. From 2009.
Filming the birds that make the nests of saliva so prized by Chinese gourmet chefs in the total darkness of a Borneo cave proved difficult, until a conical mound of bat guano provided a natural platform.
Series of talks by Sir David Attenborough on the natural histories of creatures and plants from around the world.
First broadcast on BBC Radio 4 in September 2009.