Brown-rumped, edible-nest swiftlets nesting at 500 feet up a sheer wall of the Gomanton caves in Sabah, Borneo. The nests, woven purely from the birds' saliva, adhere to the surface of the rock, enabling the birds to inhabit locations which are difficilut for predators to reach - but not impossible for man! The nests are highly regarded in Chinese cuisine, although almost tasteless, and can be cooked in several ways, but most typically as bird's nest soup..