You may have heard that BBC will be
providing videos on Youtube. Well in one such clip added by BBC Worldwide (Feb 2007) - Here David Attenborough imitates the double-tap sound of a Magellanic Woodpecker (
Campephilus magellanicus) in the Patagonian forests of South America. Watch as he makes a double-knock sound on a resonant tree-trunk. The camera scans the quiet forest, and a reply is heard! The bird approaches to investigate its rival as David watches in fascination.

Magellanic Woodpeckers by Arthur Grosset, Chile, 2005. Courtesy of Mangoverde World Bird Guide.
Woodpeckers are able to cling certically to tree trunks and can drill holes into wood. Their chisel-shaped beaks and a "suspension system" in their skulls allow them to peck with great force but prevents them from getting soft in the head!
Links of interest:
You can hear the drilling sound of the woodpecker even in Singapore. Here is a photo from Sungei Buloh Wetlands Reserve that I took in August last year. That familiar sound announced its presence, as it searched for insects on a mangrove tree nearby.
