During cruise the pilot stated that the aircraft had experienced stronger than expected headwinds so he allowed the left fuel tank to run dry in order to maximise endurance before changing to the right tank, the contents gauge of which indicated about 6 US gallons remaining. A few minutes later the engine failed, and although the pilot performed all the necessary emergency procedures he was unable to restore power. He made "Mayday" transmissions on the Area and CTAF frequencies, then looked for a clear area to carry out a forced landing. There being no suitable areas within gliding range he was committed to stalling the aircraft into the tree tops. The emergency locator beacon activated. An investigation of the aircraft revealed there was no fuel in the left tank, and as the right tank had suffered damage at impact it was not possible to determine if there had been fuel in it prior to the accident. Fuel stains were noted behind both tank filler caps, indicating that some fuel syphoning may have occurred in flight.