OK, so I was watching the DVD of the Jacques Perrin/Jacques Cluzaud documentary Travelling Birds (Le Peuple Migrateur) last night, and what should I see at about 8 minutes in, but the following sequence:
~Migratory ducks arrive in snowy landscape.
~Ducks settle down to weather out the cold and blustery night.
~Ducks awake in the morning. The blizzard has subsided.
~Ducks make many and sundry quacking noises.
~An avalanche begins and ducks fly away.
There you have it: a filmic record of a duck's quack starting an avalanche! (Sure, the film-makers try and make it look like the avalanche startles the ducks and causes them to take flight, but I believe the footage speaks for itself. Go rent the DVD. Tell me I'm wrong.)
In further news, this site reveals that scientists at Sanford University have carried out a comprehensive Duck Quack and Echo experiment, so those nitpickers who scoffed at my own exposé (no names except to say Universal Head) can now go view a (sniff) proper experiment.