Would it be possible to morph from a compositon of ducks in the M shape to the form of the letter M? I read about the reshape filter, but that is referring to more of a person to animal/things with the same shape & dimensions. Can you tween between various objects like some of the older Adobe programs?
The common approach is to explode a particle system that uses a layer's Alpha as the emitter shape and then pre-compose and time-reverse it. With vanilla AE this can be done with Particle Playground, Card Dance or Foam, all of which use specific layer maps to modulate motion. Depending on which method you employ, you'd assign your animals as the custom particle and then animate your map to mimic gravity and other forces.... If you have Trapcode Particular, then this would be similar, but this plug-in has internal forces which would avoid having to create those maps. If you do a generic web search for "text to sand" or "birds assemble logo", you will no doubt find several forum posts and a few tutorials on teh matter. The specific details will depend on what look you are after and what tools are at hand...