This is a fruit bat (aka megabat, aka flying fox) automaton built out of LEGO by Jason Allemann of JK Brickworks. The engineering really is quite remarkable and it flaps its wings just like a real bat, not just up and down. Jason was inspired to build the model after a recent trip to Australia, presumably to celebrate not being killed by snakes or spiders.
Keep going for a video of the bat in action while Jason describes just what's going on.
Thanks to John K, who should build a kinetic sculpture of my aunt doing the funky chicken at my cousin's wedding.