Birdman - What does the ending mean? Can it be explained?

Link to the full episode of our movie podcast, with more discussion about the themes & symbolism of the film Birdman:
http://tinyurl.com/swg125

IMDB Info:
A washed up actor, who once played an iconic superhero, battles his ego and attempts to recover his family, his career and himself in the days leading up to the opening of a Broadway play.

Director: Alejandro González Iñárritu
Stars: Michael Keaton, Zach Galifianakis, Edward Norton, Emma Stone, Naomi Watts, Andrea Riseborough