Just listened to your commentary for The Prestige again and want to extend on my earlier post.
Something I have just picked up on is the change in role for humans and animals in this movie through advancements in technology. At the start of the movie we have animals lives being sacrificed for the sake of the magicians performance. As time progresses throughout the movie we see Cutter develop the technology to the point where a bird trick can be performed without it being harmed.
In contrast, through the development of technology we see magicians going in the opposite direction. The new technology puts them (most specifically Angier) in a position where there lives are now the ones that are being sacrificed for the good of the trick.
I find it interesting how magicians and animals essentially swap roles by the end of the film.