Very nice brendon, I think this photograph really captures the nature of the owl quite well. Do you have a frame of it looking directly at the lens. They have such wonderful eyes, its a shame not to capture that direct stare.
Through a glass, huh? That's hard to do without getting all kinds of glare at such close range (especially when using a flash), even with a polarizer, which you didn't mention using, so I assume you didn't...great shot. Though, had you left out the part about it being in captivity, I'd've been in awe...getting an owl in its nest in the wild is a rather difficult thing to do, ESPECIALLY at close range. :) I agree with Ray. Would've been nice to see this in color, though. Owls have BRILLIANTLY colored eyes. But it works well in black and white. Good job. :)
When I first saw this was shot with only a 50mm lens, I was amazed - then saw your note that it was shot through a glass cage :-) Even so, you captured it well, with a slight catchlight in the eyes and a good lighting balance to show detail but still give the impression of a night shot. Well done.