Wow.....that looks like a nice job of building. Whoever did that did a good job.
As Mary suggests..........what about the ventilation?
What would be ideal is if a design like that could be reversed, with the openings to the high side and the high side facing south to the winter sun. Windows and open vents to the south. Winter is coming and when it gets here having windows and openings to the south will make a lot more sense.
I am always amused by the ramps. The birds can easily fly up to the opening, so what they really need is a platform outside the pop door to land on / fly up to. No ramp like that is ever needed, but is traditional and cute a lot of folks include them. Again......no harm done, but still amusing.......at least to me. But I'm an old grumpy curmudgeon and "cute" isn't in my lexicon.