"It is a window."
There's no direct object Corbin. Direct object is something that the verb acts upon or the action (of the verb) is performed on the direct object. I eat cake - I is the subject, cake is the object - ie. It's what I'm eating. The dog bites me - the dog is the subject, me is the object - ie. I'm what the dog bites. The girl throws the ball - the girl is the subject, the ball is the object - ie. what the girl is throwing. The verb to be doesn't take a direct object - it doesn't carry out an action on an object. Usually it's like an equals sign - A is B - The water is cold, I am C - I am tall, you are D - you are kind.
When it comes to 'person' ie. 1st person singular, 2nd person singular, 3rd person singular etc that is included in the verb. In this instance it is easy to conclude that the 'person' included in the verb here is 'it' (3rd person singular) as the window is a thing, an object and therefore not a he or a she. So まど - a window, です - it is - It is a window.
Well... これ would imply that it is next to you, that's not the issue with our feathered friend. However, at least I wouldn't point out an object next to me and say "it", but rather "this". When you say "これ", it implies more of a "this" instead of "it". それ is a bit more loose with either meaning "it" or "over there" or "that's" or (any of the endless varients), but これ is much more rigid in meaning "this"...