A penguin. If all four walls face north the house must be at the southernmost point of the earth. Really, any native antarctic bird would work.
This brain teaser is quite similar to the guy whose house walls face south and sees a bear, then you’re asked the color of the bear. The bear would be white (a polar bear) as they’re the only bears indigenous to the north pole. A lawyer would claim it’s all circumstantial evidence and the bear could be an imported brown bear. The lawyer makes a valid point.