I am no birder as you will soon know.
The other morning, lying in bed, a gang of feathered friends lurking outside my window were very distinctly sing-songing in their best helium-inspired voices..."Your cat is silly. Your cat is silly. Your cat is silly..."
Uninformed question (formerly known as "Stupid Question"

) for you. How can you see them at night well enough to differentiate one type from another? Or do you do that largely by sound?