What is the difference between flying birds and waterfowl?

First, to fly, you must have a light body. Therefore, all flying birds have light bones and for the most part they are not very large. Also, the plumage of flying birds reduces air resistance. There is also a tail, which plays the role of a rudder during flight, and helps to brake when landing. Waterfowl have other features of the body structure, for example, a thick layer of fluff and subcutaneous fat, which saves from rapid loss of heat in water, etc.