Like a warm sweater, the worst thing about down is how absorbent it is. Down quickly gets soaked and mats together when wet. So not only do loons have to keep their skin dry, but also keep all of their down feathers dry. They can do this thanks to their outer contour feathers. These feathers cover every millimeter of down and skin, working like a perfect rain suit, or a diver's dry suit.
Contour feathers take their name from the fact that they give loon bodies their shape, or contour.
Loon contour feathers are beautifully patterned black and white. The white parts of the neck feathers are longer than the black, giving a loon's neck the texture of exquisite velvet corduroy. Contour feathers are designed to keep the body inside nice and dry. Water molecules are attracted to other water molecules, and that's why water forms droplets rather than sheeting away on most surfaces. Contour feathers are so tightly fitted together that drops of water can't squeeze between.