Birds get their colors from various pigments and feather structures. One of those three pigments seen in birds is melanin.
Melanin occurs both in a bird’s feathers, but also their skin. Depending on the concentration of this pigment, different colors can be produced. From being more sparse, which can include colors such as reddish browns and light yellows, up to being more dense and producing dark blacks and browns. A benefit of this pigment is that it adds strength to feathers that contain this pigment, especially when this pigment is so concentrated.
This is why you see many birds, even those that are mostly white, with black wings, tails or just their primary feathers black. These feather groups are the most used and abused group of feathers on a birds’ body, necessary for flying, catching food, avoiding predators and just general survival.