the world > animals > birds > parts of or bird defined by > [noun] > head > part of (4)
The top of the head of a bird; = cap, n.1 10d.
Ornithology. The margin of the head, behind the bill, of birds, generally clothed with rigid bristles.
Ornithology. The pileum or top of a bird's head, especially when distinctively coloured. Cf. black cap, n. 2.
Ornithology. = pileum, n. Obsolete. rare.