Red-billed Quelea

During breeding the male is distinguished by its more colorful plumage and red bill. Breeding plumage in male queleas is unusually variable: comprising a facial mask which ranges from black to white in color, and breast and crown plumage which varies from yellowish to bright red. For the rest of the year male plumage resembles that of the female, which is a cryptic beige coloration. The female's bill is yellow during breeding, and red during the non-breeding season. (wikipedia)