The sexes of the common pine chuck are so different in appearance that they look like different species.
The common pine chuck, Paraloxus larga, is a cardueline finch from the coniferous forests of Eurasia with great sexual dimorphism in which the male and the female look like two completely different species, from After Man: A Zoology of the Future. It is descended from the European greenfinch, which was a bird similar in physical appearance to the present-day female and the male has evolved his own distinctive features primarily for display and his eating habits are a secondary development.
Of the many seed-eating birds found in the coniferous forests, the largest by far is the common pine chuck. The two sexes of this species are quite different, both in appearance and in their mode of life. The male is much more powerfully built and is equipped with a massive beak, which he uses for breaking open pine cones to feed on the seeds. The female, much smaller and drabber, totally lacks the male's heavy beak and is really a scavenger supplementing her diet with carrion, grubs, adult insects, and other birds' eggs.
The male uses his heavy beak like a nutcracker to crush pinecones.