Beaks, heads, and tails of birds.
Note the large differences between beaks, based on the food type of the bird.
I’ve always found the parrot beak very interesting - though they subsist almost exclusively on nutmeats, they have a beak structure very similar to that of the raptors and other birds of prey. Their tongue, however, is much more tactile and dextrous. Many nuts and seeds are encased in shells or pulps that are poisonous to the birds, so they have to be able to expertly remove every part of the poison before eating.
Zoological Science or Nature in Living Forms. A. M. Redfield, 1858.