Clinodactyly
Clinodactyly is a medical term describing the curvature of a digit (a finger or toe) in the plane of the palm, most commonly the fifth finger (the "little finger") towards the adjacent fourth finger (the "ring finger"). It is a fairly common isolated anomaly which often goes unnoticed, but also occurs in combination with other abnormalities in certain genetic syndromes, such as Down syndrome, Turner syndrome and Cornelia de Lange syndrome. In birds
Anisodactyly
Anisodactyly is the most common arrangement of digits in birds, with three toes forward and one back. This is common in songbirds  and other perching birds, as well as hunting birds like eagles, hawks, and falcons. This arrangement of digits help with perching and/or climbing and clinging. This occurs in Passeriformes, Columbiformes, Falconiformes, Accipitriformes, Galliformes and a vast majority of other birds. Syndactyly
Syndactyly, as it occurs in birds, is like anisodactyly, except that the third and fourth toes (the outer and middle forward-pointing toes), or three toes, are fused together, as in the belted kingfisher (Megaceryle alcyon). This is characteristic of Coraciiformes (kingfishers, bee-eaters, rollers, and relatives). Zygodactyly
Zygodactyly (from Greek ζυγος, even-numbered) is an arrangement of digits in birds and chameleons, with two toes facing forward (digits 2 and 3) and two back (digits 1 and 4). This arrangement is most common in arboreal species, particularly those that climb tree trunks or clamber through foliage. Zygodactyly occurs in the parrots, woodpeckers (including flickers), cuckoos (including roadrunners), and some owls.
Zygodactyl tracks have been found dating to 120–110 million years ago (early Cretaceous), 50 million years before the first identified zygodactyl fossils. All Psittaciformes, Cuculiformes, the majority of Piciformes and the osprey are zygodactyl. Heterodactyly
Heterodactyly is like zygodactyly, except that digits 3 and 4 point forward and digits 1 and 2 point back. This is found only in trogons, though the enantiornithean Dalingheornis might also have had this arrangement. Pamprodactyly
Pamprodactyly is an arrangement in which all four toes point forward, outer toes (toe 1 and sometimes 4) often if not regularly reversible. It is a characteristic of swifts (Apodidae) and mousebirds (Coliiformes). Chameleons
The feet of chameleons are organized into bundles of a group of two and a group of three digits which oppose one another to grasp branches in a pincer-like arrangement. This condition has been called zygodactyly or didactyly, but the specific arrangement in chameleons does not fit either definition. The feet of the front limbs in chameleons, for instance, are organized into a medial bundle of digits 1, 2 and 3, and a lateral bundle of digits 4 and 5, while the feet of the hind limbs are organized into a medial bundle of digits 1 and 2, and a lateral bundle of digits 3, 4 and 5. On the other hand, zygodactyly involves digits 1 and 4 opposing digits 2 and 3, which is an arrangement that chameleons do not exhibit in either front or hind limbs.