The bird's foot or barrel exhibits a number of morphological differences from the foot of other terrestrial vertebrates . The number of toes varies between two and four, depending on the species, the latter being the rule. The bird's foot is mostly featherless and covered with horn scales. Claws are formed at the end of the toes .
With birds of prey , both feet are also referred to as "catches" (individual catch ), as they are used to grab and hit the prey.
In birds, the ankle joint (tarsal joint) is developed differently than in mammals, since the bones of the original proximal row of bones of the ankle joint grow together with the shin to the tibiotarsus and those of the distal row with the metatarsal bones to the tarsometatarsus ( running leg ). Instead of a composite tarsal joint, a simple bone connection known as an intertarsal joint is thus formed.
The metatarsus or "run" in the narrower sense is supported by the metatarsal bone already mentioned. In birds, regardless of the number of toes, only one leg is formed. This has a bony bulge on the back, the "hypotarsus", with grooves or channels for the tendons of the toe flexor muscles.
The number of toes in birds varies between two and four, depending on the species . Most birds have four, only one species, the African ostrich , has only two. The number of phalanges (phalanges) is one unit larger than the ordinal number of the respective toe; the first toe has two links, the second three, the third four, and the fourth five.
According to the number of toes and their arrangement on the foot, a distinction is made between different types of bird's foot.
- The anisodactyl toe arrangement is the most common and can be found, for example, in all songbirds . The first toe points backwards and the other three forwards.
- The zygodactyle arrangement is the second most common form: the first and fourth toes point backwards, the second and third forwards. Zygodactyly is typical for parrots , owls and the cuckoo , for example .
- The heterodactyl arrangement corresponds to the zygodactyl, but here toe 2 instead of toe 4 is directed backwards. In this shape, the first and second toes point backwards, the third and fourth forwards. Such an arrangement can only be found in the trogons .
- In the pamprodactyl arrangement, all four toes point forward. The first and fourth toes can move freely forwards and backwards. Most sailors have this toe position and can hold on to vertical structures.
- In syndactyly , the second and third toes have partially grown together. This is found in the kingfishers and other representatives of the rockfish .
- If the first toe is completely missing, this is known as tridactyly . A Dreizehigkeit occurs in many ratites ( emus , rheas , cassowaries ), bustards and many Regenpfeiferartigen on.
- The two-toedness of the bouquet is called didactyly .
The bird's foot is mostly featherless and covered with horn scales. The last phalanx usually has a pointed horn cover in the form of a claw . In waterfowl, skin folds in the form of webbed feet are formed between the toes .
- Franz-Viktor Salomon, Maria-Elisabeth Krautwald-Junghanns: Anatomy of the birds. In: FV. Salomon et al. (Ed.): Anatomy for veterinary medicine . 2nd ext. Edition. Enke, Stuttgart 2008, ISBN 978-3-8304-1075-1 , pp. 754-814.
- life.uiuc.edu: External anatomy of birds (English, PDF file; 1.19 MB)