The anatomy of bird legs and feet varies, including many accommodations to perform various functions.
Most birds are classified as digitigrade animals, meaning they walk on their feet, rather than entire legs. Some of the underlying bones (distal and mostly metatarsal) fuse to form tarsometatarsus - the third segment of the limbs, especially for birds. The leg bone (proximals), in turn, merges with the tibia to form the tibiotarsus, as the centrality of time passes away. The fibula is also reduced.
The legs attach to a strong assembly consisting of a broadly embedded pelvis with a uniform spinal bone (also specifically for birds) called synsacrum, which is constructed from several unified bones.
Video Bird feet and legs
Skeleton
Hindlimbs
Birds are generally digitigrade animals (pedestrians), which affect their skeletal structure. They only use their hind legs to walk (bipedalism). Their forelimbs evolved into wings. Most bird leg bones (excluding toes) fuse together or with other bones, after changing their function from time to time.
Tarsometatarsus
Some of the lower leg bones together to form tarsometatarsus - the third segment of the foot that is specific to birds. It consists of the distal and metatarsal combinations II, III and IV. Metatarsus I remain separated as the base of the first toe. The tarsometatarsus is an extended leg area, which gives the legs an extra long lever.
Tibiotarsus
The upper leg bone (proximal) integrates with the tibia to form the tibiotarsus, whereas centralia is absent. The front side (front) of the dorsal end of the tibiotarsus (on the knee) contains prominent enlargement called the cnial emblem.
Patella
On the knee above the cnemial peak is the patella (kneecap). Some species do not have a patella, sometimes only a small extension of the cnial emblem. In grebes both the normal patella and the extension of the cnial emblem are found.
Fibula
The fibula is reduced and adheres extensively to the tibia, usually reaching two-thirds of its length. Only penguins have long full fibula.
Knees and ankles - confusion
The bird's knee joint between the femur and tibia (or rather the tibiotarsus) points forward, but is hidden inside the feathers. The visible "ankle" (ankle) is a connection between the tibiotarsus and tarsometatarsus. The joints in the tarsus occur also in some reptiles. It should be noted here that the name "thick knees" of Burhinidae family members is a misnomer because their heels are large.
The chicks in the order Coraciiformes and Piciformes have ankles covered by a hard patch of skin with tubercles known as heel-pad. They use a heel-pad to shuffle in a hole or hole.
Unused toes and metatarsal
Most birds have four toes, usually three facing forward and one pointing backwards. In typical perch birds, they each consist of 3, 4, 5 and 2 phalanges. Some birds, like sanderling, have only the toes facing forward; this is referred to as tridactyl foot. Others, like ostriches, have only two toes (doactic feet). The first digit, called hallux, is homologous with the human toe.
These claws are located in the extreme phalanx of each toe. They consist of keratinous podotheca, or sheath, and are not part of the skeleton.
The bird's legs also contain one or two metatarsals that do not coalesce in tarsometatarsus.
Pelvic corset and synsacrum
The legs are attached to very strong and lightweight assemblies consisting of a widely fused pelvic girdle with a uniform spinal bone called synsacrum, which is specific to birds. Synsacrum is built from lumbar fused with sacral, the first few parts of caudal, and sometimes one or two last sections of the thoracic vertebra, depending on the species (the bird has the whole between 10 and 22 vertebrae). Except for ostriches and rheas, pubic bones are not connected to each other, making it easy to lay eggs.
Stiffness and mass reduction
The fusion of individual bones into a strong and rigid structure is characteristic.
Most bird bones are widely pneumatized. They contain many air pockets connected to the air sacs of the lung from the respiratory system. The chewy interior makes them strong against their masses. The number of pneumatic bones depends on the species; little or no pneumaticity in birds that dive. For example, in long-tailed ducks, leg bones and wings are not pneumatic, unlike some other bones, while loons and puffins have a more massive, boneless skeleton that is aired. Ostriches and emus that can not fly have pneumatic femurs, and so far only pneumatic bones are known to these birds except the cervical cervical vertebrae.
Fusion (leading to stiffness) and pneumatic bone (causing reduced mass) are some of the many birds adaptations to fly.
Plantigrade mill
Most birds, except loon and grebes, are digitigrade, not plantigrade. Also, the chickens in the nest can use the entire foot (toes and tarsometatarsus) with heels on the ground.
Loons tend to run in this way because their feet and pelvis are very special for swimming. They have a narrow pelvis, which moves the attachment point of the femur to the back, and their tibiotarsus is much longer than the femur. It shifts the foot (toes) behind the center of the loons body mass. They walk usually by pushing themselves on their chests; bigger birds can not take off from the mainland. This position, however, is perfect for swimming because their legs are behind like propellers on a motorboat.
Grebes and many other waterfowls have shorter thighs and shorter or narrower pelvis, which gives the impression that their feet are attached to the back like a burrow.
Maps Bird feet and legs
Function
Since the forelegs of birds are wings, many of the forelimb functions are performed by bills and hind legs. It has been proposed that hindlimb is important in aviation as an accelerator at take-off. Some leg and foot functions, including those that are conventional and those specific to birds, are:
- Locomotion
- Walk, run (ostrich, grouse, wild turkey) jump, climb (woodpecker, nuthatches, treecreepers)
- Swim and drive under water (ducks, grebes, loons)
- Perched (as in a branch) or pasted
- Takes (like ospreys holding a fish)
- Associated with flights
- Serving may be the main take-off accelerator. In a common vampire bat, on the contrary, the force required is produced by the wings.
- Absorbs a surprise landing on a perch and above water, into a "water ski"
- Feed and connect
- Capture and kill prey in raptors (eagles, owls)
- Holding (used like a hand in a parrot) and separating food (with help from billing)
- Scratching the ground for food
- Double strokes: jump forward and backward with both feet to scratch (often towhees, sparrows, juncos)
- One foot stroke (grouse, quail, wild turkey, chicken)
- Reproduction and related
- Holding and rolling eggs during incubation. Birds that do not have ponds contemplate hatching eggs with their feet - grasping one or even two of them (gannet, boobies) or keeping them on the top surface of their feet (penguins under the abdominal skin pouch, murres).
- Dating (wise grouse), including air dating (bald eagle)
- Build a hive (with help from billing)
- Cleaning and cleaning. Sometimes birds use special claws (for example, the owl barn has what is called a "feather combs"). Some herons and nightjars use claws to clean their heads.
- Setting heat loss (heron, gulls, giant petrel, heron, New World vultures, ducks, geese)
Foot Settings
Typical settings in birds are:
- Anisodactyl : three toes in front (2, 3, 4), and one behind (1); in almost all the singers and other birds of the perch.
- Zygodactyl : two toes in front (2, 3) and two on the back (1, 4) - outer toes (4) are reversed. The zygodactyl arrangement is a case of convergence, since it evolved in birds in different ways nine times.
- In many birds perched - mostly woodpeckers and their allies, ospreys, owls, cuckoo birds, parrots, mousebirds, some swifts and cuckoo rolls.
- The woodpecker, while climbing, can rotate the outer rear digit (4) to the side in an ektropodactyl arrangement. A black woodpecker, a three-fingered woodpecker of Eurasia, and a three-footed three-fingered American juggler have three toes - the back of the back (1) is missing and the rear exterior 4 always points back and never rotates.
- Owls, osprey and turacos can rotate the outer toes (4) back and forth.
- In many birds perched - mostly woodpeckers and their allies, ospreys, owls, cuckoo birds, parrots, mousebirds, some swifts and cuckoo rolls.
- Heterodactyl : two front fingers (3, 4) and two fingers on the back (2, 1) - the inner toes (2) are reversed; the outer heterodactyl arrangement exists only in trogons.
- Syndactyl : three toes in front (2, 3, 4), one behind (1); the outside and the middle (2, 3) join for a portion of its length. Regular in Coraciiformes, including kingfishers and hornbills.
- Pamprodactyl : the two inner toes in front (2, 3), the outer two (1, 4) can spin freely forward and backward. In the mousebirds and some swifts. Some swifts move the four digits forward to use it as a hook to hang.
The most common setting is anisodactyl foot, and second among perching birds is the zygodactyl setting.
Webbing and lobes
Palmations and lobes allow swimming or help walking on loose soil like mud. Webbed or webbed feet can be categorized into several types:
- Palmate : only the anterior digits (2-4) are joined by webbing. Found in ducks, geese and geese, seagulls and terns, and other aquatic birds (auks, flamingos, fulmars, jaegers, loons, petrels, shearwaters and skimmers). Duck divers also has curved hind legs (1), and seagulls, terns and allies have reduced back toes.
- Totipalmate : all four digits (1-4) join webbing. Found in gannets and boobies, pelicans, cormorants, anhinga and frigatebirds. Some gannets have brightly colored legs used on the screen.
- Semipalmate : a small net between the anterior digits (2-4). Found in several plovers (Eurasian dotterels) and sandpipers (semipalmated sandpipers, stage sandpipers, highland sandpipers, bigger yellowlegs and willet), avocet, heron (just two toes), all grouse, and some breeds of domesticated poultry. Plovers and lapwings have vestigial rear legs (1), and sandpipers and their allies have reduced back toes and are lifted barely touching the ground. Sanderling is the only sandpiper that has 3 toes (tridactyl foot).
- Lobate : the anterior digit (2-4) edges with the skin lobe. Lobes expands or contracts when a bird swims. In grebes, coots, phalaropes, finfoots and some ducks legs in hallux (1). Grebes has more webbing between toes than coots and phalaropes.
The palmate legs are the most common.
Thermal settings
Some birds such as seagulls, buds, ducks or swans can regulate their temperature through their legs.
Arteries and veins are interwoven in the legs, so heat can be transferred from the arteries back into the vein before it reaches the foot. Such a mechanism is called a counter-exchange. Seagulls can open the shunts between these vessels, reverse the flow of blood above the feet, and constrict the vessels in the legs. This reduces heat loss by more than 90 percent. In seagulls, the base temperature of the foot is 32 ° C (89 ° F), while the foot may be close to 0 ° C (32 ° F).
However, for cooling, these heat exchange networks can be bypassed and blood flow through the legs increases significantly (petrel giant). Some birds, also eject their feet, increase heat loss through evaporation (storks, New World vultures).
See also
- Bird Anatomy
- Dactyly
- Synsacrum
- Tarsometatarsus
- Tibiotarsus
References
Source of the article : Wikipedia
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