The stresses involved
in landing and taking off, in running and in hunting mean that a variety
of birds have relatively heavy and strong leg bones. Large raptors such
as Eagles kill their prey with their feet and carry the prey considerable
distances. When you look at a skeleton of an Eagle it is surprising
how large the legs are. Ratites (Ostriches, Rheas and Emus) are large
birds which run, rather then fly to escape predators, this means that
they have been able to develop large heavy leg bones. The fundamental
bones of a bird's leg are the femur, fibula, tibiotarsuss and tarsometatarsus.
These are also called the femur, tibia and tarsus respectively in an
external view of a bird's anatomy. Most birds have four toes. The first
points backwards in most species and consists of a small metatarsal
and one phalanx (toe bone). The second, third and fourth digits or toes
are counted from the inside of the foot out and have 2, 3 and 4 phalanges
respectively. The fifth toe is lost
Here are some pictures
of bird's feet to demonstrate what was said above and below.
The size and shape of the claws and the way the toes are arranged as well as the length of the toes and the degree of webbing are all dependent on what a bird uses its feet for and where it lives. Like a bird's bill or beak its feet reveal a lot about its lifestyle. Many birds have three toes forwards and one back, others have two forward and two back.
Ducks, Geese and Swans all have medium length toes joined together by a web of skin to make an excellent paddle for rowing themselves through the water. They spread the toes on the back stroke to maximize the push then hold their toes together on the forward stroke in order to reduce resistance. Jacanas have extra long toes to help spread out their weight as they trot across the Lilly pads. Swifts have two toes that can be facing forward or backwards / opposed to the first two as needed.
Information on this page was contributed by EarthLife.
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