The Nature Of Birds

Many scientist maintain that birds descended from dinosaurs because fossils of dinosaur specimens with feather have been found. As a group, birds have exceptional eyesight - they have the largest eyes in relation to the size of their bodies. In addition, they have very light bones, which are suitable for flight. Just like their bills, birds' feet have also changed in accordance with the function and particular needs of each species. For instance, walking birds - like other vertebrate group - display a marked tendency towards having a reduced number of toes; ostriches, for example, have only two. Some birds of prey, such as eagles, have feet that are varitable hooks.

Skeleton and Musculature

Both lightweight and resistant, the skeleton of birds underwent important changes in order to adapt to flight. Some bones, like those of the skull and wings, fused to become lighter. Birds have fewer bones than vertebrates. Because their bones are hollow, containing internal air chambers, the total weight of their bones is less than that of their feather. Birds' spines tend to be very flexible in the cervical region and rigid neart the rib cage, where a large keel, to which the pectoral muscles attach. These large, strong muscles are used for flapping the wings. In contrast, running birds, such as ostriches, have more developed muscles on their legs.

Internal Organs

Birds in flight can consume oxygen at a rate that a well-trained athlete would not be able to withstand for even a fewer minutes. Because of this oxygen consumption, all their organs have had to adapt. The lungs of birds, though smaller than those of mammals of similar size, are much more efficient. Their lungs have several air sacks that both increase the efficiency of their respiratory systems and make them lighter. A special feature of the digestive system is a crop in the oesophagus, where food is stored for digestion or for feeding the young. A bird's heart can be four times larger in relation to its body size than a human's in relation to its body size.

The Senses

In birds, the senses organs are concentrated on the head, except for the sense of touch, which is found all over the body. Birds have the largest size with respect to the size of their bodies. This enable to see distant objects with considerable percision. Their field of vision is very broad, over 300 degrees, but in general they have little binocular vision. The ear - a simple orifice, but very refined in nocturnal hunters - helps them notice sounds in audible to humans, which facilatates the detection of prey while flying. The senses of touch and smell, on the other hand, are important only to some birds, and the sense of taste is almost nonexistent.

Feathers

Feathers are the feature that distinguishes birds from all other animals. They make birds strikingly colourful, protect them against cold and intense heat, enable them to move easily through the air and water and hide them from enemies Feathers are also one of the reasons why humans being have domesticated, caught and hunted birds. A bird's set of feathers is called its plumage, and its colour is essential for reproductive success.

Wings to Fly

Wings are highly modified arms that, through their unique structures and shape,enable most birds to fly. There are many types of wings; they vary by species. For instance, penguins, which are flightless. use their wings for the specialized task of swimming. Among all wings that have existed in the animal kingdom, those of birds are the best for flying. Their wings are light and durable, and in some cases their shape and effectiveness can be modified during flight. To understand the relationship between wings and a bird's weight, the concept of wing loading, which helps explain the type of flight for each species, is useful.

Type of Tail

Over the course of evolution, birds' tail vertebrate fused into a pegostyle, and in their place feather of different sizes and colours emerged. These feathers have multiple uses: they can control aerial manoeuvres during flight, works as brakes during landing and makes noise. Males also use them during courtship to dazzle and win over females. Usually, the tail is formed by rectrices that vary in number, length and rigidity depending on the species.

Gliding

Involves using air currents to fly and save energy when travelling long distances. There are two types of gliders, terrestrial birds and marine birds, each of which is adapted to different atmospheric phenomena. Terrestrial birds rise on the thermals (rising air currents). Marine Birds use oceanic surface winds. Once the birds gain altitude, they glide off in straight paths. They slowly lose altitude until encountering another thermal that will lift them. Both terrestrial and marine gliders have wings of considerable size.

Flapping Flight

Most flying birds use flapping flight all the time. It consist of moving through the air as if rowing with the wings. With each flap (raising and lowering), the wing both sustain the bird in the air and pushes its body forwards. There are different types of flapping flight and different rates of flapping, In general, the larger the bird, te more powerful and less frequent its flapping will be. Because flapping is an activity that consumes much energy, birds have adapted a variety of flight patterns: some, like hummingbirds, always flap their wings, whereas others alternate flapping with short-term gliding. The wing shape also varies according to the bird's needs. Birds that cover long distances have long, narrow wings; those that fly among trees have short, rounded wings.