Birds have a number of adaptations that enable them to fly. These adaptations include highly efficient digestive, respiratory, and circulatory systems; aerodynamic feathers and wings; strong, lightweight bones; and strong chest muscles. Most birds have these characteristics, even though some birds cannot fly.
Body Plan-they have a very active metabolism. They can eat, digest, and eliminate the waste in a short amount of time. Their body temperature is a rather high 102-103 degrees, they are endotherms. They have an extensive air sac system which reduces the weight of the bird and is used to dissipate the tremendous amount of heat build-up from metabolism. Their limbs are modified for various jobs based on the structure of their claws. They have hollow and strong bones; their forelimbs are modified as wings. These wings are homologues to the limbs of reptiles, amphibians, and mammals. Birds have 3 types of feather, down feathers, contour and quill.
Respiratory System- Birds have a unique and highly efficient way of taking in oxygen and eliminating carbon dioxide. When a bird inhales, most air first enters large posterior air sacs in the body cavity and bones. Observe the air sacs in the figure below. The inhaled air then flows through the lungs. Air travels through the lungs in a series of small tubes. These tubes are lined with specialized tissue, where gas exchange takes place. Due to high demand of air consumption for song and flight, birds have a unique and efficient breathing systems compared to other vertebrates. Birds have lungs supplement by air sacs to allow the ability to inhale more air than the lungs can hold. They fill all available species within an avian body cavity, helping decreases body weight for flight. The numbers of air sacs depends on the scarivy capacity of the birds. Diving birds have less air sac to reduce buoyancy as they submerge.
Circulatory System- Birds have four-chambered hearts and two separate circulatory loops. A bird's heart, unlike that of amphibians and most reptiles, has two separate ventricles, the right ventricle and the left ventricle. There is complete separation of oxygen-rich and oxygen-poor blood. One half of the heart receives oxygen-poor blood from the body and pumps this blood to the lungs. Oxygen-rich blood returns to the other side of the heart to be pumped to the rest of the body. This double-loop system ensures that oxygen collected by the lungs is distributed to the body tissue with maximum efficiency.
Excretory System- The excretory systems of many birds are similar to those of most living reptiles. Nitrogenous wastes are removed from the blood by the kidneys, converted to uric acid, and deposited in the cloaca. There, most of the water is reabsorbed, leaving uric acid crystals in a white, pasty form that you may recognize as bird droppings.
Digestive System- Birds' beaks, or bills, are adapted to the type of food they eat. Insect-eating birds have short, fine bills that can pick ants and other insects off leaves and branches, or can catch flying insects. Seed-eaters have short, thick bills. Carnivorous birds, such as eagles, shred their prey with strong hooked bills. Long, thin bills can be used for gathering nectar from flowers or probing soft mud for worms and shellfish. Large, long bills help birds to pick fruit from branches, while long, flat bills are used to grasp fish.Birds lack teeth, and therefore they cannot break down food by chewing it. However, many birds have specialized structures to help digest food. One such structure is the crop, which is located at the lower end of the esophagus. Food is stored and moistened in the crop before it moves further in the digestive tract.Birds lack teeth, and therefore they cannot break down food by chewing it. However, many birds have specialized structures to help digest food. One such structure is the crop, which is located at the lower end of the esophagus. Food is stored and moistened in the crop before it moves further in the digestive tract.
Nervous System- Birds have well-developed sense organs, which are adaptations that enable them to coordinate the movements required for flight. Birds also have a brain that can quickly interpret and respond to a lot of incoming signals. A bird's brain, shown in the figure below, is relatively large for its body size. The cerebrum, which controls such behaviors as flying, nest building, care of young, courtship, and mating, is quite large. The cerebellum is also well developed, as you might expect in an animal that uses precise, coordinated movements. The medulla oblongata coordinates basic body processes, such as the heartbeat.Birds have well-developed sense organs, which are adaptations that enable them to coordinate the movements required for flight. Birds also have a brain that can quickly interpret and respond to a lot of incoming signals. A bird's brain, shown in the figure below, is relatively large for its body size. The cerebrum, which controls such behaviors as flying, nest building, care of young, courtship, and mating, is quite large. The cerebellum is also well developed, as you might expect in an animal that uses precise, coordinated movements. The medulla oblongata coordinates basic body processes, such as the heartbeat.
Movement -Some birds cannot fly. Instead, they get around mainly by walking or running, like ostriches, or by swimming, like penguins. However, the vast majority of birds can fly. The skeletal and muscular systems of flying birds exhibit adaptations that enable flight. Although the bones in a bird's wings are homologous to the bones in the front limbs of other vertebrates, they have very different shapes and structures. In flying birds, many large bones, such as the collarbone, are fused together, making a bird's skeleton more rigid than a reptile's. These bones form a sturdy frame that anchors the muscles used for flight. The bones are strengthened by internal struts similar to those used in the framework of tall buildings and bridges. Air spaces make many bones lightweight. Birds also have large chest muscles that power the upward and downward wing strokes necessary for flight. The muscles attach to a long keel that runs down the front of an enlarged breastbone, or sternum.
Reproduction- Reproduction is internal in birds; the female has two ovaries, except in raptors, where it varies individually. Usually only the left ovary develops and like the male cloacal, shrinks after producing the season’s ova. Sperm is transferred to the female during copulation by direct contact of the two cloacae’s. The male briefly stands on the back of the female, the cloacae are pressed together (the “cloacal kiss”).
Behaviour-Bird brains are larger relative to body size than all other vertebrates except mammals.Many birds migrate long distances—often over hundreds of kilometers of open sea. Such migrations are usually seasonal.Feathers are made mostly of protein and develop from pits in the birds' skin. Feathers help birds fly and also keep them warm. The figure at right shows the two main types of feathers: contour feathers and down. Herons and some other birds that live on or in water also have powder down, which releases a fine powder that repels water.