What is the main characteristic of birds known as raptors?

The scissor-tailed flycatcher, Tyrannus forficatus, is the Oklahoma State Bird.

Class characteristics:

• Body covered with feathers
• Bones of the skeleton are thin, with air spaces
• Forelimbs function as wings, not for grasping
• Toothless beak
• Body temperature is internally regulated
• Heart is 4-chambered

The wild turkey, Meleagris gallopavo, is the state game bird.

Birds are special they are the only vertebrates with the ability to fly. In addition to aerodynamics, birds must have a high surface-area-to-weight ratio and lots of power to fly. There are many body adaptations that allow them to do this.

Flight adaptations:

• Flight muscles - The massive pectoralis brings the wing down in its power stroke. The supracoracoideus lifts the wing. These two muscles make up almost 35% of the total body weight, providing lots of power.

• Feathers Birds have an enormous number of feathers. Although they are light-weight, they may weight up to twice as much as the bird's skeleton.

• Bones Many of the skeletal bones are not solid. They are hollow but reinforced internally with trusses similar to those used in airplane wings. The breast bone is very broad to anchor the pectoralis muscle. Rigidity of the skeleton is obtained through the fusion of bones, the middle to lower vertebrae in particular. All birds, even small ones, have a large number of cervical vertebrae (13 to 25). These saddle-shaped vertebrae permit great flexibility, allowing the bird to reach all parts of its body with the bill for preening feathers.

• Organ reduction - No birds have teeth. The hand and foot have only 3 fingers and toes, each with only 1 or 2 phalanges. The fibula is degenerate and the caudal vertebrae have decreased in number. There is no urinary bladder, no external sex organs, and usually only one ovary.

• Wings - Primary flight feathers are found on the fingers bones of birds. The secondary flight feathers are found on the forearm. When birds are flying, movement of the hand with its large primaries forms a figure eight or oval in the air, the primary feathers providing the surface area for most of the propulsion. The forearm moves little by comparison, but its secondaries control the shape of the wing providing most of the lift.

• Metabolism - Birds have a very high rate of metabolism to produce the energy needed for flight. Herbivorous species can digest berries and defecate waste from them in 15 to 30 minutes. Meat eaters can digest small mammals in 3 to 4 hours. This high metabolic rate maintains a high body temperature. Body temperatures in birds range from 38^oC to 44^oC, compared to mammals which range from 36^oC to 39^oC.

• Circulation - The circulatory system of birds is very efficient. Their heart is 1 1/2 to 2 times larger than that of a equal-sized mammals. Smaller, highly active birds have proportionately larger and more rapidly beating hearts than those of larger birds. The heart rate ranges from 1000 beats per minute in a hummingbird to about 400 beats per minute in a domestic chicken.

• Respiration - The respiratory system of birds makes up nearly 20% of the volume of the body, compared to less than 10% in mammals. Birds remove about 31% of the oxygen from inhaled air, while mammals remove only about 24%. The lungs of birds are molded to the ribs. Since there is no diaphragm, aeration of the lungs is accomplished by rib action alone.

  The difference between bird and mammal lungs is quite complex, but these are the basic points:

  • mammal lungs have many tiny air sacs called alveoli - bird lungs have a few large air sacs.
  • mammal lungs change volume with each breath - bird lungs have a fixed volume.
  • mammal blood capillaries exchange gas with the alveoli - bird blood capillaries twine around air capillaries where gas exchange takes place.
  • Mammal lungs take air in with one breath and push the same air out with the next breath - bird lungs work in such a way that fresh air flows in one direction through the system.

Raptors:

Birds that have hooked beaks for tearing flesh are called raptors. Two raptors are well known in Oklahoma; the red-tailed hawk, Buteo jamaicensis, and the turkey vulture, Cathartes aura.

Owls are important nocturnal predators in Oklahoma, feeding mostly on small mammals. Three owls are common; the great horned owl, Cathartes aura, the barred owl, Strix varia, and the screech owl, Otus asio. The screech owl feeds most often on insects. Although an owl's keen eyesight is important for hunting at night, their hearing is even more important. Notice where the ear openings are located on the drawing. They are not on the sides where the ear tufts are, but more to the front of the head. They are also positioned at different levels. This allows owls to hear best directly in front of them and gives depth perception to their hearing.

Day 2

What part of the bird's skeleton controls the primary feathers?

Bird classification:

Classification is complicated by the large number of similar bird types. There are close to 9,000 species of birds alive today. Twenty of the approximately 27 orders of birds have representatives in the United States. Most identification characteristics are based on differences in shape and structure of the bill, feet, wings, and tail. However, variations in size, color, and markings are used more for bird identification than any other vertebrate group. That is because most birds attain their full growth within a few months of hatching, and individual variation in adult size is less than 3% of the average species measurement among members of the same sex.

Research Links:

• Red Rock Bird Checklist - Desert Vista High School
• Chordate Anatomy and Evolution - George Washington University

Raptors have hooked beaks for tearing flesh.

The primary feathers are attached to the bird's "fingers".