The bird is a vertebrate whose body plan is adapted to its requirements for flight. For example, the skeletal system is lightweight and very strong. The flight muscles of the chest may make up one fifth of the total mass of a bird's body.
Birds have extremely great energy requirements because of their high metabolic rate.
The unique air sacs of their respiratory system provide them with a continuous supply of oxygen. In line with their needs for a streamlined, lightweight body, birds' reproductive organs are small and inactive for most of the year. During the breeding season, however, the male and the female reproductive organs increase greatly in size. In this investigation, you will be exploring some of the unique structural features of a bird through a dissection. The bird under study, found in great numbers in North America, may be either a pigeon or a sparrow.