Avian flight demands more supply of oxygen. As pigeon is a flighting animal the respiratory system of pigeon is more complicated than other groups of vertebrates. Respiration is by means of lungs. Lungs are small in size and supplemented by air sacs which reduce the body weight. Expiration is more active than inspiration.
In Pigeon the Heart lies in the pericardium and situated in the thoracic cavity whereas in Rabit the Heart is enclosed with in the pericardium and placed in the thoracic cavity.
Once there lived a rich man. He was very kind and generous man. He gave away a part of his income in charity. He showed special kindness to the animals and birds. One day, a pigeon entered his kitchen and built her nest in an empty vegetable basket.
The body is spindle shaped. The size varies from 20-25 cm. The body is divisible into head, neck, trunk and tail. Most part of the body is clothed in feathers.