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In the world today, there are roughly 8,600 species of birds, and about 100 billion birds in the world. Birds have an extraordinarily sleek body frame, and their bodies are sheltered by feathers. There are many birds that have very colourful feathers, while others are barely even noticeable to the naked eye due to their plain and unadorned appearance. The front limbs of birds are modified into wings enabling most birds to be able to fly. Birds generally have four toes on their hind limbs. The jaws of birds are covered by a horny style beak and a bird's weight can vary significantly.
Birds and Reproduction
Birds reproduce by sexual reproduction. Many birds have courtship rituals. Male and female birds from many bird species develop pair bonds. They actually remain with one another throughout the reproductive season. The male bird's sexual organs consist of paired testes. The female bird's sexual organs consist of only a left ovary and oviduct. This left ovary and oviduct is the only functional ovary that the female birds have.
The Male Bird's Sperm
During sexual reproduction, the male bird's sperm passes out of the testis and into the vas deferens. The vas deferens is a duct that expands near the cloaca into a storage organ. The cloaca is a common chamber that receives digestive wastes and urogenital products such as urine and gametes. This is common in most vertebrates.
Coitus and Birds
Some male birds actually have a sexual organ much like a penis. Some of these include anseriformes, the cracidae and the tinamidae. The act of coitus generally may only last a few seconds with birds. However, the length of coitus depends on the species of the bird. During coitus, the male is generally mounted on top of the female's back.
The Laying of Eggs
Once the male bird deposits his semen into the female bird's cloaca, the female birds lay sets of eggs. These eggs are referred to as clutches. The eggs are laid in distinct groupings in plainly distinct nests. These nests can vary from formations of simple grazes in the ground to very highly structured nests.
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