Site hosted by Angelfire.com: Build your free website today!

Female Reproduction System

Just like many other female animals, the avian female begins life with two ovaries and oviducts. However, in most species of birds, the left ovary and oviduct grow more rapidly than the right, and the right side regresses, leaving only the left ovary and oviduct. Some believe that this is an adaptation to reduce weight, necessary to aid flight. At hatching, the left ovary contains all of the egg cells it will ever have. These cells will continue to develop once the hen reaches an age when she is able to reproduce.

Female birds may have determinate or indeterminate egg layers. Determinate layers are for those birds that only lay a set number of eggs (such as crows or budgies.) Indeterminate layers (such as parrots ) will quickly replace any eggs that are lost, thus not laying a set number of eggs. Breeders utilize this by removing eggs and artificially incubating them, thus encouraging more eggs to be laid.

The female reproductive tract is divided into several parts. It takes approximately 25 hours for an egg to travel from the beginning to the end. The first part of the female reproductive tract is the “infundibulum.” This consists of a funnel which captures the ovulated egg and a tubular region known as the “chalaziferous” region. Sperm fertilizes the egg in the funnel portion of the left oviduct. However, a female will lay eggs even if there has been no mating to fertilize them. In the chalaziferous region a layer of albumen and the “chalazia” are secreted by glands in the tubular region, these help suspend the yolk(beginning of the egg) The egg remains in the 1st part of the reproductive tract for 15 minutes.

The second part of the oviduct is the magnum. It is very thickwalled and contains many tubular glands which secrete albumen, sodium, magnesium and calcium to help with formation of the egg. The egg remains in the magnum for three hours.

The isthmus is a short portion of the oviduct. During the 75 minutes the egg remains here, the inner and outer shell membranes which line the shell are formed and calcification(the formation of the hard outer shell) is initiated.

The uterus is the place the egg remains the longest, from 20 - 26 hours. The shell of the egg finishes here and watery solutions are added to the egg.

The final part of the female reproductive tract is the vagina. The egg passes through this as it is laid. Sperm may be stored in specialized glands known as sperm host glands which are located in the vaginal sphincter for a few days. The sperm travel up to the infundibulum to fertilize the egg.

A majority of birds lay an egg every 24 hours during their laying cycle.

The ovary is under complex hormonal control. In birds that are seasonal egg layers, the left ovary undergoes three phases of development.1. The ovary enlarges. 2. Ovulation and egg laying occur.3.The period which the ovary regresses in size until the next time.