Ducks, like all birds, do not experience pregnancy in the way mammals do. Pregnancy, or viviparity, involves carrying a developing fetus internally for a prolonged period. Ducks instead reproduce through oviparity, the process of laying eggs. These eggs contain all the necessary nutrients and protective layers for the embryo to develop outside the mother’s body. This difference means the creation of new life involves rapid internal assembly followed by external incubation.
Why Ducks Do Not Get Pregnant
The term “pregnancy” describes the state of a female mammal carrying a developing embryo or fetus within her uterus, where it receives nourishment and oxygen directly from the mother’s circulatory system. Ducks lack the specialized organs, such as a uterus and placenta, required for this internal gestation. This difference is rooted in the evolutionary divergence between mammals and birds. For ducks and other egg-laying animals, the closest biological term is “gravid.” A hen duck is considered gravid when she is carrying a fully formed egg in her oviduct, just prior to laying it. The gravid state is fleeting, lasting only a short time before the egg is laid. This contrasts sharply with the many months of mammalian pregnancy.
Internal Fertilization and Reproduction
The reproductive process in ducks begins with internal fertilization, which is required for the production of a fertile egg. Following mating, the male’s sperm travels up the female’s reproductive tract to a specialized region known as the sperm storage tubules (SSTs). These microscopic glands, located near the junction of the oviduct and the cloaca, allow the female duck to store viable sperm for a significant period, often up to two weeks or even longer in some species. This sperm storage capability means that a single mating event can result in the fertilization of multiple eggs laid over many days.
The female reproductive system features only one functional side, the left ovary, which releases the yolk, or ovum, when it is mature. The yolk is released into the infundibulum, the funnel-shaped entrance of the oviduct. If sperm are present, fertilization must occur in the infundibulum, typically within minutes of the yolk’s release. Once the yolk is fertilized, the process of packaging the embryo into a protective egg begins immediately.
The Detailed Process of Egg Formation
After the yolk is released, its journey through the oviduct takes approximately 24 to 27 hours for the complete egg to form.
The first stage is the infundibulum, where the yolk remains for about 15 minutes. The yolk then moves quickly into the magnum, which is the longest section of the oviduct. In the magnum, the thick, protein-rich albumen, or egg white, is secreted and deposited around the yolk, a process that takes about two and a half to three hours. The albumen provides both cushioning and a source of protein for the developing embryo.
Next, the egg travels into the isthmus, where the inner and outer shell membranes are added to enclose the albumen and yolk. The formation of the shell membranes takes roughly one to two hours, giving the egg shape and structure.
The final, longest stage is the shell gland, also called the uterus, where the egg spends about 20 hours. Here, the hard outer shell, composed primarily of calcium carbonate, is deposited, and any shell pigments are applied in the final hours.