What is the Difference Between Avian and Mammalian Reproductive System

The key difference between avian and mammalian reproductive system is that the avian reproductive system facilitates internal fertilization, but the development of the ovum takes place outside the mother’s body, while in the mammalian reproductive system, the fertilization of the ovum and development of the embryo takes place inside mother’s body and directly the offspring is born.

Reproduction is a way of producing offspring or new generations. The reproductive system ensures fertilization up to the process of developing the offspring. It consists of important organs in both males and females needed for reproduction.


1. Overview and Key Difference
2. What is Avian Reproductive System
3. What is Mammalian Reproductive System
4. Similarities – Avian and Mammalian Reproductive System
5. Avian vs Mammalian Reproductive System in Tabular Form
6. Summary – Avian vs Mammalian Reproductive System

What is Avian Reproductive System?

The avian reproductive system is a heterosexual system where the contribution of both male and female are required for the genetic constitution of the offspring. The male contributes his half by the sperm, and the female contributes her half in the ovum. The ovum is usually referred to as the blastodisc or blastoderm. After the yolk is released from the follicle of the ovary, it moves into the oviduct. Aves are considered oviparous since they produce offspring by means of eggs.

Figure 01: Avian Reproductive System

The male reproductive system in aves consists of two testes. Testes produce hormones called androgens, which stimulate the secondary sexual characteristics in aves. Each testis contains a deferent duct, which leads to the cloaca from the testes. The testes are bean-shaped and situated against the backbone in the front of the kidney. The size of testes becomes larger when the birds actively mate. The left testis appears larger than the right. On the inside of each testis, a small, flattened area called the epididymis is present. The deferent duct starts from the epididymis. However, Aves do not have a penis.

The female reproductive system of aves consists of the ovary and oviduct. The female embryo of birds possesses two sets of productive organs but, only one set survives to produce eggs when it reaches maturity. The ovary is situated in front of the kidneys in the abdominal cavity and is strongly attached to the cavity wall. The ovary consists of blood vessels to ensure the transport of nutrients to the developing yolk without any obstruction. The female reproductive system produces hormones such as androgen, oestrogen, and progesterone to control body functions.

What is Mammalian Reproductive System?

Most mammals are considered viviparous since they give birth to live offspring. Viviparous mammals are of two types as marsupials and placental. Marsupials have a short gestation period and give birth to an underdeveloped newborn within a pouch or sac located near the mother’s abdomen, and further development takes place inside the pouch. Placental mammals give birth to fully developed offspring after a long gestation period.

Figure 02: Female Reproductive Organs in Mammals

In placental mammals, the male reproductive system contains the penis, scrotum, testes or testicles, epididymis, and other accessory organs located internally. The penis is the male organ for sexual intercourse. It consists of a urethral opening to transport both semen and urine out of the body. The scrotum is the pouch-like sac of skin located behind the penis. It holds the testes. Testes exist in pairs and must be at a slightly cooler temperature for the production of sperm. They produce the hormone testosterone. The sperms are produced inside the testes and are stored in the epididymis until ejaculation. Other important accessory organs are vas deferens, ejaculatory duct, urethra, seminal vesicles, prostate gland, and Cowper’s glands.

The female reproductive system of mammals includes ovaries, oviducts, uterus, and vagina. Ovaries produce and develop eggs. They also produce female sex hormones oestrogen and progesterone. Oviducts or fallopian tubules transport eggs to the uterus. It also acts as the site of fertilization. The uterus is the site where the embryo develops. Vagina receives the penis during intercourse and acts as the birth canal. The mammary glands of mammals are specialised to produce and deliver milk for the offspring through breasts.

What are the Similarities Between Avian and Mammalian Reproductive System?

  • Avian and mammalian reproductive systems have the contribution of both males and females.
  • Males produce sperms, and females produce eggs.
  • Males possess testes and epididymis in both systems.
  • Females possess ovary and oviduct in both systems.

What is the Difference Between Avian and Mammalian Reproductive System?

The avian reproductive system permits internal fertilization, but the ovum develops and survives outside the body, whereas mammals directly give birth to the offspring. Thus, this is the key difference between avian and mammalian reproductive systems. Moreover, the nourishment of the embryo in mammals takes place through the placenta while the avian embryo is nourished by itself outside the mother’s body. Also, mammals usually feed the young with milk produced in the mammary glands while aves feed the young by regurgitating partially digested food.

The below infographic presents the differences between avian and mammalian reproductive system in tabular form for side by side comparison.

Summary – Avian vs Mammalian Reproductive System

The avian reproductive system facilitates internal fertilization but, the ovum develops and survives outside the body whereas the mammalian reproductive system directly gives birth to the offspring. This is the key difference between the avian and mammalian reproductive system. The avian and mammalian reproductive systems are heterosexual; therefore, both males and females are needed for the production of offspring. Males produce sperms that carry the paternal genetic materials, while females produce ova that carry maternal genetic materials to the offspring. So, this summarizes the difference between avian and nammalian reproductive system.