How Do Birds Mate? All About Avian Reproduction

You often catch birds making a nest on your window panes or roof, but you rarely see birds mate. It begs the question, how do birds mate?

Birds copulate to produce eggs, just like other animals copulate to produce offspring. However, the mating process does not make birds pregnant. They don't get pregnant in the ways that mammals do. So, how do birds mate? 

Birds reproduce via internal fertilization. The male bird mounts its mate after performing mating rituals and rubs their cloacal openings together, facilitating the transfer of sperm into the female's ovary. 

Read on as we explore the other reproductive organs birds mate with. We discuss how egg-laying birds mate, where they mate, and how they attract their mating partners. We will also explore the egg-laying birds' incubation process and their relationship dynamics. 

Related Read: Bird Facts.

Reproductive organs of male birds 

We can’t discuss birds mating without mentioning their sexual and reproductive organs. Make birds have a pair of testes located in the abdominal area, near the cephalic border of the kidneys. 

The testes produce sperm at the same temperature as a bird's body temperature. Unlike mammals, they need the scrotum for thermoregulation before sperm development occurs³. 

Both testes aren't the same size because one can be larger than the other, but it is entirely dependent on bird species. Both testes are attracted to the body wall by the fold of the peritoneum (known as mesorchium) and covered by a fibrous inner coat, the tunica albuginea, and a thin outer layer, the tunica vaginalis. 

The testes can increase in weight as a male bird reaches sexual maturity. They weigh between 9 g and 30 g. In seasonal breeders, the testes often increase 300 to 500 times during active reproductive periods.

Although they do have testes, most birds do not have a penis. Only 3% of birds have penises. The species of birds with penises are ducks, ostrich, emu, geese, and swans. 

These bird penises come in different shapes and sizes, and mating only lasts for a brief moment. They insert their organ into the female reproductive part and deposit spermatozoa, while birds without penises have the cloacal kiss⁴. 

An ostrich has a cone-shaped penis with a broad base. Emus have a smaller penis, while Rhea bird species have larger penises. Additionally, waterfowl birds have penises of various lengths. The difference between each waterfowl's penis is a variety of spines and grooves on it. Drake birds have penises that coil along the ventral wall of the cloaca when flaccid but have an elaborate spiral shape when erect and ready for copulation.

Reproductive organs of female birds  

Female birds do not have a cervix as a part of their reproductive system, so the lower end of the oviduct opens into the cloaca. The cloaca has three openings for three purposes. They are reproduction, digestive, and urinary tracts. A female bird develops ovaries at 5 to 10 days old.

However, the right ovary and fallopian tube revert to their undeveloped state, leaving the left ovary and the left fallopian tube for breeding. Some other bird species, i.e., hawks and owls, have two ovaries but don't lay as many eggs as birds with a single ovary. 

For example, a chicken can lay several eggs yearly, but hawks and owls can only produce 2-5 eggs per clutch. 

A bird's oviduct is a complex organ with various sections that convert nutrients from the food eaten. It contributes to the multiple aspects of a well-formed egg. As a female bird near sexual maturity, it experiences early changes associated with high estrogen levels. 

Then, the luteinizing hormone induces ovulation, followed by eggshell clarification under the progesterone control. In female white-throated sparrows, hearing male songs modulates the timing of reproduction by increasing the plasma luteinizing hormone¹. 

Birds need a constant source of calcium for eggshell production. They get it from intestinal absorption from the food they eat, renal control of calcium levels, and the mobilization of bone calcium deposits. 

Hornbill birds can only lay one egg yearly, while gulls lay four eggs. Mallard ducks can produce 9-11 eggs, ostriches can lay a maximum of 15 eggs, and partridges can lay up to 20 eggs yearly. 

How do birds mate? 

After male and female birds perform a courting ritual to attract a mate during the breeding season, the birds settle down to mate. Since most birds do have penises as their sexual organ, how do birds mate? 

Remember, we mentioned earlier that both genders have a cloacal opening. The cloacal hole contains holes used as the sexual organ, urinary tract, and excreta passage. The mating birds perform the sex act through a cloacal kiss. 

The female bird shifts its tail feathers to the side to reveal its cloacal wall. Next, the male bird balances behind, facing the same direction as the female, and connects the male’s cloaca to the female’s cloaca, forming the cloaca kiss. He transfers the sperm into her cloacal wall. 

In some cases, male birds sit on the female bird to mate. Other species with penises do not perform the sex act through a cloacal kiss. They transfer the sperm stored in a nearby sac with their erect penis into the female bird’s cloaca opening. 

Once the sperm enters the cloacal wall, it stays at the lower end of the oviduct for a period before moving to the oviduct’s upper area to fertilize the unfertilized eggs. 

In bird reproduction, mating doesn't have a role in the production of eggs. However, the time birds reproduce determines the rate of egg fertility. Some believe the eggs can delay the journey of the spermatozoa to the fallopian tube, where fertilization happens. The sperm can stay in a part of the reproductive organ known as the spermatozoa storage tubule. 

The spermatozoa storage tubule can hold sperm for three weeks to three months. The storage period depends on the species of bird. Studies show that turkeys lay eggs two months after the breeding season. 

Where do birds mate?  

Birds mate in various locations. Terrestrial birds copulate on land, tree branches, and other perch areas. Some aquatic mating birds, like phalaropes and ducks, perform the sex act in water, while some mate in the air. 

Most birds usually perform aerial displays during courtship rituals but don't mate in the air. For example, the White-throated Swifts is a North American bird that copulates mid-flight. The breeding birds swoop down a canyon at high speed, with the male and female birds tumbling together as they perform a cloacal kiss in the air. 

How do birds attract mates?  

During the mating season, birds display behaviors to attract a suitable mate. These displays show a bird's mating capabilities, like strength, health, and beauty. There are different activities birds perform during mating rituals. They are: 

1. Singing
2. Dance display
3. Nest building
4. Touching and Preening
5. Feeding  

Singing 

Most male birds perform intricate songs, known as the mating call, to woo females. This courtship ritual is one of the most prominent of all mating rituals. Most female birds choose a male bird whose song shows the best display of intelligence and maturity. 

In zebra finches, male songs attract both males and females during the breeding season. It is unlikely in most species because most male mating calls repel other males. The northern cardinal bird also sings to entice a female mate.  

Dance and body display 

This mating ritual involves elaborate physical movements and dance steps to gain the attention of other birds². In some cases, only the male birds dance to flirt; sometimes, the male and female birds dance in unison. They flap their wings and dip their wings in elaborate manners. 

Birds of paradise have the most extravagant dance rituals and costumes. They show off their ornate plumage, head plumes, and tail feathers to woo the female. Birds of paradise with bright and colorful plumages and extra plumage feathers stand a better chance of successful mating with multiple females. 

Male Costa’s hummingbird flirts with his intended by swooping and diving over the perched female. He uses a lot of energy and strength to twist his body in the air, but he still has to do more to impress her as she is not easily impressed. To win her over, he flexes the muscles in his face and spreads out his magenta wings.

Nest building 

Some species of birds build more than one nest to win the attention of a female. Among the house-wren birds, the female has to inspect the male’s nesting site before she accepts to be his mate. 

A female comes to the male territory to view his nesting cavities. Once she finds an acceptable nest, she begins the construction of the nest. It confirms she’s his mate for the upcoming season.  

Bowerbirds are species of birds you can find in New Guinea and Australia. They construct the largest and most elaborate structures to attract mates. 

Touching and Preening 

Mourning dove birds show desire by mutual preening. This ritual consists of birds gently nibbling each other’s head and neck feathers. The male bird may stretch over his shoulders, dig into his shoulders, and move his bill along his neck and breast. 

As a sign of acceptance, the female puts her beak in the male’s open beak, and they bump heads briefly.

Feeding 

Feeding each other is a love language among bird species. Courtship feeding occurs at the beginning of the mating season when the males are trying to get the attention of their favorite female. It also happens during the incubation period right before the baby bird hatches. 

You can witness courtship feeding in Common Tern birds. A male will carry fish around the breeding colony to show the females. He mates with the female who accepts his food offering. 

As the season passes, the female common tern becomes more dependent on the male for food. However, he stops feeding her after laying the third or fourth egg.  

Blue tits birds feed their female counterparts 40% of their diet in the early stages of bird mating before they lay eggs. 

Egg incubation process   

The next step after fertilizing and laying the eggs in a few days is incubation. Incubation is the process of providing the best temperature, air circulation, and relative humidity suitable for embryo development. The process can be a natural one or an artificial incubation. A correct incubation process produces baby birds.  

Wild birds, domesticated birds, and pet birds all incubate their eggs. Sometimes, bird owners have to incubate a pet bird’s eggs artificially. They lay a quantity that their feathers can cover. For example, hens lay up to 13 eggs and sit on them. The hen fusses over her eggs, adjusting them throughout the day. Mother hen doesn't leave the nest until they hatch. 

In some species, both parents incubate the eggs together. In other cases, the male parent incubates the eggs. An example is penguins, a species of flightless birds. The male penguin sits in the eggs while the female penguin searches for food. 

Are birds monogamous? 

Are birds exclusive to a single partner? Yes, birds are monogamous. 90% of the bird species are monogamous⁵. The monogamous bond duration varies. It could last for a single nesting period, an entire or several breeding seasons. Also, birds mate for life. 

Some examples of birds that mate for life include the bald eagle, Laysan albatross, and Atlantic puffin bird. An Atlantic puffin bird reaches sexual maturity between the ages of three to six. A bird chooses its life partner during its first mating season, and they return to the same breeding grounds yearly. They share egg incubating and parenting duties. 

Laysan albatross birds lay eggs when they are nine years old. They mate for life and strengthen their bond with an annual ritual dance. Layasan albatross birds mourn for about two years when they lose their partners to death. However, after two years of mourning, they will try to find a new mate. 

Both the albatross and the Atlantic puffin birds lay one egg per clutch, while the bald eagle lays an average of three eggs per clutch—moreover, the bald eagle mates for life until death.

Some birds practice polygyny. It refers to the act of a male bird reproduction with more than one female, and the females mate with one male. Additionally, there are promiscuous birds that only copulate for some minutes or hours. The female birds lay eggs without the support of the male, becoming a single mother. An example of a polygamous bird is a hummingbird. 

Conclusion 

Birds have elaborate courtship practices that help them select the best partners. How do birds mate since most birds do not have penises? They mate by rubbing their reproductive openings together.  The female’s body only has one ovary used to produce eggs. 

Birds woo their mates by singing, dancing, displaying beautiful plumages, and feeding their crush. In some cases, some birds mate with other species. You have a high chance of seeing birds breeding during the springtime. So, do not disturb a bird trying to hop and balance on another bird.