Bird Reproduction

Bird reproduction begins, as in mammals, when an egg, or ovum, is fertilized in the oviduct by contact with a sperm cell.

The fertilized ovum forms the nucleus of the egg, which will be equipped with a food source (the yolk) and a protective shell before laying.

Bird Reproduction Systems

Certain domesticated birds like chickens and ducks regularly lay eggs without receiving sperm from the male - the eggs we buy in the grocery stores are unfertilized eggs.

As yet another adaptation for lightness, the male's testes only enlarge when producing sperm; then they become several hundred times the normal size.

Sperm passes to the cloaca in a coiled tube, where it is often temporarily stored. The resulting bulge in the cloaca is used by ornithologists to judge a bird's breeding condition. We use cloacal scores to record breeding condition at our MAPS banding stations. We have a scoring method to record the cloacal protuberance condition: 1=conical, 2=tubular, 3=bulging. It is a gradual progression as the male comes into breeding condition.

The female has two ovaries, except in raptors, where it varies individually. Usually only the left ovary develops and like the male cloaca, shrinks after producing the season's ova - another probable adaptation for lightness for bird reproduction.

Sperm is transferred to the female during copulation by direct contact of the two cloacas. The male briefly stands on the back of the female while the cloacas are pressed together (the "cloacal kiss").

Along with bird skeleton, learn about other Bird Characteristics including Feathers, Bird Flight, Bird Song, Beaks, Bird Skeleton and more.

Return to top of Bird Reproduction

Go to Birdwatching Bliss Home Page

Bird Watching Binoculars, Squirrel-Proof Feeder & Bird Bath Heater
bird watching binoculars nikon monarch
Nikon Monarch 5
Best mid-priced bird watching binoculars. Waterproof, shockproof, multi-coated ED-Glass.
best squirrel proof bird feedeR
No batteries, adjustable, easy to clean...and no squirrels!
"Best New Product" Award.
bird bath heaters review
Bird Bath Heater
Provides water source for birds during winter.
Heater operates only when necessary.
Click Images or Links To View More Info
For the Latest Bird Watching News, Hot Birding Spots, Tips & More, Subscribe to Our FREE Newsletter: The Birder Alert!
Enter Your Email

Don't worry — your e-mail address is totally secure.
I promise to use it only to send you The Birder Alert!.
share birdwatching tips

footer for Bird watching page