How do birds mate?
Most birds mate with a "cloacal kiss". The male balances on the female's back, she moves her tail to one side, and they press their cloacas together for about a second while sperm passes from male to female. The cloaca is the single opening birds use for reproduction and waste. About 97% of bird species have no penis, so there is no penetration.
First, abandon all you know about mammalian sexual organs. A bird's reproductive anatomy is far simpler. There's pretty much only one position that works, given where the cloaca sits: the male on top of the female, both facing the same direction. She hunches down and moves her tail feathers aside, while he arches or curls his body downwards so that their cloacas touch.
The male has already produced sperm and stored it in the folds of his cloaca. Pressing the two openings together moves the sperm into the female, where it travels on to the ovary. Once an egg is fertilised, egg formation begins. Depending on the species, eggs can be ready to lay within days or take weeks.
"Abandon all you know about mammalian sexual organs."
Courtship, on the other hand, can be spectacular. Read more about bird mating rituals, why birds sing during the breeding season, and whether birds fall in love.
What is a cloaca?
The cloaca, or vent (pronounced kloh-AY-kuh), is a single opening under a bird's tail. It leads to a chamber connected to the reproductive organs (testes in males, ovaries in females), the urinary system and the gut. Both male and female birds have one. It swells during the breeding season and is barely visible the rest of the year.
Hormones make the cloaca enlarge until it protrudes from the feathers, reaching its peak size just when it's time to mate. Outside the breeding season it's almost impossible to see. Researchers fitting a leg ring or a tracker sometimes blow gently on the feathers to part them: in many songbirds, a swollen bump at the cloaca during the breeding season means they're holding a male.
How long does bird mating take?
The cloacal kiss itself usually lasts less than a second. Keeping balance can slow things down, and a pair may touch several times in one session. Most pairs mate repeatedly over several days around egg-laying, which raises the chance that the eggs are fertilised.
"The act of the cloacal kiss usually takes less than a second."
After that, it depends on the species. In some, the male leaves and may find another mate. In others he stays to help raise the chicks, until they hatch, until they fledge, or for life.
Do birds stay with one mate?
Most songbirds pair up for one breeding season, and some birds, such as swans and many geese, often stay together for years. But staying together isn't the same as being exclusive. In many species, females also mate with other males, so eggs in one nest can have different fathers.
Some females even lay eggs in other nests of their own species. Nests of the same species look alike, so it's perfectly ordinary for a bird to raise chicks from different parents without knowing it.
Which birds have a penis?
About 3% of bird species have a penis: ducks, geese, swans and other waterfowl, plus ostriches, emus, rheas and their relatives. A bird's penis is an extension of the cloaca wall that fills with lymph rather than blood. Even then, mating is over in seconds.
You know when a teacher told you one thing, and years later you found out it wasn't the whole truth? So, I've told you birds don't have penises. Confession time: ducks do. There, I've said it.
Waterfowl mate in the same position as other birds. Scientists still debate exactly why they kept a penis when most birds lost it. One idea is that mating on water makes a simple cloacal kiss unreliable: the male's weight pushes the female low in the water, so a more assured method of passing sperm helps.
When do birds mate?
In North America, most backyard birds mate from late winter through summer. Longer days trigger the hormones that start courtship, and food becomes easier to find. Northern cardinals and black-capped chickadees start courting in late winter, American goldfinches nest as late as July and August, and great horned owls nest in the middle of winter.
As winter ends, temperatures rise, days grow longer and food becomes easier to find. Hormones surge, courtship displays start everywhere, and birdsong fills the mornings as males compete for a mate. Mourning doves are an exception to the usual calendar: in the southern US they can breed in almost any month.
Can you see bird courtship at your feeder?
Yes. Watch for courtship feeding: a male northern cardinal passing a seed beak-to-beak to the female is one of the most common sights in late winter and spring. Male house finches feed their mates too, and mourning doves preen each other. Mating itself usually happens near the nest, away from busy feeders.
A camera feeder like Birdbuddy captures these moments up close, so you can catch courtship feeding even when you're not at the window. Early spring is the best time to watch.
Why give mating and nesting birds space?
Mating is brief, but for birds it's a matter of life or death. Disturbing a pair while they mate or build a nest can make them abandon it. If you know where birds are nesting, keep your distance in the first weeks of spring and stay quiet nearby.
If you're the type to blush when you see birds mate, don't sweat it: the birds appreciate the privacy. Watch from indoors or from a hide if you can. Better still, identify the birds you saw, read up on their life cycle, and listen for the cheeping of new chicks. If you're lucky, you'll be there when they finally fledge, a remarkable thing to witness.
FAQ
Do birds have a penis?
Most don't. About 97% of bird species mate by pressing their cloacas together. The exceptions are waterfowl such as ducks, geese and swans, plus ostriches, emus and their relatives.
How long do birds mate?
The contact itself usually lasts under a second. Pairs often repeat it several times in a session and over several days around egg-laying.
Do birds mate for life?
Some do, such as swans and many geese. Most songbirds pair for one season, and even paired birds often mate with others, so a nest can hold eggs from different fathers.
What time of year do birds mate?
In North America, mostly from late winter to summer, when days lengthen and food increases. Great horned owls nest in winter, and goldfinches nest as late as August.
Can birds mate while flying?
Almost all birds mate perched or on the ground. Common swifts, which spend most of their lives in the air, are reported to mate on the wing.
