Whether it’s late winter for owls and eagles, spring for most songbirds, summer for goldfinches, or whenever conditions are right for many pigeons and doves, the breeding season is a busy one for birds. But before birds can get busy with baby chicks, they have to “get busy” with mating. Just how do birds have sex?
Bird Reproductive Anatomy
Birds do not have the same familiar sexual organs as mammals. Instead, both male and female birds have a cloaca (also called a vent). This one opening is the exit for the digestive, urinary, and reproductive tracts. Male birds do have testes and female birds have ovaries, but these organs change throughout the year. During the breeding season, which is triggered not only by seasonal light levels and climate, but also by resource and food abundance, the testes and ovaries will grow and begin producing sperm and ova. At the same time, the cloaca swells and the birds will be ready to mate.
The hormonal changes that cause the sexual organs to become ready for mating also trigger behavioral changes. At this time, birds become more aggressive about protecting territory. They will be inspired to exhibit courtship behaviors such as dances, singing, and plumage displays that will help attract the best mates.
After the breeding season ends, birds’ sexual organs recede and shrink. This reduces the weight of those organs in preparation for migration. Unlike humans, birds will not mate outside of the most productive seasons. Outside the breeding season, their competitive behaviors are also reduced.
How Birds Mate
When birds are ready to mate, males and females will seek out the best possible partners. Once they have found a suitable mate, the sex act is surprisingly quick. The typical posture is for the male to balance on the female’s back, with both birds facing the same direction. The female may bow, crouch, hunch, or even lay on the ground to make access easier for the male. The male will then hunch or arch in order to touch his cloaca to hers. That simple contact lasts only a second. That’s long enough for sperm to transfer from the male’s cloaca to the female’s. There, it will then travel up the short passage to fertilize her ova and egg formation will begin.
See also: A Bird Nest is an Engineering Marvel
The touching of cloacas between male and female birds is called a “cloacal kiss.” Birds may exchange several of these “kisses” during one mating session to ensure fertilization. The female may store the transferred sperm in her cloaca for several days, weeks, or months, until the conditions are right for her to begin laying eggs.
After the sex act is complete, the male and female birds may completely part company. The male will often have no further part in reproduction or caring for any chicks after hatching. Most hummingbirds, for example, have no partnerships and the male birds do not help females with family duties. When birds do stay in committed pairs, such as northern cardinals and many other songbirds, both partners may work together to build a nest, incubate the eggs, and care for the chicks. Some birds, such as bald eagles, will stay together for years to raise new chicks each year.
See also: Bald Eagle Facts and Trivia
Waterfowl Mate Differently
The general mating process is the same for most types of birds, including hummingbirds, warblers, jays, sparrows, shorebirds, raptors, penguins, and ostriches. Waterfowl, however, mate somewhat differently. Many geese, ducks, and swans do have a phallus. These birds mate in water, and a male will hold a female underwater briefly as he inserts his phallus into her cloaca for insemination. This helps keep the sperm from washing away in the water and can make mating more successful. As with other birds, however, the sex act is still just a brief encounter.
When You See Mating Birds
It can be startling to witness birds mating, and many birders don’t recognize the behavior right away. If you do see birds having sex, however, it is important to keep your distance and not disturb their actions. If birds are frightened or stressed while mating, they may not complete their bond and the mating could be less successful. Birds might even abandon an otherwise ideal habitat where they could have raised their young, and without the best resources and food supplies, the chicks may have less chance of survival. If you’re able to recognize birds’ mating, however, you can not only appreciate the opportunity to witness such an amazing behavior, but stay alert for the next few weeks and see the entire life cycle as a nest is built, eggs are incubated, and young birds hatch and begin to explore their new world.