In most tinamou species, the males practice simultaneous
polygyny and the females sequential
polyandry. This is not invariable; ornate tinamous form stable pairs, and spotted nothuras are
monogamous when young and polygamous when older. There are larger numbers of females than males; for example, the variegated tinamou has a female to male ratio of 4:1. The breeding season varies from species to species; those that live in tropical forests, where there is little seasonal change, may breed at any time, though there is usually a preferred period. In areas with marked seasonal fluctuations, tinamous generally breed when food is most abundant, typically during the summer. Studies have shown that it is not day length that determines the onset of breeding, but the amount of light, through cloud cover.
Courtship The
courtship process starts with the male vocally advertising his abilities with continuous calling. He will try to attract multiple females. In
Tinamus species, the male will lower his chest to the ground, stretch his neck forward, and fluff up his back to appear larger than normal. When observed head on, all of the bird's back is in view while the under-tail coverts are exposed, a pose similar to that used by the
rhea. The female will scratch her feet on the ground as part of the ritual.
Nesting Tinamous always nest on the ground; in open areas, near a bush; in scrub, in a dense patch of grass; in forest, at the base of a tree trunk between the buttresses. The highland tinamou is unique in that it sites its nest in a cavity or under an overhanging rock on a steep slope. Many species do not build a nest, choosing to lay their eggs on a thin bed of leaves. Other species construct nests and are meticulous in doing so. The nest of the ornate tinamou is circular and made of grass on a turf surface. The male brushland tinamou starts to scrape out a nest once
copulation has occurred; several may be constructed, though only one is used.
Egg-laying A tinamou female lays several
eggs which the male incubates while the female departs to seek another mate. Large species will lay one egg every 3–4 days, while the smaller ones lay on consecutive days. The females lay eggs in multiple nests throughout the nesting season. There may be as many as 16 eggs in a
clutch, a consequence of several females laying in the same nest. The more mature male will attract more females and may have the eggs of up to four females under him. The variegated and ornate tinamous have single-female nests, and consequently only one or two eggs per nest. This may result from food shortage in their ranges and the consequent ability to care for only one or two chicks. The eggs are fairly deeply colored, usually in a single color, and have a hard
porcelain-like gloss. Colors vary with species, ranging through green, purple, violet, turquoise, steel grey, chocolate and lemon-yellow. White is rare, but does occur. Though the eggs are bright and colorful when laid, over time, they fade and become duller. For example, the egg of the red-winged tinamou dulls from purple to leaden. Most tinamou eggs are solid colored, without spots or speckling; however, the eggs of
Tinamotis species may exhibit small white speckles. The benefit of laying brightly colored eggs is unknown, but is not detrimental as most tinamou predators hunt at night. Eggs are relatively large compared to the mass of the female, though even the largest birds produce eggs very similar in size to the smallest of species. Their shapes are either spherical or elliptical; the two ends are similar in shape and difficult to distinguish. The shells are thin enough to see the embryos within.
Incubation Incubation takes about 16 days in
Crypturellus, which contains the smallest species, and 19–20 days in
Tinamus and
Eudromia. During this period, the male is typically silent; if he does call, he does so away from the nest. As he incubates, he will leave the nest to feed, and he may be gone from 45 minutes to five hours, covering the eggs when he leaves. While incubating, he is mainly motionless and reluctant to move, even from potential danger. It is possible for a human observer to approach and touch the incubating male without eliciting an overt response. Some species will flatten themselves against the ground, stretch out their necks, and raise their backs to the air. This posture causes them to resemble a plant; however, if it is overdone, the eggs become visible from behind. If the male becomes alarmed enough to leave the nest, he will attempt a
distraction display. This usually involves a fake injury display, similar to that of the
killdeer. To do this, he will hop on one leg and attempt to fly, always falling down. He will perform this display if the eggs have not hatched or the chicks are still too young to fly. It is generally believed that tinamous are not as effective at distraction displays as other birds.
Chicks Chicks hatch synchronously with a dense downy coat. The coloring is white, grey or yellow, with dark spots to aid in camouflage. The young are
precocial, and can run almost as soon as they hatch. Soon after hatching the eggs, the male will leave the nest and call the chicks to him with a soft contact call. If threatened, he will freeze and attempt to hide the chicks under his wings or belly. There have been documented cases of females caring for the young; it is thought that this occurs when the male has been killed. Young chicks can feed themselves within the first few days, but the male will bring the food and drop it on the ground in front of them. The chicks have a high initial mortality rate. However, within a few days, they are chasing insects on their own and, at 1–3 weeks, they can fly to branches a metre from the ground. They are self-sufficient within 20 days. By 20 days, the young slaty-breasted tinamou has gained adult size, though not adult weight. The spotted nothura will go from 10% of adult weight to 90% within 85 days, and the red-winged tinamou will do so in 108 days. Sexual maturity comes at the age of one year, although some species may be
physiologically mature by 57 days. However, some behavior may need to be learned before the birds can breed successfully. Once done with the brood, the male, if still within the breeding season, will seek out another female and initiate the cycle again. Studies have shown that 54–62% of breeding female spotted nothura are first-year birds. ==Feeding==