Tinamous are promiscuous, not staying with one mate during the breeding season. Typically, females visit males, mating and then laying a few eggs in each nest. In some species, females form cooperative groups that travel around laying eggs for various males. So, most male tinamous end up mating with several females. Their nests of grass and leaves fill up with eggs from more than one mate. While the male incubates the large set of eggs, females move on to look for other males. When the eggs hatch, the male tinamou alone takes care of the offspring, which is unusual for birds. His job is not too intensive, as the young are born well-developed (precocial). They can run around within a few hours and fly within a few weeks. However, like tinamou adults, they spend a lot of time on the ground. When in danger, they freeze, counting on their camouflage coloration to keep them hidden.

All modern birds have bills and no teeth. The shape of a bird's bill says a lot about what it eats, for example whether it specializes in seeds (stout , cracking bill), fish (pointy, spearing bill), or plants (wide, serrated bill). Birds swallow their food without chewing, so it travels to the stomach whole or in large pieces. Bird digestive tracts have some special features for digesting chunky food. A pouch in their throat (the crop), is used to store food to be digested later, or regurgitated to feed the young. An extra, muscular stomach (the gizzard) grinds food up. Birds are endotherms, using heat they make internally to keep warm. While a few species allow their body temperature to drop at night (torpor), a nearly constant body temperature is maintained by most birds most of the time. Continuously making heat requires fuel to burn, in the form of food. So, birds spend a lot of time eating.