Tinamiformes

A unique family, the tinamous probably represent a very early branch of the evolutionary family tree of birds. Although at a first glance they resemble other terrestrial birds such as quails and partidges, their nearest relatives are thought to be ratites (ostriches, emus, and relatives), although their lineage is perhaps even older. Tinamous retain very primitive characters, including reptilian-like blood proteins and palate structure. However, unlike the flightless ratites, they have a well-developed keel and pectoral muscles, and they are capable of brief but strong flights. 

Additional information

Tinamous have a unique feather structure, in which the barbules of each feather are securely joined rather than hooked (as in other birds). The back and rump feathers are losely attached; it may be that when a predator tries to capture a bird, these loose feathers come away, enabling the bird to escape and leaving the predator with only a mouthful of feathers.

Tinamous are terrestrial and secretive. Most forage by picking food from the ground or vegetation. When threatened, a tinamou will freeze, walk or run away, or explode quail-like from the ground with whistling wings. At the nest, the male freezes even when the intruders come very close. As a last resort, if the nest or chicks are threatened, he uses a distraction display to lure intruders away.

Because these birds have the smallest heart, relative to body size, of any bird, in combination with their small longs, they become exhausted rapidly when pressed to run or fly. 

Taxonomy

There are two subfamilies, mainly differing by the location of the nostrils on the bill: about midway down in the Tinaminae, and at the base in the Rynchotinae.

Number of genera: 9

Number of species: 47

A list of all the species can be found here.