Tinamiformes

Tinamous () are members of the order Tinamiformes (), and family Tinamidae (), divided into two distinct subfamilies, containing 46 species found in Mexico, Central America, and South America. The word "tinamou" comes from the Galibi term for these birds, ''tinamu''. Tinamous are the only living group of palaeognaths able to fly, and were traditionally regarded as the sister group of the flightless ratites, but recent work places them well within the ratite radiation as most closely related to the extinct moa of New Zealand, implying flightlessness emerged among ratites multiple times. Tinamous first appear in the fossil record in the Miocene epoch. They are generally sedentary, ground-dwelling and, though not flightless, when possible avoid flight in favour of hiding or running away from danger. They are found in a variety of habitats, ranging from semi-arid alpine grasslands to tropical rainforests. The two subfamilies are broadly divided by habitat, with the Nothurinae referred to as steppe or open country tinamous, and the Tinaminae known as forest tinamous.

Although some species are quite common, tinamous are shy and secretive birds. They are active during the day, retiring to roosts at night. They generally have cryptic plumage, with males and females similar in appearance, though the females are usually larger. They are opportunistic and omnivorous feeders, consuming a wide variety of plant and animal food from fruits and seeds to worms, insects and small vertebrates. They will dust-bathe as well as wash themselves by standing in heavy rain. They are heard more often than seen, communicating with each other by a variety of frequently given, characteristic calls, especially during the breeding season.

With occasional exceptions, a male tinamou maintains a territory and a nesting site during the breeding season which a succession of females will visit, laying their eggs in the same nest. Females will wander through several territories mating with, and laying eggs in the nests of, the resident males. Nests are always on the ground, concealed in vegetation or among rocks. Eggs are relatively large and glossy, often brightly colored when laid, and are incubated by the males for a period of two to three weeks. The chicks can run soon after hatching and are largely self-sufficient at three weeks old.

Tinamous and their eggs have many natural predators, from falcons and vampire bats to jaguars. They have also been extensively hunted by humans and sometimes persecuted as agricultural pests. However, the main threat to their populations is from habitat destruction through land clearing and agricultural development. Seven species are listed as vulnerable and another seven as near-threatened. They feature in the mythology of the indigenous peoples of their range. Often translocated and easily bred in captivity, they have never been successfully domesticated.

Taxonomy and systematics

The tinamou family consists of 46 extant species in nine genera. The two subfamilies are the Nothurinae (also known as the Rhyncotinae), the steppe tinamous, and the Tinaminae, the forest tinamous. "''Tinamidae''" was defined as by Gauthier and de Queiroz (2001): "''Tinamidae'' refers to the crown clade stemming from the most recent common ancestor of ''Tetrao'' 'Tinamus''">Tinamus.html" ;"title="'Tinamus">'Tinamus''''major'' Gmelin 1789 and all extant birds sharing a more recent ancestor with that species than with ''Struthio camelus'' Linnaeus 1758 and ''Vultur gryphus'' Linnaeus 1758." Their similarity to other ground-dwelling birds such as partridges and megapodes is a result of convergent evolution, convergence and symplesiomorphy rather than shared evolutionary innovations.

Of Gondwanan origin, tinamous are allied to the flightless ratites, together comprising the Palaeognathae ("old jaws"), while all other living birds are members of Neognathae ("new jaws"). Unlike other palaeognaths, tinamous do have a keeled sternum, but like the other palaeognaths, they have a distinctive palate. It was formerly believed that the Tinamiformes separated from the ratites early on due to their retention of a keeled sternum. The tinamous' possession of powder-down feathers and preen glands, which the other ratites lack, was another source of confusion in evaluating their taxonomy.
The tinamou family has been shown to be monophyletic. Phylogenomic studies have placed it as the sister group to extant Australasian and Oceanian ratites (i.e. the cassowaries, emus, and kiwis), thus putting it well within the ratite phylogenetic tree, with the South American rheas and African ostriches as successive outgroups. Research published starting in 2010 has found that tinamous are closest to the extinct moa of New Zealand; moa are more distantly related to the geographically proximate kiwis, emus and cassowaries than had been previously supposed. These findings imply that flightlessness evolved independently multiple times in ratite evolution. Flight may have been maintained in the tinamou family due to the rhea colonizing South America before ancestral tinamous arrived. The ecological niche for large, flightless herbivores was thus already occupied, forcing tinamous to retain smaller-bodied, omnivorous, and volant lifestyles.

Fossil record

Flight-capable lithornithids from the Paleocene and Eocene epochs appear to have been structurally the most similar precursors to the tinamous, and may have been ancestral to them as well as to the ratites, though their precise relationships are unclear. The earliest unequivocally Tinamiforme fossil material dates from the Miocene, but flightless ratite-like taxa from the Paleocene may belong to this group.

Several tinamou fossils have been found in the 16–17 Mya Early-Middle Miocene Santa Cruz Formation and the contemporary, or slightly older, Pinturas Formation, in Santa Cruz Province of Argentinian Patagonia, including a tinaminid, '' Crypturellus reai''. Associated fossils indicate that the local palaeoenvironment at the beginning of this period was characterised by a humid, subtropical climate, with forest vegetation, becoming drier and more open with time. Some of the tinamou fossil material appears to be intermediate between the two subfamilies, suggesting that the period coincides with the origins of the radiation of the Nothurinae into the expanding open-country habitats.

Nothurine fossils referrable to ''Eudromia'' and ''Nothura'' have been found in the Late Miocene Cerro Azul Formation from the Pampean region of central-southern Argentina. Tinamous described from Pliocene

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