Family of birds
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"] "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 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 material include "Eudromia olsoni" Tambussi &amp; Tonni, 1985, "Nothura parvulus" Rovereto, 1914, and "Nothura padulosa" Mercerat, 1897. The Pliocene fossil genera "Cayetornis" Brodkorb and "Tinamisornis" Rovereto have been synonymized with "Nothura" and "Eudromia" respectively. Fossils having affinities with several extant genera have been found in Pleistocene deposits.
Generic relationships.
Cladogram of tinamou genera based on a study by Lukas Musher and collaborators published in 2024.
Species in taxonomic order.
Conservation status key:
Order Tinamiformes [Crypturi ; Dromaeomorphae ]
Family Tinamidae
Description.
Tinamous are plump, compact birds with slender necks, small heads and, usually, short, decurved bills, though a few have long bills. Females are usually larger than the males. The smallest species, the dwarf tinamou, weighs about with a length of . Females of the largest, the grey tinamou, weigh up to with a length of up to . Their feet have three forward-facing toes; a hind toe is either higher and retrogressed, or absent. The back of the tarsus is covered with scales, the color of which may aid in identification.
Tinamous have a pneumaticized skeleton with a sternal keel, 16–18 cervical vertebrae, and fused thoracic vertebrae. They have poor circulation, evidenced by a greenish tint to the skin. They also have relatively the smallest hearts and lungs of all birds, comprising only 1.6–3.1% of their body weight, whereas the equivalent in a domestic chicken is 12%. Despite their poor flying ability, the percentage of their body mass that is muscle is 28.6–40%, which is similar to that of hummingbirds. The preen gland is small and tufted. The male has a corkscrew shaped penis, similar to those of the other ratites and to the hemipenis of some reptiles. The female has a small phallic organ in the cloaca which becomes larger during the breeding season.
Plumage.
The plumage of the family is cryptic, as is usual with ground birds, with typical colors ranging through dark brown, rufous, buff, yellow and grey. Plumage does not usually differ between sexes, but in a few species females are brighter. The forest dwellers tend to be darker and more uniform, whereas the steppe species are paler with more barring, speckling, or streaking. Tinamous have well-developed powder down feathers; these grow continuously and disintegrate at the tips into a powder that is spread through the rest of the feathers by preening. This gives the plumage a glossy appearance as well as waterproofing it. Their tails are short, sometimes hidden behind the coverts, and possibly indicative of an ability to sacrifice feathers to a predator in order to escape when grasped. Some tinamous have crests. Members of "Eudromia" have the most developed crests and, when excited, will direct them forward.
Voice.
Tinamous are rarely seen but often heard within their range and have a wide variety of calls. They are among the most characteristic bird vocalizations of South America and Central America, often resembling sounds made by a flute or a whistle. Some calls are uniform and monotone, while others have multiple phrases. They vary in intensity and can often be heard from afar. Trying to locate a bird by its call is not easy.
Plains-dwelling tinamous have higher-pitched, more delicate voices. They can also be less melodic, sometimes resembling the chirps of crickets. Forest species tend to have deep, loud calls, suitable for penetrating the vegetation. The male highland tinamou can be heard several kilometres distant through dense forest. When calling, a tinamou extends its neck vertically, tilts its head at an angle, and opens its bill wide. A bird, when flushed, will utter a sharp trill.
Identification of tinamous is not an easy task; utilizing their calls as a tool is integral. Each species has its own unique call or calls. The solitary tinamou has 11 different vocalizations. In most species both sexes call; some have different calls for males and females. Females tend to have deeper voices. Some species, in particular members of "Crypturellus", have regional dialects. Male slaty-breasted tinamous have calls unique enough to be individually recognized by humans.
Calls are typically heard more frequently during the breeding season. However, the time of day can differ amongst species, as some are more vocal in the morning, others in the evening, and some are more vocal during the heat of midday. Some will call at night from their roosts. Frequency can vary between species and between individuals. One male brushland tinamou called every few minutes from dawn until dusk (over 500 calls daily). Some, in particular "Crypturellus" species, use regular call sites. Only a few possess an alarm call.
Distribution and habitat.
Range.
Tinamous are exclusively neotropical and all 47 species live in South America, Mexico, and Central America. The range of the northernmost species extends to Mexico but not much further north than the Tropic of Cancer. Chilean tinamous have been introduced to Easter Island. The greatest concentration of species is in the tropics, and in particular the Amazon Basin. In the north, they tend to be forest or woodland birds, while in the south they prefer open habitats. Tinamous form the dominant group of terrestrial birds in South America, where they largely replace the Galliformes ecologically, with no other bird family there having comparable diversity, distribution, or suite of habitat adaptations. Rheas are only found in open country, curassows and guans are generally limited to forests, and the pheasant family is only represented by a few species in the north of the region.
They occur in a wide range of habitats. Members of the genera "Tinamus", "Nothocercus", and "Crypturellus" live in dense forests, with "Nothocercus" preferring high altitude, and members of most other genera in grassland, puna, montane forest, and savanna. "Tinamotis" and "Nothoprocta" prefer high altitude habitats, up to , whereas the other steppe tinamous have a wide altitude range. Tinamous inhabit most parts of South and Central America, as well as the tropical regions of Mexico, with the exception of aquatic, snow-covered, and true desert habitats, and the southernmost tip of Patagonia.
Ecology.
Behavioral and ecological separation of tinamou species is evident where their ranges overlap through the utilization of different food sources and occupation of limited micro-habitats. These micro-habitats are not always easy to identify, and are highly vulnerable to environmental changes. Some species, such as the red-winged tinamou, utilize multiple habitats such as the open savannas of Amazonia and the dry valleys of the Andes. Similarly, brown tinamous occur in both the Amazon basin and the humid montane forests on the Andean slope.
Panama provides examples of ecological separation. The highland tinamou occupies the highlands throughout the country. The great tinamou prefers the rainforests on the slopes.