Tinamiformestinamous

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Tinamiformes comprises one family (Tinamidae), nine genera, and 47 species. Tinamous are restricted to the Neotropics where they occupy a wide variety of habitats. Some dwell in primary tropical rain forests, others reside in scrubby woodlands or forest edges, and yet others inhabit arid or semiarid steppe scrub or grasslands (up to 4-5000m).

Tinamous are superficially chicken-like in appearance. Plumage coloration ranges from light or dark brown to gray, often with dark spotted or barred patterns. The sexes look alike, although females may be slightly larger with more pronounced plumage patterning. Physical characteristics include: small head with thin decurved bill; long slender neck; heavy body (weight 150g-2kg; length 15-50cm); short wings and tail; thick, medium long legs; three short front toes and one backward pointing toe (hallux) which is either elevated or absent. Tinamous have paleognathous (dromaeognathous) palates (broad vomer preventing the basisphenoidal rostrum from articulating with the pterygoids and palatines). They are volant (capable of flight); the skeleton is pneumatic, with a sternal keel (carinate sternum), 16-18 cervical vertebrae, and fused thoracic vertebrae. The basipterygoid process originates from the basisphenoid and articulates with pterygoids. Eutaxic (or quincubital; fifth secondary present), nostrils are either holorhinal (nostril entire, not deeply cleft) or schizorhinal (posterior edge of the bony nostril cleft to or beyond the premaxillaries), nares are impervious (nasal septum present), uropygial gland (oil gland) is small and tufted.

Tinamous forage on the ground and may dig for food items with the bill. The diet consists primarily of seeds, roots, fruits, and arthropods (insects, spiders, termites, ticks), but some species eat small vertebrates (lizards, frogs, mice). Predators of tinamous include humans, foxes, armadillos, and skunks.

Tinamous are considered polygynandrous. At the beginning of the breeding season males establish and defend territories, and females may form coalitions (up to four females) to search for males. Mating displays may occur once the females locate a potential mate. The male mates with each female and the females each lay three or four eggs in that male's nest, then the females depart to mate with and lay eggs for a subsequent male. Males incubate (17-21 days) and then provide brood care for one to two months. Chicks are nidifugous (precocial) and feed themselves shortly after hatching.

Tinamou eggs are noted for their beautiful glossy and deep monochromatic colors from red or purplish black to sky blue or bright green. Nests are shallow depressions in the ground, often located near the base of grasses or trees. The breeding season is well defined (four months) in some species, whereas others may breed year round. Clutch sizes range from 1-16 eggs, with larger clutches likely the result of multiple females laying at the same nest.

Tinamous are primarily ground dwellers able to walk and to run rapidly. They are weak fliers with clumsy but swift flight for short distances. Most species roost on the ground although some roost in trees. Tinamous may avoid predation by standing or crouching motionlessly, or by walking inconspicuously into dense vegetation. If discovered or alarmed, however, they often fly out from a hiding spot with a characteristically noisy burst of wing beats and drop into concealing vegetation a short distance away.

Tinamous are considered primarily solitary, but outside of the breeding season may gather into small foraging parties, family groups, or flocks of up to 100 adults. Female coalitions appear stable and may persist for several years. Vocalizations consist of stereotyped, polysyllabic whistles. Calls of males and females are similar, yet discernible.

Some tinamous are hunted for their meat, which is prized for its tenderness and flavor. In the early 1900's tinamous were raised as game birds in Europe and Canada. Frozen tinamous from Argentina were sold in the USA as South American Quail. Some tinamous are deemed suitable for egg production, but despite successful reproduction in captivity in Europe, domestication has not succeeded. Eleven tinamous species are included in the IUCN Red List of Threatened Species, two of those (Crypturellus saltuarius, Nothoprocta kalinowskii) are listed as Critically Endangered. Major threats to wild populations include: habitat loss and degradation; hunting and collecting; alien invasive species; and land/water pollution.

Traditionally, tinamiform birds are grouped with other paleognathous birds (rheas, ostriches, emus, cassowaries, kiwis) and taken together form a larger group, Paleognathae (also designated as Infraclass Eoaves, Parvclass Ratitae by Sibley and Alquist 1990). The phylogenetic relationships of Tinamiformes remain uncertain however. Morphological and molecular analyses have supported two different sister group hypotheses: either tinamous-ratites, or tinamous-Galliformes (fowl-like birds). Current debate concerns the definition of 'paleognath' and whether the paleognathous palate represents a primitive character state.

Tinamous fossils from Argentina are described from the Tertiary period, specifically the medial Miocene (Eudromia sp.) and the Pliocene (Eudromia olsoni; Nothura parvulus; Nothura padulosa). Fossils of volant paleoganthous carinate birds from the Paleocene and Eocene (Paleogene lithornithids) appear phenetically most similar to tinamiform birds.

Campbell, B., and E. Lack, editors. 1985. A Dictionary of Birds. Buteo Books, Vermillion, SD.

Carroll, R. 1988. Vertebrate Paleontology and Evolution. W.H. Freeman and Company, New York.

Caspers, G., J. Wattel, and W. de Jong. 1994. aA-Crystallin Sequences Group Tinamou with Ratites. Mol. Biol. Evol.. 11(4):711-713.

Feduccia, A. 1999. The Origin and Evolution of Birds, 2nd edition. Yale University Press New Haven.

Gill, F. B. 1995. Ornithology, 2nd edition. W.H. Freeman and Company, New York. Houde, P. and S.L. Olson. 1981. Paleognathous birds from the early Tertiary of North America. Science 214:1236-1237.

Proctor, N. and P, Lynch. 1993. Manual of Ornithology. Yale University Press, New Haven.

Sibley, C. G. & J. E. Ahlquist. 1990. Phylogeny and Classification of Birds, A Study in Molecular Evolution. Yale Univ. Press.

Contributors

Laura Howard (author), Animal Diversity Web.

Glossary

acoustic

uses sound to communicate

bilateral symmetry

having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.

chemical

uses smells or other chemicals to communicate

endothermic

animals that use metabolically generated heat to regulate body temperature independently of ambient temperature. Endothermy is a synapomorphy of the Mammalia, although it may have arisen in a (now extinct) synapsid ancestor; the fossil record does not distinguish these possibilities. Convergent in birds.

iteroparous

offspring are produced in more than one group (litters, clutches, etc.) and across multiple seasons (or other periods hospitable to reproduction). Iteroparous animals must, by definition, survive over multiple seasons (or periodic condition changes).

motile

having the capacity to move from one place to another.

oviparous

reproduction in which eggs are released by the female; development of offspring occurs outside the mother's body.

sexual

reproduction that includes combining the genetic contribution of two individuals, a male and a female

tactile

uses touch to communicate

visual

uses sight to communicate