Tinamous are birds restricted to the forests and grasslands of Central and South. America, where they are thought to have had their origins. The superficial resemblance of certain species of this ground-living group to game birds, especially the guinea fowl (family Numidia), is no indication of their true relationship, for a recent analysis of their egg-white proteins, DNA, and bone structure indicates that they are more closely related to the rheas. Indeed, it has been suggested that ancient tinamou relatives actually gave rise to all ratites, even though the breastbone (sternum) possesses a well-developed keel, which the ratites lack.
To the casual observer, tinamous outwardly recall the guinea fowl in their proportions and carriage but differ in that the bill is slender, elongated, and slightly decurved. Further, the rear of the body appears arched owing to the great development of the rump feathers which normally obscure the short tail. The legs are thick and powerful and possess three forward-pointing toes and one rear toe. The latter is reduced and elevated, or even absent income species. Although the legs are perfectly adapted for running, the birds soon become tired when chased and often stumble. Their flying ability also leaves much to be desired, for though they have well-developed flight muscles, their flight is clumsy and they often collide with obstacles, which sometimes results in injury or death.
Because of their limited running and fly-in capabilities, tinamous rely on their pro-tektite coloration to avoid detection. They remain motionless with heads extended, attempting to blend in with the vegetation, and will creep away from danger using all available cover. Species living in more open areas are known to hide in holes in the ground. At all times they only break cover, or take to the wing, at the last possible moment. For these reasons the tinamous are not the easiest of birds to see in their natural environment, their presence is indicated only by their flute-like, whistling calls, which can be uttered day or night.
Some crop and stomach contents have been analyzed, and indicate that they feed mainly upon fruits, seeds, and other vegetable matter such as roots and buds. Insects and other small animals may also be taken, especially by species of Nothoprocta, while the Red-winged tinamou may also eat mice. As in ratites, the sexual roles of the tinamous are largely reversed, with the male taking care of the eggs and young, While the female is the most aggressive and the main participant in the courtship display. Polygamy is common with the tinamous. It is common for one or more females to lay eggs in one nest, and occasionally a hen will deposit her eggs in different nests, which are being looked after by different males.
Detailed accounts of nesting are very hard to come by. It is almost certain that the species that live in tropical forests nest in many months of the year, while others may have their egg-laying season governed by rainfall and other climatic factors. What can be said with certainty is that all are ground nesters and either lay their eggs directly on the ground, between roots in a shallow scrape or construct a nest of grass and sticks. Clutches are said to consist of 1-12 eggs, though the latter figure may be the result of two females using one nest. The eggs are relatively large and renowned for their hard, porcelain-like gloss and vivid clear coloring. On hatching, the chicks are downy and buffing in color with darker stripes and mottles. They are very well developed, being capable of running soon after hatching; most species are able to fly to some degree before they are half-grown.
During the nesting period, males often become so tame that they can be picked up off the nest. In the Tatiana tinamou thecock will pretend to be lame in order to dies-tract the intruder away from the nest, while other species may cover their eggs with leaves as in timorous species, or with feathers as in Nothoprocta species. Throughout their range, tinamous are sought after as food. This is because their meat, although having a strange trans-lucent appearance, is very tender and full of flavor.
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