 the rails, or rallidae, are a large cosmopolitan family of small- to medium-sized birds. the family exhibits considerable diversity and also includes the crakes, coots, and gallinules. many species are associated with wetlands, although the family is found in every terrestrial habitat except dry deserts, polar regions, and alpine areas above the snow line. members of the rallidae occur on every continent except antarctica. there are numerous island species. the most common rail habitats are marshland or dense forest. they are especially fond of dense vegetation.horsfall & robinson (2003): pp.&nbsp;206â207 ==morphology==  the rails are a fairly homogeneous family of small to medium sized ground living birds. they vary in length from 12&nbsp;cm to 63&nbsp;cm and in weight from 20 g to 3000 g. some species have long necks and in many cases are laterally compressed. the bill is the most variable feature within the family: in some species it is longer than the head (like the clapper rail of the americas), in others it may be short and wide (as in the coots), or massive (as in the purple gallinules).horsfall & robinson (2003): p. 208 a few coots and gallinules have a frontal shield, which is a fleshy rearward extension of the upper bill. the most complex frontal shield is found in the horned coot.horsfall & robinson (2003): p. 210 rails exhibit very little sexual dimorphism in either plumage or size. ===flight and flightlessness=== the wings of all rails are short and rounded. the flight of those rallidae able to fly, while not powerful, can be sustained for long periods of time, and many species migrate annually. the weakness of their flight, however, means they are easily blown off course and thus are common vagrants, a characteristic that has led them to colonize many isolated oceanic islands. furthermore, these birds often prefer to run rathe
Bird_families Rails Rallidae