 The rails are a bird family comprising nearly 150 species . Although origins of the group are lost in antiquity , the largest number of species and least specialised forms are found in the Old World , suggesting this family originated there . The taxonomy of the small crakes is complicated , but the closest relative of the corn crake is the African crake , C. <unk> , which has sometimes been given its own genus , <unk> , but is now more usually placed in Crex . Both species are short @-@ billed brown birds with a preference for grassland rather than wetland habitats typical of rails . <unk> crakes , particularly the ash @-@ throated crake ( <unk> <unk> ) are near relatives of the Crex genus . 
