The yellow-legged buttonquail (Turnix tanki) is a buttonquail, one of a small family of birds which resemble, but are unrelated to, the true quails. This family is peculiar in that the females are larger and more colourful than the males and are polyandrous.
The yellow-legged buttonquail is a small quail growing to a length of 15 to 18 cm, the females being slightly larger and more brightly coloured than the males. The weight is 36 to 43 g for the subspecies Turnix t. tanki, and 35 to 78 g for the male Turnix t. blanfordii, while the female of this subspecies is 93 to 113 g. The tail is short and the wings have rounded ends.
The adult male has a black crown with a buff margin, and sometimes a buff central streak. The front and side of the head are buff, the individual feathers having black tips. The throat is pale buff, darkening to reddish-buff at the edges and on the breast, and paling again on the belly, becoming white at the under tail coverts. The sides of the breast are scattered with round black spots. The nape and upper parts of the body and tail are greyish-brown, with reddish and dark brown vermiculations and spotting. The main wing feathers are blackish-brown with buff margins, and the wing coverts are buff with dark spots. The beak is dull yellow, the irises whitish, and the legs and feet deep yellow.
The adult female differs from the male in being a richer colour and in having a broad, reddish-brown collar round the back of the neck. The spots and vermiculations on the back and tail are not so dark, the beak and legs are brighter yellow, and the irises are creamy white or yellowish-brown. In non-breeding plumage, the rufous collar of the female becomes mixed with grey and the other plumage also become greyer. The juvenile is similar to the male in appearance but has dingier plumage, a less vivid breast colour and more fine speckling.