Button quail (Coturnix chinensis)—also known as Chinese painted quail or blue-breasted quail—are native to China, India, Taiwan and other areas in Asia, as well as Madagascar and parts of Australia. Since these small birds are as cute as a button, they've become popular as pets. You can tell males and females apart in several ways.
Painted That Way
One of the most obvious differences between male and female button quail is their coloration. Wild-type males are dark brown, with slate-blue chests, rusty red bellies, black eye stripes and black patches surrounded by white bands on their throats. Females lack these more intricate markings and are usually brown all over, with rust-red abdomens and chests. However, several different color mutations have been bred in captive birds, so it might not be as easy to tell males from females. Even in these cases, females tend to have duller coloration.
Size Isn't Everything
When it comes to size, button quail are unusual, as females are larger than males. On average, females of the species measure 5 inches long, whereas males are closer to 4 1/2 inches in length. Females also tend to have slightly longer tail feathers. These quail can range in weight from roughly 1 to 1 1/2 ounces, with females on the higher end of the spectrum and males on the lower.
It's easiest to tell the difference between male and female button quail when breeding season comes around. Males will display to females they wish to mate with by puffing out their chests, lowering their wings and running about. Females don't engage in this kind of behavior. If you spot button quail making nests, incubating eggs or raising chicks, they're definitely females, as males have no parental involvement. Males of the species are also more likely to be aggressive toward one another. You may also see them offering small pieces of food to females while emitting peeping noises. Females rarely do this for males.
You have a few other ways of telling male and female button quail apart. If you can get close enough, take a look at their vents: females—especially those who've laid eggs—should have larger vents than males. Females of the species may also look slightly larger around the hips. You can identify male button quail by their calls, which sound like "pee pee pew."