Guam rails are small, flightless but fast-running birds with narrow bodies. They have chocolate-brown heads and necks, and a plain gray stripe just above the eye that draws attention to their medium-length gray bills. Their lower necks and upper breasts are also gray, and they have white stripes, called bars, beneath a mantel of light brown shading to buff on the neck. The Guam rail's short wings are dark with brown spots and barred with white. Its lower breast, abdomen, under tail coverts and tail are black with white bars. It has strong, medium-length legs and long toes that help it walk over grasses and soft marsh mud. Guam rails are small birds that grow to lengths of about 11 inches (28 centimeters) and weigh 7 to 12 ounces (200 to 350 grams). Females are slightly smaller than males, but their plumage is the same. The median life expectancy for female Guam rails is 5.7 years. For males, it is 9.5 years.