Duolingo, You should consider 'a/the/none' and 'singular/plural' distinction/flexiblity in translation more carefully.
"A light chicken eats more." and "Light chickens eat more." are both appropriate here, and "The light chicken eats more" and "The light chickens eat more." can be fine in some contexts.
A "light"chicken is a common term in the poultry industry. Chickens "go light" i.e. loose weight when they are ill. If one picks up a chicken of the same age as the rest of the flock and it is "light" regarding its weight, the farmer, etc. knows that it is a sick bird even if it shows no other signs of illness.
This is an instance where the dynamic translation ability of the organic mind out shines AI. Humans can easily make the following connections light = light weight = not heavy = skinny = scrawny = small = slim = this chicken eats a lot of food but doesn't put on much weight = is this chicken bulemic or does it have a high rate of metabolism = either way, this chicken is strictly pet material.