eat like a bird/horse, to

To not eat very much. The phrase evokes the image of a pecking bird. Don't worry about making extra food for Kim, she eats like a bird.

To eat large quantities of food. Kim is staying for dinner, and she eats like a horse, so you better make some extra food.

Fig. to eat only small amounts of food; to peck at one's food. Jane is very slim because she eats like a bird. Bill is trying to lose weight by eating like a bird.

Fig. to eat large amounts of food. No wonder he's so fat. He eats like a horse. John works like a horse and eats like a horse, so he never gets fat.

Eat very little, as in Jan is very thin-she eats like a bird. This simile alludes to the mistaken impression that birds don't eat much (they actually do, relative to their size), and dates from the first half of the 1900s. An antonym is eat like a horse, dating from the early 1700s, and alluding to the tendency of horses to eat whatever food is available. For example, I never have enough food for Ellen-she eats like a horse!

If you eat like a bird, you eat very little. She ate like a bird, refused a glass of wine, and was only interested in talking about her work. My younger daughter eats like a bird.

If someone eats like a horse, they eat a lot because they have a large appetite. When Kelly is on medication, he eats like a horse.

To eat very little/very much. The first comes from the misconception that birds don’t eat much, and indeed, they seem to peck away at tiny bits of seed and other food. In fact, however, they do eat quite a bit relative to their size, some birds actually consuming their weight in food each day. In print the term appeared only in the twentieth century, as in Barnaby Ross’s The Tragedy of X: Drury Lane’s Mystery (1930): “She ate like a bird, slept little.” To “eat like a horse,” based on the idea that horses eat a great deal, dates from the eighteenth century.