eat like a bird/horse, to

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.