Wide Open

Every spring, ornithologists observe the same phenomenon in nesting songbirds. When an eastern bluebird parent returns to the nest with a caterpillar in its beak, the hatchlings don't shrink back. They don't wait to be called. Blind, featherless, and utterly dependent, they crane their necks upward and stretch their mouths as wide as they possibly can. Scientists call this the "gape response," and research shows something fascinating: the chick with the widest, most vigorous gape gets fed first.…