"Broken Wing" display in female Killdeer (Charadrius vociferus)

     When a predator approaches her nest, the mother killdeer will perform an elaborate display suggesting one or both wings are broken, and may emit a distress cry. The mother leads the predator away from the nest, and the predator follows. At an appropriate distance, the killdeer makes a miraculous "recovery" and flies off.

    Such self-sacrificing behavior should evolve by kin selection, if sacrifice of the mother increases the expectation that two or more offspring will survive.