"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 sudden "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.