Birds – ducks or sparrows, say – must obviously recognize their latest offspring. But if mom and dad sparrow bump into last year’s sparrowlings, now long fully grown and probably themselves procreating, will they know them?
Are there any species of bird that cultivate a kind of family relationship after their children flee the nest?
Yes, quite a few birds show kin recognition.
Some birds are even cooperative breeders , and last year’s brood may stick around to help mom and pop raise this year’s siblings.
Another, well-known bird that seems to be a cooperative breeder is the American Crow. From this page, http://birds.cornell.edu/publications/livingbird/spring98/crowsSp98.htm
[Kevin] McGowan [curator of the ornithology and mammalogy collections at Cornell University] has tagged 651 individual crows from 560 nests over the past 10 years. And he has made some basic discoveries. First, American Crows are cooperative breeders. They apparently mate for life, or until a mate becomes incapacitated, and often several generations of a single family can be found helping at a nest. Older siblings, known as helpers, may take part in building the nest, feeding the incubating female, feeding the hatchlings, and chasing away predators. “Some of these families are amazing,” says McGowan. “One marvelously successful crow family lives at St. Catherine’s Church in Ithaca–a breeding pair and up to seven generations of siblings live on or next to the home territory there.”