I was watching some sparrows while I was waiting for my bus this morning. I saw two sparrows interacting in a way I had seen them do last week. One would get a crumb of food. The other one, whose markings were more subtle than those on the other sparrows, would rapidly flutter its wings very close to its body and chirp. The other sparrow would feed it by putting the crumb in its mouth. I suspect that the former was a juvenile, and that it’s fairly recently out of the nest. But it was about the same size as the latter sparrow, and there were plenty of crumbs available for the taking. Why did it insist upon being fed?
Because even birds still want mommy to take care of them once in a while.
The parents continue to respond to the feeding-stimulus behavior of the offspring for longer than just when they’re in the nest. I’m not sure what finally brings this to a stop. (Boredom?) In some species, the newly adult birds will finally be driven out of their parents’ territory, but of course this applies less to flocking birds like sparrows and starlings and pigeons.
In many species of birds, the young are just about the size of the adults when they leave the nest. Also in many species, the young will rely on the parents to be fed for several weeks or even months after leaving the nest. (In Harpy Eagles, it can be over a year.) The young follow the adults around begging, and will be fed for a time as they gradually learn to forage on their own.
I’ve observed this kind of behaviour in starlings.
The fledglings are of a similar size to the adult birds but distinguishable from them in sporting much paler colours. It’s my habit to spread several piles of raisins on a wall in the garden and see what happens. I’ve noted that a fledgling will often arrive first and land in a pile of said raisins, waiting for a parent to come along and feed it. Where several young are waiting to be fed by the same parent, one or two of them will investigate the raisins and, eventually, they all pick up the idea that it’s definitely food and that it’s OK to help themselves.
Ditto on what has been said. In addition, when you start messing around with the situation you can get some interesting behaviour. When I have hand fed parrots, I have delayed weaning intentionally in order to further reinforce bonding. Many of those birds will revert to “baby behaviour” when they see a hand feeding syringe at some later date, even years later.