Besides Robins, are there any other birds that will feed the young of other birds?

Answer 1

There are many birds that are "nest parasites" -- they lay their eggs in the nests of other birds and leave the other bird to sit on the eggs and rear their young. Most common examples are the brown headed cowbird in the US and the cuckoo in Europe.

It is funny and sad to see a tiny song sparrow mother trying to keep up with the appetite of her huge cowbird "baby"

Answer 2

Brown cow birds and cuckoo's lay their eggs in other birds nests and have their young raised by the foster parents. There are several species that both bird parasitise.

http://en.wikipedia.org/wiki/Brood_parasite

Answer 3

Yes. Example: brown-headed cowbird. This bird is what as known as a nest egg dumper. The female lays its own egg in the nest of other birds. The other species incubates, hatches, feeds and raises the baby cowbird as if it was one of its own.

http://www.birds.cornell.edu/BOW/BNHCOW/