They like noise and activity. A starling's idea of fun is being surrounded by a den of excited cub scouts. A starling is also content on its own, so it will not pine away if you go on vacation for a few days. Someone who works in wildlife rehabilitation reminded us that it is legal to kidnap a starling in the United States because it is a non-native species. If you find an injured or lost native bird, you should contact your local zoo, aviary, Audobon Society representative, Fish and Wildlife service, or other expert for advice.
Starlings drive out native birds, most notably the purple martin.
You should only adopt a starling if you intend to keep it. If you raise one, and release it, you are introducing a non-native bird into the environment. If you live outside of the United States you should check local regulations before taking any bird from the wild. Having warned you . . . A good time to catch a starling is when it is just learning to fly, but hasn't left the nest.