We put out orange halves when it is cooler. When it gets hot the things are covered in flies, nothing else. We've seen several butterflies, and birds. The Red-bellied woodpeckers really chow on the oranges.
We tried bananas last year for butterflies, but it was too hot... flies. But another year, the Red-headed woodpeckers really liked it. I felt kind of bad because their bills were a mess, so didn't put any more out that year. I am sure it cleaned off, but at the time I kind of freaked wondering if that would have in some way made life miserable for them.
We've done apple and melon leftovers. A lot of flies, too, but Painted Ladies got to it, too.