Our library has four tall Savannah Holly trees flanking the Park Avenue entrance. I enjoy observing these trees through the year. When they flower in late spring, a cloud of small bees comes to pollinate them. Now, when their berries are red, but not yet full and ripe, they are visited by a great number of wasps. It is hard to see what it is that attracts them. A couple of years ago, reference librarian that I am, I "looked it up".
Holly trees are prey to flies whose larvae are "leaf miners", feeding on the inner tissue of the leaves. The wasps are parasitic, laying their own eggs near the fly larvae to feed upon them in turn, thus doing the trees a service.
In the winter, flocks of cedar waxwings will come to eat the holly berries. Always one or two will dash themselves, sometimes to death, against the library's windows. In Woodville, with the bookmobile, I once saw a flock of these birds pick a small holly tree clean in minutes.