Male owl Pigwidgeon is an overeager, overconfident, hyperactive owl, especially compared to the more stately delivery owls. Pigwidgeon was a gift from Sirius Black to Ron, to replace his rat, Scabbers. Pigwidgeon was named by Ron's sister, Ginny.
There have been various theories as to what kind of owl Pigwidgeon is, but J.K. Rowling has confirmed (on her website) that he is a Scops Owl, a tiny breed of owl with earlike feathers that she had previously mentioned in an earlier book.