Common Starling or Sturnus vulgaris
Starlings, which were brought to the U.S. from Europe in the late 1800s, are a highly aggressive species that can take over nests of native birds, destroying eggs and killing nestlings (Dolin and Mannan 2009). They find saguaro cactus cavity nests particularly appealing to the detriment of native species like the Gila woodpecker.

The common starling or European starling (Sturnus vulgaris), also known simply as the starling in the British Isles, is a medium-sized passerine bird in the starling family, Sturnidae. It is about 20 cm (8 in) long and has glossy black plumage with a metallic sheen, which is speckled with white at some times of year.