Without question the most deplorable event in the history of American ornithology was the introduction of the English Sparrow.  —W. L. Dawson, The Birds of Ohio, 1903

Somebody asked me why I refer to the House Sparrow as an introduced species.  The House Sparrow (Passer domesticus) occurs naturally in most of Europe and Asia, although it was originally brought to those lands by the ancient Romans.  It is not a native species to North America.  Instead, the House Sparrow was intentionally introduced to much of North America by the British in 1850.  Some say that the House Sparrow was brought over as natural pest control while others believe that the Brits just wanted a familiar feathered friend in the New World.  Whatever the reason, the House Sparrow spread rapidly from New York City.  By the mid-20th century, it had claimed most of the United States and Canada as its home.

The House Sparrow is not the only prominent non-native species around town.  The Rock Dove, European Starling, and Mute Swan are all introduced species that have dominated the locals.  You never thought of pigeons as exotic, did you?