Sixteen subspecies of this most familiar of the grassland sparrows are recognized, each slightly different in coloration and song. The formation of many subspecies usually indicates that the birds are faithful to their native area. One large and pale form that breeds at Sable Island, Nova Scotia, was until recently considered a separate species, the "Ipswich Sparrow." Savannah Sparrows are able runners; once discovered, they drop into the grass and dart away. In the fall they migrate southward in huge numbers and may then be found almost anywhere, even in city parks.