Complex sentence: The most important prey species are small mammals and birds, especially the Ruffed Grouse, snowshoe hare, and red squirrel in North America, pigeons and doves, and woodpeckers, jays and passerines (prey species vary by region).
Split into simpler sentences: The most important prey species are small mammals and birds, especially the Ruffed Grouse, snowshoe hare, and red squirrel in North America. Prey species may be quite diverse, including pigeons and doves, and woodpeckers, jays and passerines (species vary by region).