Scientific name: Stellula calliope
While most people think of hummingbirds as being small, the Calliope Hummingbird is the smallest of all hummingbirds to breed in North America. Despite its diminutive size, some Calliope Hummingbirds migrate up to 5,500 miles each year.
Though Calliope Hummingbirds are aggressive in defense of nesting territories, they become much more submissive around other hummingbirds during fall and winter. On breeding territories, they have been known to chase a variety of songbirds, and even species as large as a Red-tailed Hawk.