Carol I took this info off of the Arizona-Sonora Desert Museum site to answer your question.
There are well over three hundred species of hummingbirds, all native to the Americas. The vast majority, not surprisingly, are found in the tropics, where flowers abound year-round. Only a handful of species reach the United States; southern Arizona hosts more than a dozen of those. Costa’s Hummingbird is the only true desert hummer here, but several others live along the desert’s edges. Black-chinned and Broad-billed Hummingbirds nest in streamside woods in summer, while Anna’s Hummingbird, a recent invader from California, nests in the same areas (and in residential neighborhoods) in winter. Our region hosts the greatest variety of hummers in late summer, when several species are on their way south. Rufous Hummingbirds, southbound from nesting grounds in the northwest U.S., may appear in the Sonoran Desert by July, along with lesser numbers of other species, to joust for space around the blooms that follow the summer rains.
