There are an estimated 300 hummingbird species worldwide and some new ones are discovered every few years. Out of these hundreds of varieties, fewer than two dozen can be seen as far north as the United States and Canada. Out of these, only a handful are year-round residents of North America. Knowing what species are in your area can help you plan the best planting schedule for those hummingbirds. To learn more about hummingbirds, you might want to buy a field guide specific to hummingbirds.