Take a look at this range map of North American hummingbird breeding ranges. Isn’t it interesting that the west, in particular the southwest, is full of many species while the east is covered by just one species? And how about that large tract in the middle with no hummingbirds? Let us know in the comments why you think this may be. We don’t know but we’ll look for any research or theories and update this post with them at the end of the month.
Mouse over any hummingbird to see its name and range
Source: Birds of North America Online
By Project FeederWatch Project Leader Dr. Emma Greig
You may not realize it, but hummingbirds are a special family of birds that only occur in North and South America. The largest species diversity of hummingbirds occurs in South America, and as you move north or south, species diversity becomes lower. What does this mean for our North American hummingbirds? It means that most species live in the southwest US, and only a few species breed in the north or southeast: in the northeast, it is only Ruby-throated Hummingbirds!
So why is southeastern Arizona a hub of hummingbird diversity, and not other southwestern locations such as south Texas? It probably has a lot to do with the plants (which hummingbird need for both nectar and insects), which in turn is effected by elevation and rainfall. Both high elevation and (relatively) high rainfall tend to be associated with higher species abundance of hummingbirds, which gives Arizona a leg up in comparison to places such as Texas and Florida.
So what is the take home message? Hummingbird species diversity is probably explained by two thing: 1) by a gradual geographic spread of species away from the rainforests of South America, and 2) by the availability of suitable habitat that can support the coexistence of many hummingbird species.
REFERENCE: Wethington, S M., G. C. West, B A. Carlson. Hummingbird conservation: discovering diversity patterns in southwest USA. (2005) USDA Forest Service Proceedings RMRS-P36