Where do they come from, and where do they go?
In the case of western hummingbirds wintering in the East, we really don't know. That's part of what makes this research so fascinating.
In the case of rufous hummingbirds, the most common western species in the East, we assume they are coming from the species' normal breeding range, which stretches from northern California and the northern Rockies into southcentral Alaska. But whether the individuals wandering East come from a specific region within that vast area, or are drawn from the entire range of the species, is still unknown.
There have been some remarkable discoveries, thanks to banding. A rufous hummingbird that wintered in Richmond, Virginia was recaptured the following summer in Red Lodge, Montana, before returning to the same backyard in Virginia.
Another rufous hummingbird, banded in Tallahassee, Florida, in January 2010, was recaptured in July 2010 in Chenega Bay, Alaska - a straight-line distance of more than 3,500 miles, and the longest movement ever recorded for any hummingbird species.
Other hummingbirds regularly recorded in the East include Allen's hummingbird, which breeds along the southern California coast; Anna's hummingbird, which lives year-round along the Pacific Coast and winters as far north as British Columbia; the calliope hummingbird, which breeds in the northern Rockies; the black-chinned hummingbird of the Great Plains and Rockies; and the broad-tailed hummingbird of the Rockies and western Plains.
Once the hummingbird is banded, the band remains on its leg for life, so that if it is encountered again, its movement, life span and other critical information can be learned. Despite its small size, the number code on the band can sometimes be read with binoculars while the bird is perched at a feeder.