Observations at a bird-feeding station in southeastern Arizona over several winters indicate that, if food is provided, it is possible for the larger native hummingbirds—Rivoli's Hummingbird (Eugenes fulgens) and Blue-throated Mountain-gem (Lampornis clemenciae)—to survive periods of subfreezing temperatures, even while spending considerable time and energy defending artificial nectar feeders.
Prior to the winter of 1973–74, there were few records of these two species wintering in southern Arizona, although Christmas Bird Counts at Ramsey Canyon in the Huachuca Mountains included one or both species from 1969 through 1971. In 1973–74, a female Blue-throat spent the winter near Portal, in the Chiricahua Mountains, visiting several feeding stations. That was a relatively mild winter, with temperatures rarely going below freezing. Since that year, we have had one or two individuals of either or both species winter over each year, feeding on an artificial nectar mixture of 5 parts water to 1 part sugar. On cold nights, we brought nectar feeders indoors to prevent freezing, returning them to outdoor hangers at daybreak.