When a hummingbird shows up in late fall over much of North America, it’s either a late-hatching ruby-throated hummingbird or a vagrant—a hummingbird out of its normal range. Rufous hummingbirds seem to be developing more regular movements toward the East, so what we think of as vagrants may actually be the vanguard of a small population changing its migration route.
Do our feeders encourage late hummingbirds to linger north of where they should be? Not really—after all, hummingbirds time their migration for when food is most abundant. Backyards with the richest natural food resources and best feeding stations may get more visitors than other backyards, but each hummingbird only remains as long as it needs to get its body into condition to move on until it reaches its final winter destination.
After a killing frost, when natural food becomes harder to find in northern states, hummingbirds can still get some sweet sap oozing from conifer branch tips and swarms of small insects, but concentrated sources of food do become harder to find. Those hummingbirds that hatched later in summer can die if they can’t keep their body in condition to finish migration, so naturally these late birds stick around a few days or even a week or two when they do find a good feeder. And a handful of Rufous hummingbirds have spent the entire winter in surprisingly wintry spots, and returned the following year, so we know they were healthy and not “lost.”
If you keep out your feeders for a few weeks, or even months, after the main movements of hummingbirds in your area, there is no guarantee, or even a good likelihood, that one of these stragglers will appear. But if one does pass through your area and notices your feeders, it may linger. When the probability is so low that any hummingbird will appear, it’s easy to forget about the feeder. Unfortunately, little by little the sugar water will spoil and ferment, so you’re not doing hummingbirds any favors by simply leaving feeders out unless you keep the water fresh. Fortunately, as weather gets colder, the water stays fresh longer, but even when it’s been cool, it’s best not to leave feeders out more than a week or two at the most without cleaning them and changing the water.
If you do get a hummingbird during cold weather and are home throughout the day, you can keep a second feeder filled so one can be warming up indoors to swap with the cold one as the water starts freezing. Some people keep the sugar water thawed by keeping the feeder near an incandescent light bulb, or figure out other ingenious solutions.
If a late hummingbird does appear, look at it carefully! Many late birds are vagrants—some even from the tropics! Green violetears have appeared in many states, sometimes as late as November! A calliope hummingbird from the West turned up at a feeder in Minneapolis, Minnesota, one November, and another Western species, an Anna’s hummingbird, at a feeder even further north, in Grand Marais, Minnesota, also one November.