People who feed hummingbirds often wonder if keeping feeders up once the migration of ruby-throated hummers starts will encourage them to stick around, possibly putting them at risk.
According to the Cornell Lab of Ornithology’s 2009 BirdNotes newsletter (available at allaboutbirds.org), hummingbirds have a strong instinct to migrate and, even if full feeders are available, will leave in response to decreasing daylight and “other environmental cues.”
Hummingbirds actually migrate south when food is most abundant. “When the bird is fat enough, it migrates,” as the website Hummingbirds.net puts it. The slower-burning protein and fat that comes from eating insects is more important in sustaining them in their journey south. “Hummingbirds are carnivores,” the site adds. “Nectar is just the fuel to power their fly-catching activity.”
Leaving feeders out will not only help stragglers but may attract strays from other species, such as rufous hummingbirds, which are hardier and have extended their winter range to here and even further north. Cornell Lab’s newsletter suggests that, once temperatures drop below 28 degrees, it’s a good idea to bring the feeders in at night so the sugar solution in them won’t freeze.
According to Hummingbirds.net, the birds are hardier than they look and can survive sub-freezing temperatures and even blizzards by going into torpor, a sleep-like state that saves energy. However, ruby-throated, the only hummer that breeds here, don’t do well below the mid-20s. They’re less likely to go into torpor than the rufous and therefore are more at risk of freezing to death.
When do hummers leave? Mature males may leave as early as July, but peak migration for the species is late August through early September. By mid-September, the ruby-throated at feeders are migrating through from farther north, and are not the same individuals seen in the summer.
Hummingbirds can fly about 25 miles per hour in a straight line under good weather conditions. Their migration south can cover more than 3,000 miles depending on where the hummers are coming from and how far south they’ll go before they stop for the winter. While most go to Central America, crossing the 500 miles of the Gulf of Mexico in one shot or skirting around the coast, a few – particularly those that breed further north than Virginia – find the Gulf states to their liking.