Tiny hummingbirds can fly a long, long way

Sometimes it’s surprising to discover how little we know about common plants or animals. Consider the ruby-throated hummingbird. If you live in the eastern half of Canada or the United States and have spotted a hummingbird hovering around a feeder in the backyard in summer, this is the bird you saw. But while scientists have documented many of the feeding and mating behaviors of the birds and that the birds migrate south to Central America and Cuba, there are still plenty of mysteries, such as whether the birds go the long way through Mexico when they migrate or whether they take a shortcut across the Gulf of Mexico.

It turns out that the tiny birds, some of which are small enough to fit in your hand, could easily take the shortcut, even though they’d get no break on the journey. Based on analyses of wing shape, body size and fat reserves, some of these tiny birds could fly more than 2,000 kilometers in the right winds. That’s more than enough to get them the 1,000 kilometers across the Gulf, researchers report March 9 in The Auk.

Theodore Zenzal Jr. and Frank Moore of the University of Southern Mississippi in Hattiesburg studied ruby-throated hummingbirds at the Bon Secour National Wildlife Refuge in Alabama, one of the birds’ stopovers on their journey south. From 2010 to 2014, they captured birds in the refuge during late summer and early fall. Birds were weighed, measured, banded and released.

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Zenzal and Moore found that older birds tended to arrive at the refuge earlier and stayed for shorter times than younger birds. They also had more fat that could fuel a long voyage, and older males had the most. Based on these fuel loads, the birds could fly for another 2,260 kilometers on average without stopping for food, the team calculates.

That was just the average, though. Some very skinny birds arrived at the refuge, and had enough fat for just a short trip of less than 20 kilometers. This may explain why some hummingbirds stuck around in the refuge for a couple of weeks — they may have needed to bulk up before taking off again. Other birds had plenty of fat, though, enough to go more than 4,000 kilometers.

Hummingbirds’ small size may actually be an advantage when it comes to long-distance flight, the researchers note. These birds are really good at taking in a lot of fuel, and being small means that they can carry a larger percentage of their body weight as fat than can larger birds.

But just because the hummingbirds may be capable of taking the shortcut across the water doesn’t mean they actually do. Weather patterns aren’t favorable for such a flight until late fall, Zenzal and Moore say. So it may make more sense, especially for juveniles, to take the long way around since there are opportunities for pit stops should they be needed.

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