Laura Erickson's For the Birds

Hummingbirds

(Recording of a Ruby-throated Hummingbird)

A couple of weeks ago I got a lovely illustrated letter from a little girl named Eva Treuer asking me to please talk about hummingbirds on my program. Of all the birds, the hummingbirds are definitely the tiniest and perhaps the most beautiful, with their intense iridescent colors. Every one of the over 300 species of these avian jewels is found only in the Americas, though on our two continents they can be found anywhere from Alaska to the southern tip of South America, wherever flowers bloom. European settlers and explorers were fascinated by this exotic family–Audubon called the hummingbird a “glittering fragment of the rainbow.”

Hummingbirds are uniquely adapted to eating the nectar of flowers. The bright throats of the males, called gorgets, give a bit of an indication of the colors of flowers each species is especially attracted to, and the length and shape of their beaks often indicates the shape of the flowers they are adapted to.

Although the Giant Hummingbird of South America is over 8 inches long, many of the birds in this family are at the lower limit of size for warm-blooded animals. These atom-sized birds have atomic power as well–they feed at over 1500 flowers every day, their wings beat 75 times every second when flying straight ahead, and their hearts pump blood through their thread-like blood vessels at a rate of at least 1260 beats per minute. Crawford H. Greenwalt wrote, “For its size a hummingbird outperforms any warm-blooded animal. While hovering, it has an energy output per unit of weight about ten times that of a man running nine miles an hour. If a 170-pound man led the equivalent of a hummingbird’s life, he would burn up 155,000 calories a day and evaporate about 100 pounds of perspiration an hour. If his water supply ran out, his skin temperature would soar above the melting point of lead, and he would probably ignite. There is much to be said for our relatively sedentary existence.”

In spite of their small size and the intensity of their lives, hummingbirds can live surprisingly long lives. There are many records of individual hummers living over 8 years, and the oldest known wild one, a Broad-tailed Hummingbird, was over 11 years old when banders recaptured and released it. They are extraordinarily pugnacious–I’ve watched males chase down and harass hawks and even a Bald Eagle. Because of their speed and maneuverability in flight, they are sometimes said to have no enemies, but in reality there are many records of them being killed and eaten by small falcons, accipiters, flycatchers, and orioles, and they have also been taken by frogs, fish, and tropical spiders.

By now our own northland hummingbirds have crossed the Gulf of Mexico and are in the central United States–about the latitude of Arkansas and northern Texas. The earliest one has ever arrived in the northern half of Minnesota was April 30, but most of them don’t get up here until mid or even late May. When they reach the Northland, the weather can be cold and miserable, especially near the shores of Lake Superior, at a time when they are already exhausted and thin after their long journey from Central America. When a cold-front hits after they arrive, hummingbird feeders probably save the lives of many of these tiny treasures.

(Recording of a Ruby-throated Hummingbird)

This is Laura Erickson, and this program has been “For the Birds.”