For the Birds – Ruby-throated Hummingbird

Over 320 species of hummingbirds have been described. This family of birds occurs only in the New World and most species are found in Central America and South America. With a little effort, it is not hard to find a dozen species in places like southeastern Arizona. But in eastern North America, we have a single species, the Ruby-throated Hummingbird.

Ruby-throated Hummingbirds have a broad distribution occurring in the United States eastward of the 100th meridian everywhere except the southern tip of the Florida peninsula. In Canada, ruby-throats occur from the Maritime Provinces westward into Saskatchewan. No other species of hummingbird in North America has a broader geographic range.

It’s hard to think of a Maine bird whose summer arrival is more anticipated. Who is not fascinated by these little sprites? The red throat feathers (called a gorget) of a male Ruby-throated Hummingbird may seem to sparkle in the right light. Their throat feathers refract light, giving the bird an iridescence that makes the feathers seem to shimmer as the bird moves its head.

Ruby-throats winter from Mexico south to northern Panama. To migrate to eastern North America, these birds often fly non-stop over the Gulf of Mexico, a flight of 500 miles. Such a trip requires a lot of fuel and Ruby-throated Hummingbirds fatten on insects and nectars, nearly doubling their weight before the trans-Gulf flight.

The mating system of Ruby-throated Hummingbirds appears to be polygyny; one male may mate with many females. No long-lasting pair bonds are forged. A male will court a female through complicated flight displays. When a female flies into his territory, he begins with a dive display, flying U-shaped loops starting from as high as 30 feet above the female. If the female perches, he switches to very fast, side-to-side flights, with his gorget extended, within two feet of the female. If the male is acceptable as a mate, the female will cock her tail feathers to one side and lower her wings, inviting the male to mate with her. Mating lasts only about 2-3 seconds and that is the end of the male’s contribution to the offspring.

The female builds the nest by herself. The base is made of the down from dandelions and thistles and is attached to the upper side of a branch, much like a saddle over the back of a horse. The sides of the nest are made of plant down, bud scales and spider webs. The plant material is woven into the nest with the spider silk.

The eggs are usually two in number and, as you might imagine, are tiny. An average egg is half an inch long.

Incubation takes 12-14 days and the young hatch as naked, blind chicks. Feeding usually begins soon after hatching and the young fledge about 20 days after hatching.

We think of Ruby-throated Hummingbirds as depending on nectar for their sustenance. However, these birds also take spiders and insects (mosquitoes, gnats, fruit flies and small bees). Although no quantitative study has been conducted, some ornithologists have examined ruby-throat feces and estimate that 50-60% of the diet is insects.

As nectar-feeders, hummingbirds, along with many insects, serve as pollinators for a number of plants. Trumpet creeper, a forest vine, seems to be primarily pollinated by Ruby-throated Hummingbirds.

Of course, the fondness of hummingbirds for nectar makes it easy for us to attract hummingbirds to our gardens and backyards. Hummingbirds will visit many types of flowers but generally those with long, tubular flowers are most attractive. Bee balm, for instance, is a favorite of ruby-throats.

An offering of sugar water is an effective way to attract hummingbirds through artificial means. The nectar produced by hummingbird-pollinated flowers is rich in sucrose (table sugar). On the other hand, flowers that are pollinated by songbirds like Cedar Waxwings and European Starlings are rich in two other types of sugar, fructose and glucose. Experiments with Rufous Hummingbirds using solutions made from these three sugars showed a preference of the hummers for sucrose.

The best recipe for making sugar water for hummingbirds is one part sugar to four parts of water. You can heat the water to make the sugar dissolve more easily but heating the water is not necessary.

Don’t add red dye to your sugar water. The most common red food dye, Red Dye Number 40, is approved for human consumption in the U. S. but not in several European countries. We also know that substances that seem to be safe for humans may be harmful to other vertebrates. Tylenol, for example, has strong negative effects on cats. Arguments about the safety of red dyes are moot to me; most hummingbird feeders have some red on them anyway and the addition of red dye does not make the feeder more attractive. At best, red dye is useless. Why bother with it?

[First published on June 17, 2006]