Scientific Name: Archilochus colubris
Common Name: Ruby-throated Hummingbird
(Information for this species page was gathered in part by Ms. Mallorie Bonitz for an assignment in Biol220W, Spring semester 2006)
The ruby-throated hummingbird (Archilochus colubris) is the most common hummingbird species in the eastern half of the United States. Its range extends from the eastern seaboard to west of the Mississippi River, north into southern Canada, and south into Mexico. It is a small (3 or 4 inches long) bird with a wing span equal to its length. It weighs between 2 and 6 grams (0.07 to 0.21 ounces). Both males and females have metallic green backs, wings, and tails with a dull-white chest that darkens toward the belly. Males are distinguished from females by their bright red throats (female throats are dull-white). Also, the females are larger than the males and have longer bills.
Both male and female hummingbirds have long, needle-like bills and are able to move their wings in a rapid blur (55 beats per second!) when they fly. These rapid wing movements along with anatomical adaptations that allow rotation of the angles of their shoulder joints enable these birds to hover and fly both forward and backward.
Ruby-throated hummingbirds in spite of their small size are long distance migrators. They overwinter in tropical deciduous and tropical dry forests (and citrus groves and secondary scrublands) primarily throughout southern Mexico and Central America and rarely in the Gulf Coast states. They breed in the summer all across their previously described, broad, North American range. The flights in between these locales are done in nocturnal stages that follow the blooming of the spring flowers from south to north and the seasonal senescence of plants from north to south. Males migrate south in July while females and fledges go south sometimes as late as the onset of frosts in October.
Ruby-throated hummingbirds are nectar feeders. They move quickly from bloom to bloom sipping up the tiny volumes of sugar. Over 150 North American plants have flowers that are long and deep and ideally designed to encourage feeding (and subsequent pollination) by hummingbirds. In addition to these plant nectars, though, ruby-throated hummingbirds hunt and consume large numbers of insects (including ants, gnats, fruit flies, mosquitoes, maggots, and caterpillars) and spiders. They frequently hunt these prey species by perching on tree branches and visually searching for and swooping after passing, flying insects (a behavior referred to as “hawking” or “gnatting”). Large numbers of insects may be captured in a single hawking session. Ruby-throated hummingbirds also actively forage for insects up and down tree branches. Some observers, emphasizing the importance of insects in the diet of these birds, refer to hummingbirds in general as “nectar powered flycatchers.” Hummingbirds also drink tree sap that oozes from bark wounds (often from holes drilled by woodpeckers and sapsuckers). They also readily feed at sugar-water feeders (a topic that will be discussed more fully at the end of this paper).
Both male and female ruby-throats stake out territories. These individual territories are between several hundred and several thousand square yards. Selection criteria for these territories, though, differ between the genders: females look for reliable food sources and good nesting sites, males look for areas in which females are abundant. Ruby-throats do not form pair bonds, and males, after short, energetic courtships and matings, leave the females to build their nests and rear their young alone. Males will mate with as many females as possible and will attempt to maintain their territories against other males via aggressive displays and vocalizations and, rarely, physical confrontations.
Nests and Reproduction
Nesting sites are typically located in deciduous forests that have widely scattered trees. Many suburban yards fit this description very well. Nests are often built on downward slanting limbs frequently near a stream or other water source. The nests are tiny and are constructed of thistle seed, dandelion down, hair, feathers, and finely stripped pieces of tree bark. Spider webbing is used to glue these soft materials together. Lichens and other green materials are frequently added to the outside of the nest for camouflage. Nests can be used for more than one season, but yearly repairs and reconstructions are often required.
The female lays two, white, “pea-sized” eggs about 3 days apart and incubates them almost continuously (80% of daytime hours) for 12 to 16 days. Nestlings are warmed and fed (a regurgitated mix of nectar and insects) by the female for the next 2 to 4 weeks. The nestlings tend to fledge together and will continue to be fed by the female for about 10 more days. If a female nests early enough in the season, she may have time to have a second clutch. This “double clutching” is more common in the southern states than in the north.
Hummingbird feeders are an increasingly popular addition to many bird feeding stations. If these feeders are filled with an appropriate sugar solution, and if they are kept clean and free of bacteria, they can be an excellent way to both augment the energy budgets of a hummingbird population and also bring these birds in close to be observed and appreciated. Hummingbirds find feeders by accident, by curiosity, or by observing other hummingbirds. Elaborate design features (like fake flower blossoms) do not seem to make one feeder more attractive to hummingbirds than the next. A perch for the hummingbirds to rest on while feeding, however, although not representative of the way the birds address themselves to flowers, makes energetic sense for their potentially long durational feeding visits.
Sugar water for the feeders can be made from cane sugar (sucrose) and tap or well water (to provide trace minerals needed by the birds). Honey should never be used in hummingbird feeders because in dilute solutions it rapidly ferments and can be toxic to the birds. Food colorings (even the very popular red dye!) should be avoided, too. There is some evidence that these dyes can cause tumors in hummingbirds. Jell-O, brown sugar, added fruits, and fruit juices should also be avoided. The hummingbirds use nectar (and the feeder’s sugar water) as fuel to propel their insectivorous life style. Don’t confuse what seems healthy for a human with what is healthy (and natural) for a hummingbird!
There are many formulae for hummingbird food. Here is a very simple one: 1 cup white cane sugar, 4 cups tap water. Mix until sugar dissolves (it is not necessary to boil the solution). The sugar solution can be stored in the refrigerator for up to two weeks.
Procedure for feeding and feeder maintenance: every time you fill the feeder, rinse thoroughly with hot water (do not use soap). Inspect feeder for mold. If mold is present (or at least once a month) you should clean the feeder with a dilute bleach solution (1/2 cup bleach in 1 gallon of water) or a full strength vinegar solution. Rinse very well with water and let dry before refilling. Feeders can be left up in late summer and early fall until no more hummingbirds are seen (the presence of feeders does not delay migration!).