Ruby-throated Hummingbird

Ruby-throated Hummingbird
The hummingbirds of North America share a medium-length bill for generalized feeding on a variety of plants, unlike some South American species that have evolved to become a single plant’s sole pollinator, developing elongated or curved bills that match the shape of a specific flower. It is believed that the evolution of as many as 19 species of plants in the eastern United States has been influenced by hummingbird pollination. Bird-pollinated flowers are usually brightly colored (especially red) and radially symmetric, have horizontal or hanging placement on the plant, and often have recurved petals. Ruby-throated Hummingbirds breed throughout eastern North America and feed on the nectar of more than 30 plants. In some parts of the range, they seem to be particularly adapted to certain key plants, and the Ruby-throat's nesting distribution may be locally determined by the occurrence of these plants. Examples are bee balm in New York and impatiens in North Dakota.
Ruby-throated Hummingbird Range Map

In addition to nectar, small insects are an important part of the Ruby-throated Hummingbird's diet. Small flies, bees, wasps, and spiders are taken at flowers, but they are also gleaned from bark or found beside sapsucker's sap wells. At times, these hummingbirds feed by flycatching in clouds of gnats.

Ruby-throated Hummingbirds have one of the longest migration paths of any hummingbird. Early researchers concluded that migrants could not cross the Gulf of Mexico because the energy demands of a 500-mile journey were beyond the capabilities of such a small bird. Later, it was believed that Ruby-throated Hummingbirds put on enough fat before migration to meet the demands of such a flight. It is now believed that at least some of the population makes the flight from Florida to Yucatan. The majority however, migrates around the Gulf through Texas and northern Mexico to winter in Central America as far south as Panama.

The northward migration of Ruby-throated Hummingbirds in spring appears to coincide with the flowering of certain key plants along their route, including red buckeye, clove currant and columbine. At the northern limits of their range, in Saskatchewan, they have been seen visiting sap wells drilled by sapsuckers before most plants have begun flowering.
Spring 2003 Migration of Ruby-throated Hummingbirds

During spring, males return north before the females and immediately establish foraging territories. Females construct the tiny nest out of leafy material and scales held together with silk from spider webs or tent caterpillar nests and decorated with lichens. Nests, which are placed on downward sloping limbs that are overhung by other branches, are sometimes reused. Once the female has constructed the nest, she is ready to engage in courtship with a male. Males perform a back-and-forth display flight arcing wide over the female. Sometimes the pair engages in a mutual up-and-down flight. After a few days, the pair dissolves and the female incubates the two bean-sized eggs and feeds the hatchlings by herself. Young hummingbirds are born naked and blind, but after about three weeks, they are ready to leave the nest.

In the eastern two-thirds of the country where this is the only hummingbird species likely to be encountered, the Ruby-throated Hummingbird might be mistaken for one of the large hawk moths that also hovers before flowers during the day. It is among the smallest of North American hummingbirds, measuring only 3 to 3.75 inches in length from beak to tail with a wingspread of 4 to 4.75 inches. Both sexes are metallic bronze-green on the crown, nape, back, rump, and middle two tail feathers. Males are gray below with dusky green flanks and sides, whereas females are gray with brownish flanks. Wings and outer tail feathers are dark, with a faint purplish gloss. The female's tail is rounded and has white on the tips of the outer tail feathers, whereas the male's tail lacks the white and is slightly notched. Males have brilliant metallic red throats, which seen in side light may appear golden, greenish, or even dark. The chin and side of the head below the eyes is black. The female’s chin is white.