Metallic green above; white below. Male has metallic ruby throat and black chin; female has white throat and chin spotted with black. Tail and wings green, with white tips on the outer tail feathers of the female. 10 cm (3.9 in) in length. The bill is long and thin.
The breeding season begins in early April, peaks in mid-May to early June, and extends into mid-July. Nesting habitat usually includes bottomland hardwood forests, wooded areas, and thickets, usually near a nectar source. The nest is usually built in a tree 3-6 m (10-20 feet) above the ground. The female constructs the cup-shaped nest out of lichen, spider's webs, and plant down. The female lays 2 eggs that she incubates for 11-14 days. The young are altricial and fledge 14-28 days after hatching. The female cares for the young while they are in the nest, feeding them insects.
Habitat for this species usually includes an area with a nearby source of nectar (flowers or a hummingbird feeder). Nectar is its main food, but its diet also includes insects and tree sap. This species is migratory.
During the breeding season, this species is common to fairly common in the eastern and southeaster United States. Wintering birds occur in northern Mexico south to Costa Rica.
This is the most common species of hummingbird in the eastern United States, but it has been declining in some areas. It is not yet listed for special conservation attention in any part of its southeastern range.
The most similar species to the Ruby-throated Hummingbird is the Black-chinned Hummingbird, a western species whose females and immatures are almost indistinguishable from the Ruby-throated Hummingbird. Male Black-chinned Hummingbirds have a much larger black chin and a metallic-violet band just below the chin. Recently, hummingbirds in the Genus Selasphorus (Broad-tailed, Rufous, and Allen's Hummingbirds) have been more common in the Gulf Coast states during the winter. These species have varying amounts of rufous coloration on their tails and bodies.