Ruby-throated hummingbirds are 7.5 to 9.0 cm long and weigh approximately 3.4 g to 3.8 g. Their back and head are iridescent green, with white underparts. Males are easily disquished from females because of their brilliant red metallic throat and forked tail. Females have a dull grayish throat, and a square, white-tipped tail. Immature ruby-throats appear similar to adult females, however sometimes young males may have a few red feathers on their throat.
Male ruby-throated hummingbirds return to the breeding area first. They establish a territory before the females arrive. When the females arrive, the males court females by performing courtship displays that can include erecting their red throat feathers and harassing the female and performing a “dive display” by flying in looping dives above the females head. When the female perches, the male can fly in very rapid horizontal arcs in front of the female. The male's wings can beat up to 200 times per second during these displays. After copulation, the male and female separate. These birds do not establish breeding pairs. They separate after copulation. The females select the nesting site and build the nest. It's made of plant materials including thistle and dandelion but may include spider webs and pine resin. The outside is often covered with lichens.
When the nest is completed 1 to 3 eggs are laid and incubated between 10 and 14 days, exclusively by the female. The young are hatched in a relatively underdeveloped state; unable to feed or care for themselves or locomote independently.The chicks leave the nest 18 to 22 days after hatching but the female continues to feed them for 4 to 7 days after they fledge.The male provides no parental care whatsoever.
Ruby-throated hummingbirds live alone. Adults come into contact for the purpose of mating only. Males are territorial, and communicate with each other primarily through vocalizations. They are active during the day but in the cool temperatures of nights ruby-throated hummingbirds save energy by allowing the body to cool down several degrees, and body functions slow down to conserve energy.
Many ruby-throated hummingbirds migrate as far as 1,600 km roundtrip each year, flying non-stop across the Gulf of Mexico. In order to complete this grueling journey, these hummingbirds often double their body mass before beginning migration. The return flight to breeding grounds is timed so that arrival coincides with flowering of food plants in a given region.
References:
Robinson, T., R. Sargent, M. Sargent. 1996. Ruby-throated hummingbirds (Archilochus colubris). Pp. 1-16 in A. Poole, F. Gill, eds. The Birds of North America, Vol. 204. Philadelphia, PA: The Academy of Natural Sciences and Washington DC: The American Ornithologists Union.Bull, John. Birds of New York State. Cornell University Press, 1974.Tyrell, Esther, Quesada. Hummingbirds: Their Life and Behavior. Crown Publishers Inc., 1985.
