Like other hummingbirds, the rufous hummingbird feeds on the nectar of flowers, mainly from species with colourful, tubular, short- to medium-length flowers, including columbines (Aquilegia), scarlet gilia (Ipomopsis aggregata), Indian paintbrush (Castilleja), fireweed (Epilobium angustifolium), lilies, larkspurs (Delphinium), currants (Ribes) and heaths (2) (4) (5) (6). It is also a common visitor to artificial hummingbird feeders (2).
The diet of the rufous hummingbird is supplemented with small invertebrates, including gnats, midges, flies, spiders and aphids, which may be caught in the air, plucked from spider webs, or gleaned from plants (2) (4) (6). This species also feeds on the sap of trees such as alder (Alnus) and willow (Salix), through holes excavated by woodpeckers, such as the red-naped sapsucker (Sphyrapicus nuchalis) (4) (5) (6). Sap and insects are often taken when the hummingbirds first arrive at the breeding grounds, when few spring flowers are available (4) (5). The rufous hummingbird is also able to enter a temporary state of torpor to survive periods of food shortage (4).
The rufous hummingbird is aggressively territorial, defending patches of flowers not only during breeding, but also on temporary stop-overs during migration (4). At all times of year, this belligerent small bird will attack any visiting hummingbirds, including larger species (2) (4) (5), and has even been seen chasing chipmunks from its nests (2).
The breeding season of the rufous hummingbird runs from March to July (4) (5) (6). The male rufous hummingbird performs a display flight as part of courtship, calling while flying in a steep oval or in the shape of a ‘J’. If the female perches, the male may fly in a series of horizontal figure-eights (2) (4) (5), a display that is also sometimes directed at competitors and intruders on the territory (4) (5). The nest of this species is built by the female alone, and consists of a small cup of soft plant down, covered on the outside with lichens, moss and bark, which are held together with spider webs (2) (4) (5) (6). The nest is usually well hidden in a shrub, conifer or oak tree (2) (4) (5), and small colonies of up to 20 nests have sometimes been reported (2) (6).
The rufous hummingbird lays 2 to 3 eggs, which are incubated by the female for 15 to 17 days (2) (4) (5) (6). The chicks leave the nest after about 20 to 26 days (4) (6). The rufous hummingbird is surprisingly long-lived, with the oldest recorded individual surviving for over eight years (2) (4).