A jewel of high mountain meadows, male Broad-tailed Hummingbirds fill the summer air with loud, metallic trills as they fly. They breed at elevations up to 10,500 feet, where nighttime temperatures regularly plunge below freezing. To make it through a cold night, they slow their heart rate and drop their body temperature, entering a state of torpor. As soon as the sun comes up, displaying males show off their rose-magenta throats while performing spectacular dives. After attracting a mate, females raise the young on their own.
Broad-tailed Hummingbirds breed in meadows and open woodlands, especially pinyon-juniper, pine-oak, evergreen, and montane scrub and thickets from around 5,000–10,500 feet elevation. During migration they move through highland meadows to lowlands with abundant flowers. In winter, they forage in pine-oak forests, dry thorn forests, and tropical highlands throughout Mexico
Broad-tailed Hummingbirds drink nectar from flowers, especially species such as larkspur, red columbine, indian paintbrush, sage, and scarlet gilia as well as sugar water from feeders. During spring migration, they also feed on flowers that are not typically used by other hummingbirds, including pussy willow, currant, and glacier lily. Nectar is a low-protein food, so they also eat small insects, especially nesting females, and feed insects to their nestlings. They glean insects from leaves, snatch them from midair, or pick them out of spiderwebs. Sometimes they use sap as a nectar substitute, visiting sapwells excavated by Red-naped Sapsuckers.
Broad-tailed Hummingbirds hover to snatch insects from the air or above flowers to drink nectar. When hovering, they beat their wings at about 50 wingbeats per second. Males also hover above tall vegetation to keep an eye out over their territory, chasing away unwelcome visitors. During courtship males perform spectacular aerial displays for females, involving a series of climbs and dives while loudly trilling their wings. Males climb high into the sky and rapidly dive toward the ground, pulling out of the dive in front of a female. If a male loses sight of a female, he hovers high above the ground and looks around for her. Despite the elaborate displays, males don't form pair bonds and are promiscuous; males often mate with several females in one breeding season. Males also do not feed incubating females or care for the young even after they fledge. When the nights are cold or if they cannot obtain enough food to keep their body temperature up, it is not uncommon for both sexes, to go into a hypothermic torpor at night. In torpor they slow their heart rate and drop their body temperature to save energy. Because males are not caring for their young, they can also leave their territories at night when cold air descends into the breeding area, seeking warmer areas elsewhere.
Females build and tend the nests alone. The female builds a tiny cup-shaped nest out of spiderwebs and gossamer, which provides excellent insulation, and helps conserve heat in the cold of high altitudes. It is often placed under overhanging branches, keeping the nest warmer than surrounding areas, and reducing nighttime energy requirements of the incubating female. She forms the nest cup by twisting the material around with her body and feet while sitting in the nest. The thick inner cup is made out of spiderweb and gossamer, and after forming the cup, she camouflages the outside of it with bits of lichen, moss, and bark fragments. Material may be stolen from other nests and is frequently added during incubation, with the nest sometimes becoming taller over time. It takes about 4–5 days for her to build a nest, less if built upon a previous nest. The nest has an outer diameter of about 2 inches and a 0.8-inch inside diameter, but it stretches as the chicks grow, becoming more platform shaped. Sometimes the female will reuse a nest from a previous season, adding fresh material to what was left.
© Paul Marvin | Macaulay Library
Small bird; medium-sized hummingbird. Shiny green upperparts. Adult male has red throat. Adult female has white throat speckled with iridescent green or bronze.
Resembles adult female, with more spotting on throat.
Female and juvenile hummingbirds can be extremely difficult to identify. Female Allen's and Rufous Hummingbirds are slightly smaller than female Broad-tailed Hummingbirds and they have shorter tails. Female and juvenile Anna's Hummingbirds have a white arc over the eye that extends down the side of the face, instead of the pale eyering on female Broad-tailed Hummingbirds. Anna's Hummingbirds also tend to have dingier breasts than Broad-tailed Hummingbirds. Ruby-throated Hummingbirds occur in the East and generally do not overlap with Broad-tailed Hummingbirds. But in areas in Texas where they could overlap during migration, Ruby-throated Hummingbirds have a blackish or dark gray ear patch not seen on Broad-tailed Hummingbirds.
- The Broad-tailed Hummingbird enters torpor, a slowed metabolic state, on cold nights. It maintains a body temperature of about 12.2°C (54°F) when ambient temperatures fall below 10°C (44°F).
- In some areas of Broad-tailed Hummingbird breeding habitat, cold air descends into valleys at night, with warmer areas upslope. This phenomenon is called a thermal inversion. The male Broad-tailed Hummingbird, which does not attend the nest, goes upslope at night to conserve heat, reducing the energy costs of thermoregulation by about 15 percent.