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Tuesday, October 16, 2007

Broadtail Hummingbird


A hummingbird of subalpine meadows, the Broad-tailed Hummingbird ranges across the south-central Rockies in summer. It possesses a number of physiological and behavioral adaptations to survive cold nights, including the ability to enter torpor, slowing its heart rate and dropping its body temperature.

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.

* Size: 8-9 cm (3-4 in)
* Wingspan: 13 cm (5 in)
* Weight: 3-4 g (0.11-0.14 ounces)

Small bird; medium-sized hummingbird. Shiny green upperparts. Adult male has red throat. Adult female has white throat speckled with iridescent green or bronze.

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