White-tailed Goldenthroat

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White-tailed Goldenthroat

Quick Facts

  • Scientific Name: Polytmus guainumbi
  • Spanish Name: Colibrí coliblanco
  • Family: Trochilidae
  • Known Nicknames: White-tailed Goldenthroat, Guainumbi
  • Average Length: 8.5–10 cm / 3.3–3.9 in
  • Average Weight: 3–5 g / 0.11–0.18 oz
  • Wingspan: 11–13 cm / 4.3–5.1 in
  • Key Feature: Iridescent golden-green throat and white-tipped outer tail feathers
  • Primary Diet: Nectarivore, Insectivore
  • Range: Northern and central South America (Colombia to Brazil, Bolivia, and Argentina)
  • Habitat: Savannas, grasslands, open woodlands, and gallery forests
  • Social Structure: Solitary
  • Nesting/Breeding: Small cup-shaped nest in a shrub or tree fork
  • Conservation Status: Least Concern (LC)
  • Population Trend: Stable

The White-tailed Goldenthroat (*Polytmus guainumbi*) is a dazzling hummingbird endemic to the savannas and open grasslands of northern South America, most notably the Venezuelan Llanos. Its most striking feature is the male's brilliant, iridescent golden-green throat that flashes like a jewel in the sun, contrasting sharply with a velvety black mask and a long, deeply forked, pure white tail—a unique combination that gives the species its name. Females are more subdued, with a whitish throat and a shorter, white-tipped tail, but both sexes share a slender, slightly decurved black bill perfectly adapted for sipping nectar from tubular flowers. A special adaptation of this species is its preference for foraging low to the ground, often hovering near termite mounds or wetland edges, making it one of the few hummingbirds that actively avoids dense forest canopies. Its rapid, direct flight and the male's dramatic aerial displays, where he fans his white tail feathers to attract mates, make the White-tailed Goldenthroat a vibrant and charismatic inhabitant of its sun-drenched grassland home.

Fun Facts

The White-tailed Goldenthroat is a master of aerial acrobatics, often seen hovering with its tail cocked upward at a dramatic angle, a posture that helps it balance while extracting nectar from deep, curved flowers that other hummingbirds can’t reach. Unlike most hummingbirds, it has a peculiar habit of occasionally perching on the ground to sunbathe, spreading its wings and tail flat to absorb heat—a behavior rare among its family. Its iridescent golden throat isn’t just for show; males use it in aggressive “shimmer displays” to reflect flashes of light at rivals, blinding them momentarily during territorial chases. Remarkably, this bird can enter torpor on warm nights, a state of deep sleep that drops its heart rate from over 1,000 beats per minute to just 50, saving energy in its tropical but resource-scarce savanna habitat.

Habitats & Distribution

The White-tailed Goldenthroat is predominantly found in open and semi-open lowland habitats, favoring areas near water such as river edges, flooded savannas, and the margins of gallery forests. It also inhabits scrublands, grasslands with scattered bushes, and occasionally disturbed areas like pastures and clearings, but generally avoids dense, humid forests. Its geographical range spans a broad swath of South America east of the Andes, from eastern Colombia and Venezuela through the Guianas, across much of Brazil, and southward into eastern Bolivia, Paraguay, and northeastern Argentina, including the Pantanal region.

Behaviours & Reproduction

Males are solitary and aggressively territorial, defending feeding areas rich in nectar-producing flowers. During courtship, the male performs a distinctive U-shaped dive display, producing a sharp, mechanical whirring sound with his tail feathers to attract a female. There is no pair bond; the male departs immediately after mating. The female alone builds a small cup-shaped nest, typically in a fork of a shrub or low tree, using plant down and spider webs. She lays two white eggs and incubates them for about 14–16 days. A unique reproductive strategy is the female’s ability to enter a state of torpor overnight during incubation to conserve energy, lowering her metabolic rate and body temperature, then reviving at dawn to resume feeding and brooding.

Diet

The White-tailed Goldenthroat is a specialized nectarivore, feeding primarily on the high-energy nectar of a variety of flowers, particularly those with long, tubular corollas such as members of the Rubiaceae, Acanthaceae, and Bromeliaceae families. It uses its long, extendable tongue to lap up nectar while hovering, and like many hummingbirds, it must consume up to twice its body weight in nectar daily to fuel its incredibly high metabolism. Interestingly, this diet is supplemented with small insects and spiders, which provide essential proteins, amino acids, and fats that nectar lacks; the bird often catches these arthropods in flight through a technique called "hawking," or by gleaning them from leaves and spider webs. Another notable fact is that the White-tailed Goldenthroat plays a crucial role as a pollinator for many neotropical plants, transferring pollen on its head and bill as it moves between flowers in its savanna and grassland habitats.

Colors

The White-tailed Goldenthroat is a hummingbird with predominantly iridescent golden-green upperparts and a glittering emerald-green throat. Its underparts are a paler, grayish-green, while the most distinctive feature is its white outer tail feathers contrasting sharply with dark central ones. The male has a slightly forked tail and a long, straight, black bill. This green plumage provides excellent camouflage against dense foliage, while the white tail markings may serve as a visual signal during courtship.

Distribution Map

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