White-tailed Hummingbird

The White-tailed Hummingbird, Eupherusa poliocerca, is a diminutive and radiant bird, measuring a mere 10 to 11 centimeters in length and tipping the scales at a lightweight 4.5 to 5 grams. This species is adorned with a straight black bill, a feature shared by both males and females.

Identification Tips

Males boast a lustrous metallic bronze-green plumage on their upperparts, with rufous primaries and secondaries creating a conspicuous patch on the folded wing. The central pair of tail feathers gleam with a metallic bronze-green sheen, while the remaining four pairs are a muted grayish white. Their underparts are a vibrant metallic yellowish green, complemented by white undertail coverts. Females, on the other hand, display bright metallic golden-green upperparts and a similar wing patch to the males. Their central tail feathers share the same metallic golden-green hue, with the rest being white, tinged with dusky or bronze-green. The underparts of females are a more subdued grayish white, with metallic green speckles on the sides and undertail coverts ranging from white to grayish white.

Habitat

The White-tailed Hummingbird is a denizen of the humid montane, semi-deciduous, and pine-oak forests, as well as plantations. It shows a preference for the edges and interiors of these habitats and is notably absent from shade coffee plantations.

Distribution

Endemic to southwestern Mexico, this species graces the Pacific slope of Guerrero and extends marginally into western Oaxaca.

Behaviour

While the details of the White-tailed Hummingbird's movements remain somewhat enigmatic, it is suspected that they may undertake seasonal elevational migrations.

Feeding

This hummingbird is an adept forager, seeking nectar across all strata of the forest, from the understory to the lofty canopy. It is known to frequent the flowers of Inga, Lobelia, Malvaviscus, and Psittacanthus, among others. Although not extensively documented, it is also believed to consume small arthropods, as is typical for hummingbirds.

Breeding

The breeding habits of the White-tailed Hummingbird are not well-documented. However, the condition of specimens suggests two peaks in breeding activity: one from February to May and another from September to October. The architecture of its nest remains a mystery.

Vocalization

The song of the White-tailed Hummingbird is characterized as a high, rapid, and slightly liquid to squeaky warble. Its calls include a liquid to slightly buzzy, rolled chip, which can transition into rattled trills.

Conservation status

The IUCN has classified the White-tailed Hummingbird as Near Threatened. With an estimated population of fewer than 15,000 mature individuals, the species is believed to be in decline. Habitat destruction and threats from logging and agricultural expansion continue to imperil the remaining forest within its range. The Mexican authorities have recognized the species as threatened.