White-tailed Emerald

The White-tailed Emerald, scientifically known as Microchera chionura, is a diminutive and radiant hummingbird belonging to the emeralds tribe, Trochilini, within the subfamily Trochilinae. This species exhibits a striking sexual dimorphism in plumage coloration.

Identification Tips

Adult males of the White-tailed Emerald species are characterized by bronzy green upperparts that transition to a dark copper-bronze hue on the uppertail coverts. Their central tail feathers mirror the copper-bronze of the coverts, while the remaining tail feathers are predominantly white with black tips. A glittering green throat and chest complement their white belly, vent, and undertail coverts. Females, on the other hand, display bronzy green upperparts with central tail feathers of a similar bronzy shade, and the other tail feathers are white with a distinct black band near the tip. Their underparts are a muted white with bronzy green flanks. Immature males resemble the adults but have less vibrant underparts with grayish buff fringes, while immature females have grayer underparts compared to the adult females.

Habitat

The White-tailed Emerald is known to inhabit the edges and interiors of moist to humid montane forests, secondary forests, as well as plantations and gardens. Males are often found in the forest canopy, while females prefer the understory.

Distribution

This species is endemic to the highlands of the Pacific slope, ranging from south-central Costa Rica to central Panama, and is also found locally on the Caribbean slope in Panama.

Behaviour

The movements of the White-tailed Emerald are not fully understood, but some individuals in Costa Rica are known to migrate both upslope and down outside the breeding season.

Song & calls

The song of the White-tailed Emerald is a prolonged, thin, scratchy twittering mixed with buzzing or gurgling notes. When foraging, it emits soft scratchy chipping notes, and during chases, it produces high-pitched, buzzy notes.

Breeding

The breeding season for the White-tailed Emerald spans from June to November. Males engage in courtship displays at leks in small groups. However, the specifics of their breeding phenology and nest characteristics remain undocumented.

Diet and Feeding

Nectar from a variety of flowering plants constitutes the primary diet of the White-tailed Emerald. They forage at both the forest edges and interior. Additionally, they capture small arthropods by hawking from a perch.

Conservation status

The IUCN has classified the White-tailed Emerald as Least Concern, with an estimated population of at least 20,000 mature individuals that appears to be stable. While the species is locally common in some protected areas, deforestation poses a threat, particularly in the lower part of its altitudinal range.