About Microchera chionura (Gould, 1851)
The white-tailed emerald (Microchera chionura) measures 7.5 to 8 centimeters (3.0 to 3.1 inches) in total length. Males weigh approximately 3.3 grams (0.12 ounces), while females weigh 3.1 grams (0.11 ounces). Both sexes share an almost straight black bill, with a pinkish base on the mandible. Adult males have bronzy green upperparts that darken to copper-bronze on the uppertail coverts. Their central two pairs of tail feathers are copper-bronze, and the outer three pairs are white with black tips. Adult males have a glittering green throat and chest, with white belly, vent, and undertail coverts. Adult females also have bronzy green upperparts. Their central two pairs of tail feathers are bronzy, and the outer three pairs are white with a black band near the tip. Female underparts are dull white, with bronzy green flanks. Immature males resemble adult males but have duller underparts, with grayish buff feather fringes. Immature females have grayer underparts than adult females. The white-tailed emerald occurs in the highlands of the Pacific slope, ranging from south-central Costa Rica to central Panama, and is also found locally on Panama's Caribbean slope. It inhabits the edges and interior of moist to humid montane forest and secondary forest, and also occurs in plantations and gardens. Within forest interiors, males are often found in the canopy while females occupy the understory. This species occurs at elevations between 750 and 2,000 meters (2,500 to 6,600 feet); in Costa Rica, it breeds mostly between 1,000 and 1,700 meters (3,300 to 5,600 feet).
