Chlorostilbon mellisugus (Linnaeus, 1758)

Sexual Size Dimorphism

The blue-tailed emerald, Chlorostilbon mellisugus, has distinct size differences between males and females. Males range in length from 7.5 to 9.5 cm (3.0 to 3.7 in), while females are 6.5 to 7.5 cm (2.6 to 3.0 in) long.

Subspecies Weight

For two commonly recognized subspecies, the average weights are consistent: males of both C. m. caribaeus and C. m. phoeopygus average about 2.7 g (0.095 oz), while females of C. m. caribaeus average 2.5 g (0.088 oz) and females of C. m. phoeopygus average 2.4 g (0.085 oz). Across all subspecies, both sexes share a short, straight, black bill.

Tail Morphology

All males have a forked tail, with fork depth varying slightly between subspecies, and females of all subspecies are essentially indistinguishable from one another.

Nominate Male Plumage

The nominate subspecies (C. m. mellisugus) males have an iridescent golden green forehead and crown, shining bronze-green upperparts, a steel blue tail, and glittering emerald green underparts that are most iridescent on the breast and carry a bluish tint on the throat; they also have white thighs.

Nominate Female Plumage

Nominate females have a bronzy green forehead and crown, a blackish facial "mask" with a pale gray stripe behind the eye, metallic grass green upperparts, a blue-black tail with whitish gray tips, and pale gray underparts.

C. m. caribaeus Traits

C. m. caribaeus is very similar to the nominate, but males have less blue on the throat.

C. m. duidaes Traits

Male C. m. duidaes have a bronzy orange head and reddish copper upperparts.

C. m. subfurcatus Traits

Male C. m. subfurcatus have blue-green throats and uppertail coverts and golden green crowns, with color intensities that fall between those of the nominate and C. m. caribaeus.

Other Subspecies Traits

C. m. phoeopygus has a deeper tail fork than the nominate, and C. m. peruanus looks essentially identical to the nominate.

Taxonomic Status

The International Ornithological Congress recognizes seven subspecies of blue-tailed emerald, each with distinct distributions.

C. m. caribaeus Distribution

C. m. caribaeus is found in northern Venezuela, Trinidad, and the ABC Islands.

C. m. duidae Distribution

C. m. duidae occurs in the Cerro Duida region of southern Venezuela's Amazonas state.

C. m. subfurcatus Distribution

C. m. subfurcatus ranges across eastern and southern Venezuela, Guyana, and the Rio Branco region of northwestern Brazil.

C. m. mellisugus Distribution

The nominate C. m. mellisugus is found in Suriname, French Guiana, and the lower Amazon basin of northeastern Brazil.

C. m. phoeopygus Distribution

C. m. phoeopygus occurs along the upper Amazon River and its eastern tributaries in Colombia, Ecuador, and Brazil.

C. m. napensis Distribution

C. m. napensis is found along the upper Amazon River in northeastern Peru.

C. m. peruanus Distribution

C. m. peruanus ranges across southeastern Peru, eastern Bolivia, and possibly extreme southwestern Brazil.

Habitat General Range

This species inhabits a wide range of landscapes from tropical to temperate zones.

Common Habitats

It occurs most often in semi-open to open areas including savanna, cerrado, cultivated areas, and gardens. It can also be found at the edges of deciduous woodland, in large clearings within terra firme forest, and is common in várzea and floodplain forest in Ecuador.

Elevation Range

Its elevation range varies by country: in Ecuador it occurs between 750 and 2,600 m (2,500 and 8,500 ft), in Peru it occurs up to 1,200 m (3,900 ft), and in Venezuela it ranges from sea level to about 1,850 m (6,100 ft).