Viridian Dacnis (Dacnis viguieri), like most members of the genus, is dichromatic, with blue males and green females. The male is opalescent turquoise and green, with black lores, mantle, and flight feathers. The female is pale olive with dark brown to black lores, wings, and tail feathers. Both the male and female have small black conical bills, gray tarsi, and yellow irides.
Species that are similar to Viridian Dacnis include Blue Dacnis (Dacnis cayana), Green Honeycreeper (Chlorophanes spiza), Turquoise Dacnis (Dacnis hartlaubi), Scarlet-thighed Dacnis (Dacnis venusta), and Viridian's sister species, Black-faced Dacnis (Dacnis lineata). Male Viridian Dacnis is opalescent greenish blue over most of its body, with a distinct black triangle on the mantle, and black on the face confined to the lores; this combination is diagnostic. Male Black-faced Dacnis is further distinguished by its distinctive white or yellow underparts. Scarlet-thighed Dacnis easily is separated, being black underneath with predominantly black wings. The male and female Viridian Dacnis resemble Green Honeycreeper but neither sex has the large, decurved bill of the Green Honeycreeper; furthermore, the mandible of the honeycreeper usually is conspicuously yellow. The female Viridian Dacnis is a paler olive green than are females of Blue Dacnis and Green Honeycreeper, both of which are a much brighter green. The female Scarlet-thighed Dacnis has a brighter yellow belly as well as reddish orange tibial feathers. The female Viridian Dacnis and Black-faced Dacnis are very similar, but Black-faced Dacnis is darker dorsally and brighter yellow or white ventrally. Both sexes of Viridian Dacnis have distinctive yellow irides, while the irides of Blue Dacnis, Green Honeycreeper, and Scarlet-thighed Dacnis are red or reddish brown.
Viridian Dacnis derives its English name from the greenish blue coloring throughout. The head tends to be greener than the body and has dusky lores that form a thin line around the eyes (Wetmore et al. 1984). Males and females are obviously dichromatic, with bright blue males and green females. The male has a green head that fades to a verditer blue that extends down to the breast, belly, and undertail coverts (Meyer de Schauensee 1964). The green head and greenish blue lower back and rump are separated by a black triangular patch on the mantle. As the greenish blue of the rump reaches the uppertail coverts, the color fades to blue. The inner wing coverts and inner remiges are bright olive green edged blue, with contrasting black primaries and outer wing coverts (Meyer de Schauensee 1964, Wetmore et al. 1984, Hilty 2011). Males from Quimarí, Colombia and El Brazo, eastern Panama have bluer sides to the head and nape, and are generally bluer overall, whereas specimens from Juradó have the sides of the head and nape much greener (Meyer de Schauensee 1950, 1951). The female has a dull green head that fades to a rather pale olive green from the nape down to the uppertail coverts, which are olive, tinged with blue (Wetmore et al. 1984). The underparts are paler yellowish olive, with the center of the belly pale buff, that fades yellow to the undertail coverts (Meyer de Schauensee 1964, Wetmore et al. 1984, Hilty 2011). The wings are predominantly dull olive green with dusky outer primaries, edged with greenish. Both rectrices are dusky in both sexes. Additionally, both sexes are highly reflective in the UV spectrum, and this UV coloration is dichromatic (Burns and Shultz 2012).
The subadult male resembles adult females (Isler and Isler 1987, Restall et al. 2007).
Tanagers that have been studied have either a Complex Basic Strategy or Complex Alternative Strategy (Ryder and Wolfe 2009). However, most tanagers only molt once a year, and this prebasic molt likely occurs after the breeding season (Isler and Isler 1987, Ryder and Wolfe 2009). Many species have been found to breed in subadult plumage (Isler and Isler 1987). The performative molt is partial in Dacnis (Ryder and Wolfe 2009). Although a subadult male plumage is described for Dacnis viguieri (Isler and Isler 1987, Restall et al. 2007), more specific information on molt and its timing is not available for this species.
Bill is black, short, conical, and sharply pointed. Irides are yellow and and the tarsi are gray (Hilty and Brown 1986, Restall et al. 2007, Hilty 2011).
The length (sexes combined) is around 9.5-10.5 cm (Wetmore et al. 1984) but has also been reported between 10-11.5 cm (Hilty and Brown 1986, Isler and Isler 1987, Ridgely and Tudor 1989, Restall et al. 2007). Further measurement of individuals from Darién and Colombia can be seen in Table 1.
Table 1. Measurements from Darién and Colombia (Wetmore et al. 1984)
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