The Green-headed Tanager is an average size member of the large genus Tangara. Like many other species in this genus, it is richly patterned with multiple, vibrant colors. These include turquoise, yellow-orange, bright lime green, violet, and black. The head is primarily light bluish green, with a broad yellow-green band across the nape and upper back. The throat and back are black; the belly is bright blue; and the rump is orange. The flanks and the edges to the wing feathers are bright yellowish green. The sexes are very similar to one another, but the females tend to be slightly duller.
The Green-headed Tanager has a similar plumage pattern to both the Seven-colored Tanager (Tangara fastuosa) and Paradise Tanager (Tangara chilensis) (Isler and Isler 1987). All three species have a greenish or bluish head, black on the back, and a contrastingly colored, orange or red rump. Although there is similarity between the species, the Green-headed Tanager is easily distinguished by the yellowish green band across its nape and upper back as well as its bright green flight feathers and tail coverts. Furthermore, the distributions of these three species do not overlap (Isler and Isler 1987).
Adult male: One of the most complex patterned species of Tangara. Although named the Green-headed Tanager, the head is more turquoise-green than green. A bright yellow-green band extends around the head from the nape to upper back. Rest of back is black, rump is orange, and uppertail coverts are bright yellow-green. Throat is black, breast and upper belly turquoise, lower belly and crissum bright yellow-green. There are black feathers around the bill as well as a small black eye ring. The wing coverts are a combination of purple and blue, flight feathers are black and broadly edged with bright green (Isler and Isler 1987, Ridgely and Tudor 2009).
Adult female: Very similar to the male, but slightly duller (Perlo 2009, Ridgely and Tudor 2009).
Juvenile/subadult: Similar to adult, but duller (Isler and Isler 1987).
In general, most tanagers only molt once a year (Isler and Isler 1987), and this prebasic molt likely occurs after the breeding season (Isler and Isler 1987, Ryder and Wolfe 2009). However, many species, including Tangara seledon, sre known or are suspected to breed in subadult plumage (Isler and Isler 1987). In many species of Tangara, the preformative molt is partial (Ryder and Wolfe 2009). Although a subadult plumage is described for Tangara seledon (Isler and Isler 1987), more specific information on molt and its timing is not available for this species.
Iris: dark brown
Tarsi and toes: dark gray to black
Bare part color data from Hilty (2011).
Measurements include both male and female (Isler and Isler 1987)
| Total Length|| Mass|
| 13 cm|| 18g (16-20 g; n = 3)|