The green-backed trogon (Trogon viridis), also known as the Amazonian white-tailed trogon, is a near passerine bird in the trogon family. It is found in tropical humid forests in South America, where its range includes the Amazon, the Guiana Shield, Trinidad, and the Atlantic Forest in eastern Brazil. It formerly included T. chionurus of the Chocó region as a subspecies, but under the common name white-tailed trogon (a name now reserved for T. chionurus).
This relatively large trogon is 28 to 30 centimetres (11 to 12 in) long. As most trogons, it is strongly sexually dimorphic. In the male the head and upper breast are dark blue (appears blackish in poor light), and the back is green. The lower underparts are orange yellow. The wings are black, vermiculated with white. The undertail is black and white: Each feather has a broad black base and a broad white tip and outer edge. The complete eye-ring is pale bluish. The female green-backed trogon resembles the male, but has a grey back, head and breast, and distinct black-and-white barring mainly to the outer webs of each tail feather.
For comparison, the similar but smaller violaceous trogon has a yellow (male) or incomplete white eye-ring (female), and the male also has barring to the undertail.
There is no overlap in the distribution of the green-backed and white-tailed trogons, but the two can be separated by the undertail pattern: Unlike the green-backed trogon, the male white-tailed trogon only has a very narrow black base to each feather (the undertail appears almost entirely white), and the female mainly has black-and-white barring to the inner webs of each feather (can be difficult to see). The male white-tailed trogon also has a bluer rump than the green-backed trogon.
The song of the green-backed trogon consists of about 20 cow notes that start slow, but accelerate towards the end. The song is slower than the white-tailed trogon, and higher pitched than the black-tailed trogon. source