Trogon - Morphology and Flight

Morphology and Flight

The trogons as a family are fairly uniform in appearance, having compact bodies and long tails (very long in the case of the quetzals), and short necks. Trogons range in size from the 23 cm, 40 gram Scarlet-rumped Trogon to the 40 cm, 210 gram Resplendent Quetzal (not including the male quetzal's 3-foot-long (0.91 m) tail streamers). Their legs and feet are weak and short, and trogons are essentially unable to walk beyond a very occasional shuffle along a branch. They are even incapable of turning around on a branch without using their wings. The ratio of leg muscle to body weight in trogons is only 3 percent, the lowest known ratio of any bird. The arrangement of toes on the feet of trogons is also unique amongst birds, although essentially resembling the zygodactyl’s two forward two backward arrangement of parrots and other near-passerines, the actual toes are arranged with usually inner hallux being the outer hind toe, an arrangement that is referred to as heterodactylous. The strong bill is short and the gape wide, particularly in the fruit eating quetzals, with a slight hook at the end. There is also a notch at the end of the bill and many species have slight serrations in the mandibles. The skin is exceptionally tender, making preparation of study skins difficult for museum curators. The skeletons of trogons are surprisingly slender, particularly the skulls which are very thin. The plumage of many species is iridescent, although most of the Asian species are not. The African trogons are generally green on the back with red bellies. The New World trogons similarly have green or deep blue upperparts but are more varied in their lowerparts. The Asian species tend towards red underparts and brown backs.

The wings are short but strong, with the wing muscle ratio being around 22% of the body weight. In spite of the strength of their flight, trogons do not fly often or for great distances, generally flying no more than a few hundred metres at a time. Only the montane species tend to make long distance flights. Shorter flights tend to be direct and swift, but longer flights are slightly undulating. Their flight can be surprisingly silent (for observers), although that of a few species is reportedly quite noisy.