The trumpeters are a family of birds restricted to the humid forests of the Amazon and Guiana Shield in South America. They are named for the trumpeting or cackling threat call of the males. The three species resemble chickens in size; they measure 45 to 52 centimetres (18 to 20 inches) long and weigh 1 to 1.5 kilograms (2.2 to 3.3 pounds). They are dumpy birds with long necks and legs and curved bills and a hunched posture. Their heads are small, but their eyes are relatively large, making them look "good-natured". The plumage is soft, resembling fur or velvet on the head and neck. It is mostly black, with purple, green, or bronze iridescence, particularly on the wing coverts and the lower neck. In the best-known taxa the secondary and tertial flight feathers are white, grey, or greenish to black, and hairlike, falling over the lower back, which is the same colour. These colours give the three generally accepted species their names.