Wrens are medium-small to very small birds. The Eurasian wren is among the smallest birds in its range, while the smaller species from the Americas are among the smallest passerines in that part of the world. They range in size from the white-bellied wren, which averages under 10 cm (3.9 in) and 9 g (0.32 oz), to the giant wren, which averages about 22 cm (8.7 in) and weighs almost 50 g (1.8 oz). The dominating colors of their plumage are generally drab, composed of gray, brown, black, and white, and most species show some barring, especially to tail and/or wings. No sexual dimorphism is seen in the plumage of wrens, and little difference exists between young birds and adults. All have fairly long, straight to marginally decurved bills. Wrens have loud and often complex songs, sometimes given in duet by a pair. The song of members of the genera Cyphorhinus and Microcerculus have been considered especially pleasant to the human ear, leading to common names such as song wren, musician wren, flutist wren, and southern nightingale-wren.