Physical characteristics

The traits that have been used to characterize Sylviidae sensu latu are: unspotted young (as opposed to the Old World flycatchers and thrushes); rictal bristles at the base of the bill (a widespread adaptation for insectivory); thin, pointed bill; hatchlings naked or only partially downy; ten primaries; scutellate tarsi; and lack of strong sexual dimorphism (Sylvia is a notable exception). Most genera have twelve tail feathers, but there are a few exceptions. Wing shape and length ranges from short and rounded in sedentary species, to longer and more pointed in long-distance migrants. Moult timing and pattern are highly variable.

Sylviids are typically dull in color; often in shades of brown, green, yellow, and gray. The family includes some of the tiniest songbirds in the world, the kinglets, as well as some small wren-like birds, many small warblers, and the medium-sized marsh warblers and grassbirds. The smallest sylviids, the kinglets, weigh only a few grams. The largest, the marsh warblers Acrocephalus and the grassbirds Megalurus can weigh close to 2 oz (60 g). A comprehensive summary of longevity data is unavailable, but many species live at least 8-12 years.

While most species do not have distinctive breeding plumages like those of the New World warblers (Parulidae), a few sylviids show a marked contrast between breeding and nonbreeding plumages. A striking example is the red-winged warbler (Heliolais erythroptera), the only member of a genus apparently closely related to Prinia. While breeding red-

winged warblers of both sexes have dark gray upperparts and tail, they become predominantly tawny-brown in nonbreed-ing plumage. A somewhat less striking example is the genus Cisticola. Members of this genus undergo two moults each season, and most have shorter tails and slightly different plumage coloration during the breeding season. A few members of the genus Prinia have similar distinct seasonal plumage variation.

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