Savi’s warbler belongs to the grass warbler genus Locustella. It measures 13–14 cm long. Europe and the western Palearctic are its breeding grounds. A migratory bird, it spends its winters in northern and sub-Saharan Africa.
Savi’s Warblers are similar to River Warblers; eastern migrants pose the most difficulties. Reedbed Locustella with no streaks The overall coloration and habitat preference of this bird are similar to those of the European Reed Warbler. A relatively long bill and a relatively flat or peaked crown also recall European Reed warblers, but the song, wing, and tail structure, as well as behavior, are typical of Locustella warblers.
Compared to European Reeds, Savi’s Warblers are larger and bulkier, with longer, broader, and rounder or square-tipped undertail coverts (often with weak pale scalloping) and a broader and more graduated tail. In general, the wingtips are more broadly triangular, the outer wing margins are more curved (rather than straight edges), the legs and feet are stronger and paler (grayish-pink to dull pink), and there is usually a more obvious pale supercilium behind the eye (but not in front).
A migratory bird, it spends its winters in northern and sub-Saharan Africa.
Likewise, the flanks and undertail coverts are darker, olive-brown (with a tinge of olive-brown extending across the breast), with fairly prominent pale crescents above and below the eye. Freshly plumed birds have brown underparts apart from a white throat, but when worn, the throat, breast, and belly appear whiter.
The nominate race is darker brown than the European reed, especially on the tail, while the eastern race, Fusca, is lighter and more olive-toned. When not singing, it walks through reeds at or near ground level with its tail cocked, dragging itself along furtively with strong feet rather than clambering and hopping at mid-level in reeds. When the song bout ends, it clumsily tumbles into the base of the reeds rather than cocking the tail frequently as an Acrocephalus would. Although it sings in full view on stems, it is otherwise hard to spot as it flits with agility through tangled stems and is rarely seen on open ground.
The Common Grasshopper Warbler can appear unstreaked unless seen well and sings in reed beds. This bird’s skulking behavior and calls are reminiscent of those of the Cetti’s Warbler. It is common to find migrants away from reed beds, walking in bushy cover with a broad tail well-cocked and a low head, and occasionally feeding in low trees, running rapidly along branches and dropping to lower levels in a manner quite different from the Acrocephalus, keeping well hidden at all times.
Adults have abraded wings and tail feathers in autumn, while juveniles have fresh ones. A juvenile’s upper parts are darker and redder brown, with darker centers to wing feathers, in contrast to an adult’s duller, rufous-brown upperparts and more uniformly colored wings. It migrates in juvenile plumage. Some worn and bleached juvenile inner primaries are often retained by young birds until the autumn of their second calendar year.
The call of Savi’s Warbler is an explosive ‘chick’ or ‘tchink’, similar to the mobbing call of the Common Blackbird (and similar to that of Cetti’s Warbler). Savi’s warblers repeat their calls to form a chattering rattle when alarmed. In contrast to the song Common Grasshopper Warbler, it is a continuous, deep, buzzing reel lasting for minutes on end.
The song is distinctly lower in pitch and more rasping in tone, starting with a series of sharp, well-separated notes that accelerate into a continuous buzzing reel (Common Grasshopper starts the song with short bursts of reeling). The Savi’s Warbler sings in an upright posture, usually near the top of reeds at dusk and dawn, but sometimes through the night or day as well.
There are three races. The eastern race fusca (breeds Turkey eastwards) is distinctly more olive-brown, less reddish-brown above, especially in worn plumage, when buffs of underparts also appear lighter than the nominate race or sarmatica.
The Savi’s Warbler is a common bird in the local area. In addition to its mapped range, the Savi’s Warbler breeds in reed beds (sometimes with scattered bushes) by lakes and rivers. Nevertheless, the bird breeds locally in sedge marshes and rush areas. In parks and gardens, where marshy habitats are unavailable, migrant birds live in bushy habitats.
