The common grasshopper warbler (Locustella naevia) is a small passerine bird found in short dense vegetation, often close to water. It is a medium-sized warbler about 13 cm (5 in) long. The adult has a streaked brown back and whitish grey underparts which are unstreaked except on the undertail coverts. The sexes are identical, as with most warblers, but young birds are yellower below. Like most warblers, it is insectivorous. Four to seven eggs are laid in a nest on or near the ground in thick vegetation or in a tussock of grass.
This is a species which skulks in the undergrowth, creeping through bushes and low foliage, and which is very difficult to see except sometimes when singing from a prominent position. The song, which gives this species its name, is a monotonous mechanical insect-like reeling, often given at dawn or dusk.
This bird seldom takes to the wing but spends its time scurrying through dense vegetation, flitting from twig to twig or running along the ground. It has a peculiar high-stepping gait and long stride as it moves along horizontal stems, looking slender and tapering. It seldom flies, soon diving back into cover, and when it alights it often raises and flares its tail to show its streaked under-tail coverts. It has been known to feign injury in order to distract a potential predator.