Grasshopper Warbler

Locustella naevia

12.5cm

Appearance

The Grasshopper Warbler is inconspicuous and is smaller than a House Sparrow. It is olive-brown above with some streaking, and it is buffish below with a few dark streaks beneath the tail and on the breast. There's a pale strip across the eye. The feathers on the undertail are long and darkly streaked, while the wings are stumpier with rounded ends. Juveniles appear yellower than adults; the plumage is more vivid, particularly on the underparts.

Habitat

The Grasshopper Warbler needs thick cover on the ground with some open spaces; it is widespread in the region, though not numerous. Breeding takes play in lowland habitats, either wet or dry, including scrub, thickets, margins of marshes, heaths, grassland, newish forest plantations and gravel pits with vegetation.

Character

This is a timid bird that is more likely to be heard than seen, although fresh migrants may sing from more exposed parts of bushes. When courting, birds may dart between bushes, and move wings above their backs in display habits. Stays grounded most of the time, and can slip away to cover very effectively if disturbed.

Food

Diet includes bugs, beetles, moth caterpillars, lacewings, flies and ants, and Grasshopper Warblers also feed on elderberries towards the end of summer.

Breeding

Female lays 5 or 6 eggs and both parents incubate for 12-15 days; both parents also share the job of feeding the young for 12-13 days. In northern territories there is usually just the one brood, while birds in southern territories of the region usually raise two broods.

Population

The Grasshopper Warbler is a summer visitor to the region, arriving between the middle of April and May, with some from farther afield in the north or east arriving in September. Most birds depart through July and August; their passage is primarily flown at nighttime, with lengthy non-stop flights. Numbers in the UK are usually around 16 000 pairs or fewer, and Ireland numbers are around 2500-10 000.

Observation Tips

This bird is best located by listening to its song, and though it can be difficult to see, some birds will occasionally sing from a visible perch.

Voice

Song can sound quite insect-like and can be held at length without a pause; this trill has been compared to the mechanism on a fishing pole reel. Birds move their head gently and slowly from side to side as they sing, and are mostly likely to sing between April and July, particularly as the sun rises or sets. Also has an acute 'tssvet' call.
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