About Locustella certhiola (Pallas, 1811)
Locustella certhiola is a medium-sized warbler. Adult individuals have a streaked brown back, whitish grey underparts that are unstreaked except on the undertail. Like most warblers, the sexes are identical in appearance, while young birds are yellower on their underparts. This species is insectivorous, as most warblers are. It is very similar to the common grasshopper warbler, but is slightly larger, has white tips on its tail and tertial feathers, and a warmer brown rump. These white tail and tertial tips give the species its colloquial mnemonic name of "PG Tips". This is a skulking species that is very hard to see, only occasionally visible when singing. It creeps through grass and low foliage. As a small passerine bird, it inhabits tall grass with thicker vegetation, typically located near water in bogs or wet meadows. It lays a clutch of 4 to 7 eggs in a nest built on the ground within grass. This species is a very rare vagrant to western Europe. One of the best sites to see this skulking species as a vagrant is Fair Isle, Shetland; even though it only rarely occurs in western Europe, it can be found there with some regularity.
