About Iduna opaca (Cabanis, 1850)
Iduna opaca, commonly known as the western olivaceous warbler, is a small migratory passerine bird. This species inhabits dry open country including cultivated areas that have bushes or scattered trees. It is a medium-sized warbler, with an appearance more similar to a very pale reed warbler than to its close relative the melodious warbler. Adult western olivaceous warblers have a plain pale brown back and whitish underparts. The species has a body length of approximately 13–14 centimetres (5.1–5.5 in), a wingspan of 18–21 centimetres (7.1–8.3 in), and a weight between 8–13 grams (0.28–0.46 oz). It has a strong, pointed bill and grey legs. Like most warblers, males and females have identical plumage, while young birds have more buff colouring on the belly. This species rarely, if ever, wiggles its tail, and it searches for food at a range of different heights. Like most warblers, the western olivaceous warbler is insectivorous. It builds its nest in low undergrowth or a bush, and lays a clutch of two or three eggs. The species breeds in Iberia and north Africa, and is migratory, wintering in sub-Saharan Africa. It is a rare vagrant to northern Europe. Compared to the eastern olivaceous warbler, the western olivaceous warbler is larger, has a browner tinge to its upperparts, and also has a larger bill. Its song is a fast nasal babbling.
