The western subalpine warbler is a small typical warbler which breeds in the southernmost areas of Europe and north-western Africa. Like most Currucaspecies, it has distinct male and female plumages. The adult male has a grey back and head, brick-red underparts, and white malar streaks. The female is mainly brown above, with a greyer head, and whitish below with a pink flush. The subalpine warbler's song is fast and rattling, and is similar to the lesser whitethroat. This bird seems to be related to the Sardinian warbler–Menetries' warbler superspecies. They all have white malar areas, the heads being dark above in adult males, and naked eye-rings. These three species are related to a superspecies consisting ofRüppell's warbler and the Cyprus warbler, which also share the white malar area with blackish above. The subalpine warbler is divided into two distinct subspecies groups, which may possibly be sufficiently diverged to qualify as two separate species. The two groups have differing male plumages, distinctive calls, and are allopatric; further study is needed. In May 2020, the IOC world bird list the split of western and eastern subalpine warbler as two distinct species. This is a bird of dry open country, often on hill slopes, with bushes for nesting. The nest is built in low shrub or gorse, and 3–5 eggs are laid. Like most "warblers", it is insectivorous, but will also take berries.
This species prefers tall and dense heterogeneous maquis with sparse tree cover in dry Mediterranean areas, particularly maquis of holm oak and those dominated by strawberry tree and tree-heath. It is also frequently found in young cork oak forest and in dense but treeless bushy areas. It uses bushy formations dominated by brambles along sunny ravines and valley bottoms and prefers the intermediate stages of post-wildfire succession. Breeding occurs from late March to late June and the species is monogamous. The male constructs several ‘cock nests’ but both sexes build the breeding nest which is a deep, robust cup of grasses, thin roots and leaves and lined with finer grasses, rootlets and hair. It is placed in low scrub, bush or a small tree, c. 30–130 cm above the ground. Clutches are three to five eggs. The diet is mostly small insects and their larvae but outside of the breeding season berries and fruits are also taken. The species is a long distance migrant, wintering in sub-Saharan Africa.
