The western olivaceous warbler, also known as isabelline warbler, is a "warbler", formerly placed in the Old World warblers when these were a paraphyletic wastebin taxon. It is now considered a member of the acrocephaline warblers, Acrocephalidae, in the tree warbler genus Iduna. It was formerly regarded as part of a wider "olivaceous warbler" species, but as a result of modern taxonomic developments, this species is now usually considered distinct from the eastern olivaceous warbler, Iduna pallida.
Region
Western Mediterranean
Typical Environment
Breeds in the Iberian Peninsula and northwest Africa, especially Morocco, Algeria, and Tunisia, in warm lowlands and river valleys. It uses riparian thickets, tamarisk stands, oleander hedges, reed-fringes, and traditional olive and citrus groves. After breeding it migrates to winter in the western Sahel from Senegal east to around Chad. During migration it occurs in a variety of scrub and farm-edge habitats.
Altitude Range
0–1500 m
Climate Zone
Subtropical
Ease of Keeping
Beginner friendly: 1/5
Also called the isabelline warbler, this species was split from the eastern olivaceous warbler based on differences in plumage, song, and genetics. It favors warm, open habitats with scattered shrubs and tall herbs, often near water or in traditional orchards. Its song is a dry, chattering warble delivered from exposed perches. Subtle field marks include warmer sandy-brown tones and a relatively long, fine bill.
Eggs, Collection Museum Wiesbaden
Temperament
shy but active
Flight Pattern
short rapid wingbeats with low, undulating flights between cover
Social Behavior
Territorial in the breeding season, typically forming monogamous pairs that nest low in shrubs or tall herbs. The cup nest is woven from grasses and plant fibers, with clutches of 3–5 eggs. Outside breeding, it forages singly or in loose associations, sometimes joining mixed-species flocks in winter quarters.
Migratory Pattern
Seasonal migrant
Song Description
A dry, chattering warble of repeated phrases with rattling and scratchy notes, delivered at a steady pace. Less melodious and more mechanical than many Hippolais warblers, often given from a prominent perch. Calls include a soft tack and harsher scolds when alarmed.
Plumage
Warm sandy-brown upperparts with a slight olive tinge, pale buff underparts shading to whitish on the throat and belly, and a diffuse pale supercilium.
Diet
Primarily small insects and other arthropods such as beetles, flies, caterpillars, aphids, and spiders. It gleans prey from leaves and twigs, hover-gleans at foliage edges, and occasionally sallies to catch flying insects. Berries and other soft plant matter are taken opportunistically, especially late in the season.
Preferred Environment
Feeds in riparian shrubs, tamarisk and oleander thickets, edges of reedbeds, and open orchards with scattered trees. Often forages from mid-level perches up to the canopy, working methodically through cover.
