Phylloscopus bonelli (Vieillot, 1819)

Common and Scientific Name

Western Bonelli's warbler (scientific name Phylloscopus bonelli (Vieillot, 1819)) is a small passerine bird that inhabits forest and woodland areas.

Diet

This species is insectivorous, like most warblers.

Plumage Details

Adult western Bonelli's warblers have a plain grey-green back, green-toned rump and wings, and whitish underparts.

Morphological Features

They have a small pointed bill and brown legs.

Sexual Dimorphism

As with most warblers, the sexes are identical in appearance.

Plumage Comparison to Eastern Conspecific

Compared to eastern Bonelli's warblers, western Bonelli's warblers have a browner tinge to their upperparts; eastern Bonelli's warblers sometimes have a greenish tinge to the upperparts instead.

Song Description

The song of the western Bonelli's warbler is a fast monotone trill.

Song Similarities to Other Species

It is only slightly different from the song of the eastern Bonelli's warbler, and also shares some similarity with the song of the wood warbler.

Call Description

The call of the western Bonelli's warbler is a disyllabic hu-it.

Call Comparison to Eastern Conspecific

This differs from the call of the eastern Bonelli's warbler, which is a hard chup that resembles the calls of a crossbill or house sparrow.

Breeding Nest Location

For breeding, western Bonelli's warblers build nests on the ground.

Clutch Size Records

Original sources note conflicting clutch sizes, stating both that four to six eggs are laid, and that clutches contain 3 to 5 eggs.

Egg Appearance

The eggs are white with reddish-brown markings.

Incubation and Fledging Periods

Incubation lasts around 14 days, and the chicks fledge 10 to 14 days after hatching.

Breeding Threats

Cuckoo brood parasitism and nest predation are major threats to the breeding success of this species.