Greenish Warbler

Overview

The Greenish Warbler (Phylloscopus trochiloides) is a widespread leaf warbler and strong migrant that breeds in northeastern Europe and temperate to subtropical continental Asia before wintering in India. It is a ring species with complex population structures, including a western group known as green warblers and an eastern group.

Identification

• Plumage: Grayish-green above and off-white below; the viridanus subspecies has a dull green upper part with a yellowish supercilium, throat, and breast.
• Size: Slightly smaller than the Arctic Warbler (Phylloscopus borealis) with a thinner bill that lacks a dark tip to the lower mandible.
• Markings: A single wing bar distinguishes southern and western populations, though traces of a second wing bar may occur in eastern populations.
• Song: A high, jerky trill that may include a sequence of down-slurred and occasionally up-slurred notes; songs are generally shorter around the Himalayas.

Habitat

Breeding populations favour lowland deciduous or mixed forests, while non-breeding birds in warmer regions may move to montane habitats in summer, such as humid fir forests in Bhutan up to 3,800 meters. The species ranges across northeastern Europe and continental Asia, with vagrant birds occasionally appearing in Western Europe and Great Britain.

Diet

Like its relatives, the Greenish Warbler is a small passerine that is insectivorous. It builds its nest on the ground within low shrubs.

Did you know?

This species is a textbook example of a ring species, where populations have diverged eastwards and westwards around the Tibetan Plateau and eventually meet on the northern side, resulting in confusing taxonomic relationships and frequent hybridisation between adjacent subspecies.