Greenish Warbler (Phylloscopus trochiloides) and Green Warbler (Phylloscopus nitidus) are two very similar species that are often considered flagbearers of migration within the Indian Subcontinent.
Greenish Warbler has a widespread breeding range spanning many subspecies and the entire breadth of temperate Eurasia including the Himalayas. Almost the entire global population of the western subspecies viridanus winters in the Indian peninsula and Sri Lanka. Greenish Warbler joins Common Rosefinch, Blyth’s Reed Warbler, Booted Warbler, Red-breasted Flycatcher and Bluethroat whose European populations (including Western Europe) winter almost entirely in the Indian Subcontinent!
Subspecies trochiloides/ludlowi of Greenish Warbler that breeds in the high Himalayas and Central Asia migrates to Northeast India, Bangladesh and Southeast Asia where viridanus rarely ventures.
Green Warbler breeds in southeastern Europe and western Asia near the Caspian Sea. It winters almost entirely in peninsular India and Sri Lanka, primarily along the west coast and in South India where both Greenish and Green Warbler often co-occur at high densities.