Afghanistan (B), Austria, Azerbaijan (B) (NB), Bangladesh, Belarus (B), Bhutan (B), Cambodia, China (mainland) (B), Czech Republic (B), Denmark (B) (P), Estonia (B), Finland (B), Germany (B), India (B), Iran [Islamic Republic of] (B), Kazakhstan (B), Kuwait (P), Kyrgyzstan (B), Laos, Latvia (B), Lithuania (B), Mongolia (B), Myanmar, Nepal (B), North Korea, Norway (B), Pakistan, Poland (B), Russia (Asian) (B), Russia (Central Asian) (B), Russia (European) (B), Slovakia (Slovak Republic) (B), South Korea, Sweden (B), Tajikistan (B), Thailand, Turkey (B), Ukraine (B), Uzbekistan (B), Vietnam.
Vagrant to Bahrain, Belgium, Faroe Islands, France, Greece, Hong Kong (China), Ireland, Italy, Malaysia, Netherlands Antilles, Oman, Romania, Spain, United Arab Emirates, United Kingdom.
Population
Estimated population is 150,000,000 - 1,000,000,000 (2010).
Subspecies
Taxonomic position uncertain. Frequently considered conspecific with Green Warbler (Phylloscopus nitidus), but evidence from mitochondrial DNA indicates that the two are intermediate between species and subspecies in terms of the degree of divergence between them. Often treated as conspecific with Phylloscopus plumbeitarsus, but mitochondrial DNA also indicates genetic split between that species and subspecies viridanus of present species. In addition, playback experiments revealed that these two taxa do not recognize each other's songs, and in the region of geographical overlap in central Siberia they behave as separate species. Possible hybridization with Willow Warbler (Phylloscopus trochilus) recorded.
The following 4 subspecies are recognised:
viridanus Blyth, 1843 - Breeds east-central and north-eastern Europe east to central Siberia, south to Pamir Mts, north-western China (western Xinjiang) and north-western Mongolia. Non-breeding Pakistan, Nepal, India and Sri Lanka.
ludlowi Whistler, 1931 - Breeds northern Afghanistan, northern Pakistan and Kashmir eastern in north-western Himalayas to northern India (east to Kumaon). Non-breeding east-central India (Andhra Pradesh).
trochiloides (Sundevall, 1837) - Breeds central and eastern Himalayas from north-western India (Punjab) east to southern and central China (south-eastern Xizang east to eastern and southern Sichuan and north-western Yunnan). Non-breeding north-eastern India, Bangladesh, southern China (south-eastern Xizang, southern Yunnan), Myanmar, western and northern Thailand, northern Laos and northern Vietnam (Tonkin).
obscuratus Stresemann, 1929 - Breeds central China (eastern Qinghai and eastern and southern Xizang east to Gansu and Sichuan). Non-breeding southern China (south-western Yunnan, Hainan), Myanmar, north-western Thailand and northern Indochina.
The Reader's Digest Book of British Birds 1980, 3rd Edition, Drive Publications Ltd ISBN 0 340 25308 8
Birds in Colour Campbell, B., 1960, Penguin Books Ltd
The Pocket Guide to Nest and Eggs Fitter, R.S.R., 1954, Collins
RSPB Handbook of British Birds Holden, P., Cleeves, T., 2002, A & C Black ISBN 0 7136 5713 8
Birds of Britain and Europe Sterry, P., et al., 2001, AA Publishing ISBN 0 7495 3068 5
The Popular Handbook of British Birds Hollom, P.A.D., 1973, H.F. & G. Witherby Ltd ISBN 0 85493 002 7