Small, slight, graceful warbler, light on the wing and active in cover. Epitome of Phylloscopus, particularly of small species which lack wing-bars and striking supercilium. Plumage usually quite pale and bright, with essentially olive upperparts and yillow-white underparts, yellow-white supercilium, and yellow-brown legs. Song distinctive. Sexes similar, no marked seasonal variation.
Breeds in west Palearctic in middle and upper latitudes within temperate and boreal climatic zones, continental and oceanic. Differs in being a bird less of mature woodland than of scrub, second growth, and transitions to more open habitats. Unlike P. collybita, will readily settle on shrubby, bushy, to cleared ground starting regrowth, even in absence of trees. Thus attracted to fringe areas such as birches beyond arctic taiga, heath lands, or forest clearings.
Phylloscopus trochilus is a widespread summer visitor to much of Europe (except the south), which accounts for less than half of its global breeding range. Its European breeding population is extremely large (>56,000,000 pairs), and was stable between 1970-1990. Although there were declines in a number of countries—notably Sweden and Finland—during 1990-2000, populations were stable in Russia and across much of central and eastern Europe, and the species underwent only a small decline overall.
Insects and spiders, in autumn also berries. Food obtained mostly by picking from leaves, twigs, and branches, also flycatching
This species has a large range, with an estimated global Extent of Occurrence of 10,000,000 km². It has a large global population, including an estimated 110,000,000-200,000,000 individuals in Europe (BirdLife International in prep.). Global population trends have not been quantified, but the species is not believed to approach the thresholds for the population decline criterion of the IUCN Red List (i.e. declining more than 30% in ten years or three generations). For these reasons, the species is evaluated as Least Concern. [conservation status from birdlife.org]
Breeds mid April to mid June in Central and West Europe, May-July in Finland, May to mid July in North-West European Russia. Nest site is built on ground, well concealed in vegetation, including herbs, bases of low shrubs and trees, and grass tussocks. Nest is a domed structure of dry grass, leaves, stems, moss, lichen, twigs, conifer needles, bark fibre, often with rootlets and pieces of rotten wood, lined with finer grasses, rootlets, andimal hair, and feathers. 4-8 eggs are laid, incubation, 12-14 days, by female only.
All populations migratory, wintering extensively in sub-Saharan Africa from southern Sénégal east to Ethiopia, south to South Africa. From extreme east of breeding range, route thus exceptionally long¾at least 12 000 km. Within Europe, birds from west of range head south to south-west in autumn; north Scandinavian and Finnish birds head south to south-east, indicating migratory divide in border area. Spring passage apparently on broader front, with recoveries of ringed birds averaging further east than in autumn. Afrotropical recoveries show that birds from west and central Europe, including Norway and southern Sweden, winter mainly in West Africa, birds from northern Scandinavia and Finland winter in central, East, and southern Africa. Migration earlier in autumn and later in spring than in Chiffchaff. Southward movement begins late July, and passage through Europe and across Mediterranean mostly completed by end of September. Reaches northern parts of African winter quarters in September, South Africa mostly from mid-October. Spring migration begins late February to March. Passage through Mediterranean mid-March to mid- or late May, chiefly April, averaging later in east than west. First arrivals in Britain late March, main arrival in April. Central European breeding grounds also re-occupied at end of March and in April. Main arrival in southern and central Sweden 21 April to 15 May, northern Sweden 11-25 May. At Lake Ladoga (north-west Russia), most local birds arrive by 15-20 May, passage continuing to early or mid-June.