Phylloscopus sibilatrix is a widespread summer visitor to much of Europe, which constitutes >75% of its global breeding range. Its European breeding population is extremely large (>14,000,000 pairs), and was stable between 1970-1990. Although most populations in eastern Europe remained stable during 1990-2000 (the trend of the key population in Russia was unknown), the species declined in the north and west, and underwent a moderate decline (>10%) overall. Consequently, this previously Secure species is now provisionally evaluated as Declining.

Breeds in temperate and boreal west Palearctic in middle and upper middle latitudes. Largely in continental but marginally in oceanic climates, preferring hilly terrain to flat plains. Breeds regularly in Alps up to 1300 m, and exceptionally rather higher. Requires moist and shady woods with closed canopy and no or sparse undergrowth, being a typical bird of wood of beech, but often found also in mixed oak and hornbeam, sweet chestnut,spruce and mixed woodlands.

Breeds May to mid June in western and central Europe, last third May to early July in Finland. Nest site is built on ground in vegetation, sometimes wedged under fallen tree or branch. Often in slight depression usually made by bird. Nest, domed structure of dry grass leaves and stems and other plant material, including bark, lined with finer grasses and hair. 5-7 eggs are laid, incubation 12-14 days, by female only.

Mainly insects and other invertebrates, with some fruit and seeds in autumn. Picks items off leaves and other parts of trees and bushes while moving through foliage, sometimes fluttering, frequently hovering, or by making longer flycatching sallies.

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 28,000,000-43,000,000 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.

All populations migratory, wintering in sub-Saharan Africa from Sierra Leone and southern Guinea east to extreme south of Sudan and western Uganda, south to c. 6°S in Zaïre. In autumn, large numbers pass through central Mediterranean (Italy to Aegean), and highest concentrations winter immediately south of this region; passage regular in smaller numbers in east Mediterranean and Levant, and infrequent in west Mediterranean. Northward movement in spring follows similar course, but relatively more birds cross west Mediterranean. Movement is rapid in both seasons. Autumn migration begins mid-July, with main departure of European breeders in August; last records (including passage birds) in western and central Europe mostly early or mid-September. Spring migration begins in March, chiefly April to mid-May. Recorded until April throughout winter range. Passage across Mediterranean late March to late May, chiefly in 2nd half of April. Movement through Europe is apparently in successive waves, with southern breeding grounds re-occupied first. Reaches western and central Europe mid- to late April, further north and east mostly in May.

article number 1 Title
Genetically confirmed interbreeding between western Bonelli's warbler ( Phylloscopus bonelli ) and wood warbler ( P. sibilatrix )
Author(s): Christian Dietzen, Clemens Hackenberg et al
Abstract: During May and June 2003, a mixed breeding pair consisting of a male western Bonelli's warbler (Phylloscopus bonelli) and a female wood warbler (P. sibilatrix) successfully raised six young in a broad..[more]..
Source: J Ornithol (2007) 148:8590
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