Phylloscopus borealis (J.H.Blasius, 1858)

Scientific Classification and Common Name

The Arctic warbler, with the scientific name Phylloscopus borealis, is a widespread leaf warbler that breeds in birch or mixed birch forest near water across Fennoscandia and the northern Palearctic. It has established a breeding foothold in North America in Alaska.

Migratory Behavior

This warbler is strongly migratory, and the entire population winters in southeast Asia. Because of this travel route, it has one of the longest migrations of any Old World insectivorous bird.

Taxonomic Splits

Populations that breed in Kamchatka, the Kuril Islands and Japan were traditionally included within this species, but genetic and vocal evidence strongly supported splitting these into separate species. They are now all considered distinct: the Kamchatka leaf warbler is found in Kamchatka, Hokkaido and the Kuril Islands, and the Japanese leaf warbler occurs in Japan except for Hokkaido.

Nesting Habit

The Arctic warbler builds its nest on the ground in a low shrub.

Diet

Like most Old World warblers, this small passerine bird feeds on insects.

Plumage Appearance

In appearance, it is a typical leaf warbler, with greyish-green upperparts and off-white underparts. Its single wing bar sets it apart from most similar species, with the exception of the greenish warbler, Phylloscopus trochiloides.

Morphological Comparison to Greenish Warbler

The Arctic warbler is larger than the greenish warbler, and has a heavier, dagger-like bill, with a dark tip on the lower mandible.

Vocalization

Its song is a fast trill.

Vagrant Occurrence in Western Europe

This species appears as an autumn vagrant in western Europe, and occurs annually in Great Britain. Between 1958 and 2001, there were 225 confirmed sightings of Arctic warblers in Britain.

Etymology of Genus Name

The genus name Phylloscopus comes from Ancient Greek: phullon means "leaf", and skopos means "seeker", derived from skopeo meaning "to watch".

Etymology of Specific Epithet

The specific epithet borealis comes from Latin, and means "northern".