Guide to North American Birds

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Adult. Photo: Daniel Behm

Arctic Warbler

Phylloscopus borealis

Along willow-lined streams in Alaska in summer, the song of the Arctic Warbler is unmistakable: a slow trill, with an insistent or hammering sound. When the bird hops into view among the branches, it is less distinctive, plain olive and whitish with a pale eyebrow. In fall, the Arctic Warbler crosses the Bering Strait and migrates south in Asia.

Conservation status	The small population in Alaska is probably stable; could be affected by loss of habitat on wintering grounds.
Family	Leaf-Warblers
Habitat	Willow scrub. In Alaska, breeds in dense low thickets (4-10' tall) of willow, dwarf birch, or alder, mainly along streams. In Eurasia, breeds in similar habitat, but also in open forest of conifers mixed with deciduous shrubs.

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Feeding Behavior

Forages very actively among the foliage of bushes and trees, examining twigs and leaves for insects. Sometimes hovers to glean insects from foliage. Flies out to catch insects in mid-air, and may do so repeatedly when midges or mayflies are swarming.

Eggs

6-7, sometimes 5. White, finely dotted with brown. Incubation is by female only, 11-13 days. Young: Both parents feed nestlings. Young leave nest about 12-14 days after hatching. 1 brood per year.

Young

Both parents feed nestlings. Young leave nest about 12-14 days after hatching. 1 brood per year.

Diet

Mostly insects. Diet in North America is not well known. In Eurasia, feeds on a wide variety of insects, especially beetles, mosquitoes, flies, leafhoppers, caterpillars, true bugs, mayflies, sawflies, also many others. Also eats some spiders and snails.

Nesting

Nesting behavior in Alaska not well known; information here includes data from Eurasia. Male sings to defend nesting territory; in aggressive encounters between males, they may flap wings slowly while singing. Nest site is on ground, usually in mossy ground cover under dense shrubs or in crevice among roots, sometimes tucked into side of grass tussock. Typically well hidden. Nest (thought to be built by female) is a domed structure with the entrance on the side; made of grass, weeds, moss, leaves, lined with fine grass.

Illustration © David Allen Sibley.
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Text © Kenn Kaufman, adapted from
Lives of North American Birds

Migration

Alaskan birds winter especially in the Philippines, also in nearby areas of southeast Asia and Indonesia. Unlike some other Alaskan breeders, this species almost never strays southward in the New World.

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Migration

All Seasons - Common
All Seasons - Uncommon
Breeding - Common
Breeding - Uncommon
Winter - Common
Winter - Uncommon
Migration - Common
Migration - Uncommon

Songs and Calls

A quick trill, introduced by zick or zick-zick-zick. The call is also zick or zirrup.

Audio © Lang Elliott, Bob McGuire, Kevin Colver, Martyn Stewart and others.
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How Climate Change Will Reshape the Range of the Arctic Warbler

Audubon’s scientists have used 140 million bird observations and sophisticated climate models to project how climate change will affect this bird’s range in the future.

Zoom in to see how this species’s current range will shift, expand, and contract under increased global temperatures.

Climate threats facing the Arctic Warbler

Choose a temperature scenario below to see which threats will affect this species as warming increases. The same climate change-driven threats that put birds at risk will affect other wildlife and people, too.