Arctic Warbler
Arctic Warbler has increased: up 27% on the route-weighted index since 1984.
About the Arctic Warbler
The Arctic Warbler (Phylloscopus borealis) is a North American member of the Leaf Warblers (Phylloscopidae). In this analysis it is grouped with the forest birds.
- Size
- 4–5 in long (10–13 cm) — a tiny songbird (typical for the family)
- Habitat
- Woodlands and forest edges, including wooded suburbs and parks.
- Diet
- Insects and spiders gleaned from foliage and bark, with seeds and berries in season.
- Range
- Recorded on 41 Breeding Bird Survey routes across 1 state, most concentrated in the BCR 4.
- Family
- Phylloscopidae · Forest birds
Notable Arctic Warbler Trends
No notable trend signals for Arctic Warbler. See the full index history below.
Arctic Warbler Population Forecast
If the recent trend holds, Arctic Warbler is projected to rise about 11% by 2029 — from 0.08 in 2024 to a central estimate of 0.09 (95% range 0.01–0.17). A 5-year backtest shows a typical error of ±51.6%, with 100% of held-out values landing inside the 95% band.
| Year | Projected index | 95% low | 95% high |
|---|---|---|---|
| 2025 | 0.09 | 0.01 | 0.17 |
| 2026 | 0.09 | 0.01 | 0.17 |
| 2027 | 0.09 | 0.01 | 0.17 |
| 2028 | 0.09 | 0.01 | 0.17 |
| 2029 | 0.09 | 0.01 | 0.17 |
Where the Arctic Warbler Is Detected
BBS routes recording Arctic Warbler, sized by most recent count.
Arctic Warbler Population Trend by State
| Alaska | -49% | 1984 | 41 |
Arctic Warbler Population Trend by Region
Bird Conservation Regions are the ecological unit for trends.
| BCR 2 | -36% | 1994 | 14 |
| BCR 3 | +24% | 1998 | 3 |
| BCR 4 | -56% | 1984 | 22 |
Arctic Warbler Conservation Status
Our route-weighted index shows it up about 27% since 1984.
Source: USGS North American Breeding Bird Survey, retrieved 2026-05-22. Trend is a route-weighted relative-abundance index, not an absolute population.