MacGillivray's Warbler
MacGillivray's Warbler has surged: up 196% on the route-weighted index since 1970.
About the MacGillivray's Warbler
The MacGillivray's Warbler (Geothlypis tolmiei) is a North American member of the Wood-Warblers (Parulidae). In this analysis it is grouped with the forest birds.
- Size
- 4.5–5.5 in long (11–14 cm) — a small, active 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 621 Breeding Bird Survey routes across 14 states, most concentrated in the Northern Rockies.
- Family
- Parulidae · Forest birds
Notable MacGillivray's Warbler Trends
MacGillivray's Warbler has surged in surveyed states: up 196% on the route-weighted index since 1970.
MacGillivray's Warbler Population Forecast
If the recent trend holds, MacGillivray's Warbler is projected to rise about 42% by 2029 — from 0.48 in 2024 to a central estimate of 0.69 (95% range 0.50–0.88). A 5-year backtest shows a typical error of ±54.1%, with 0% of held-out values landing inside the 95% band.
| Year | Projected index | 95% low | 95% high |
|---|---|---|---|
| 2025 | 0.66 | 0.47 | 0.85 |
| 2026 | 0.67 | 0.48 | 0.85 |
| 2027 | 0.67 | 0.48 | 0.86 |
| 2028 | 0.68 | 0.49 | 0.87 |
| 2029 | 0.69 | 0.50 | 0.88 |
Where the MacGillivray's Warbler Is Detected
BBS routes recording MacGillivray's Warbler, sized by most recent count.
MacGillivray's Warbler Population Trend by State
| Alaska | -92% | 1986 | 16 |
| Arizona | insufficient data | n/a | 4 |
| California | +219% | 1971 | 114 |
| Colorado | +8% | 1970 | 80 |
| Idaho | +96% | 1973 | 47 |
| Montana | +101% | 1970 | 47 |
| Nevada | -50% | 1993 | 13 |
| New Mexico | -29% | 1970 | 14 |
| Oregon | -17% | 1970 | 102 |
| South Dakota | +2% | 1993 | 10 |
| Texas | insufficient data | n/a | 1 |
| Utah | +346% | 1970 | 51 |
| Washington | -27% | 1970 | 79 |
| Wyoming | +110% | 1970 | 43 |
MacGillivray's Warbler Population Trend by Region
Bird Conservation Regions are the ecological unit for trends.
| Northern Pacific Rainforest | -47% | 1970 | 132 |
| Great Basin | +33% | 1970 | 109 |
| Northern Rockies | +55% | 1970 | 152 |
| Sierra Nevada | -8% | 1972 | 36 |
| Southern Rockies / Colorado Plateau | +82% | 1970 | 138 |
| Badlands and Prairies | +204% | 1978 | 17 |
| Coastal California | -42% | 1973 | 29 |
| Sierra Madre Occidental | +27% | 1998 | 4 |
MacGillivray's Warbler Conservation Status
Our route-weighted index shows it up about 196% since 1970.
Source: USGS North American Breeding Bird Survey, retrieved 2026-05-22. Trend is a route-weighted relative-abundance index, not an absolute population.