Worm-eating Warbler
Worm-eating Warbler has surged: up 104% on the route-weighted index since 1968.
About the Worm-eating Warbler
The Worm-eating Warbler (Helmitheros vermivorum) 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 797 Breeding Bird Survey routes across 28 states, most concentrated in the Appalachian Mountains.
- Family
- Parulidae · Forest birds
Notable Worm-eating Warbler Trends
Worm-eating Warbler has surged in surveyed states: up 104% on the route-weighted index since 1968.
Worm-eating Warbler Population Forecast
If the recent trend holds, Worm-eating Warbler is projected to rise about 37% by 2029 — from 0.18 in 2024 to a central estimate of 0.25 (95% range 0.18–0.32). A 5-year backtest shows a typical error of ±23.5%, with 80% of held-out values landing inside the 95% band.
| Year | Projected index | 95% low | 95% high |
|---|---|---|---|
| 2025 | 0.24 | 0.17 | 0.31 |
| 2026 | 0.24 | 0.17 | 0.31 |
| 2027 | 0.24 | 0.17 | 0.31 |
| 2028 | 0.25 | 0.18 | 0.32 |
| 2029 | 0.25 | 0.18 | 0.32 |
Where the Worm-eating Warbler Is Detected
BBS routes recording Worm-eating Warbler, sized by most recent count.
Worm-eating Warbler Population Trend by State
| Alabama | +346% | 1968 | 61 |
| Arkansas | -30% | 1969 | 33 |
| Connecticut | +568% | 1972 | 17 |
| Delaware | +442% | 1971 | 13 |
| Georgia | -13% | 1975 | 16 |
| Illinois | +63% | 1983 | 12 |
| Indiana | +90% | 1973 | 12 |
| Iowa | insufficient data | n/a | 1 |
| Kentucky | +69% | 1968 | 43 |
| Louisiana | +227% | 1969 | 30 |
| Maryland | +699% | 1968 | 64 |
| Massachusetts | +93% | 1992 | 5 |
| Mississippi | +194% | 1976 | 32 |
| Missouri | +204% | 1976 | 36 |
| New Hampshire | insufficient data | n/a | 1 |
| New Jersey | +313% | 1979 | 22 |
| New York | -25% | 1970 | 24 |
| North Carolina | +129% | 1971 | 59 |
| Ohio | 21× | 1980 | 24 |
| Oklahoma | -7% | 1972 | 9 |
| Pennsylvania | +142% | 1968 | 86 |
| Rhode Island | +233% | 1992 | 3 |
| South Carolina | -47% | 1996 | 8 |
| Tennessee | +146% | 1968 | 40 |
| Texas | -2% | 1978 | 12 |
| Virginia | +408% | 1968 | 72 |
| West Virginia | -38% | 1968 | 61 |
| Wisconsin | insufficient data | n/a | 1 |
Worm-eating Warbler Population Trend by Region
Bird Conservation Regions are the ecological unit for trends.
| Lower Great Lakes / St. Lawrence Plain | +0% | 1970 | 7 |
| Atlantic Northern Forest | +1% | 1981 | 9 |
| Eastern Tallgrass Prairie | -1% | 1982 | 18 |
| Central Hardwoods | +150% | 1968 | 100 |
| West Gulf Coastal Plain / Ouachitas | -27% | 1969 | 65 |
| Mississippi Alluvial Valley | -2% | 1978 | 7 |
| Southeastern Coastal Plain | +775% | 1969 | 115 |
| Appalachian Mountains | +213% | 1968 | 310 |
| Piedmont | +111% | 1969 | 65 |
| New England / Mid-Atlantic Coast | +547% | 1968 | 97 |
Worm-eating Warbler Conservation Status
Our route-weighted index shows it up about 104% since 1968.
Source: USGS North American Breeding Bird Survey, retrieved 2026-05-22. Trend is a route-weighted relative-abundance index, not an absolute population.