Black-throated Blue Warbler
Black-throated Blue Warbler has surged: up 130% on the route-weighted index since 1968.
About the Black-throated Blue Warbler
The Black-throated Blue Warbler (Setophaga caerulescens) 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 485 Breeding Bird Survey routes across 18 states, most concentrated in the Appalachian Mountains.
- Family
- Parulidae · Forest birds
Notable Black-throated Blue Warbler Trends
Black-throated Blue Warbler has surged in surveyed states: up 130% on the route-weighted index since 1968.
Black-throated Blue Warbler Population Forecast
If the recent trend holds, Black-throated Blue Warbler is projected to rise about 35% by 2029 — from 0.22 in 2024 to a central estimate of 0.29 (95% range 0.23–0.36). A 5-year backtest shows a typical error of ±25.4%, with 60% of held-out values landing inside the 95% band.
| Year | Projected index | 95% low | 95% high |
|---|---|---|---|
| 2025 | 0.28 | 0.22 | 0.35 |
| 2026 | 0.28 | 0.22 | 0.35 |
| 2027 | 0.29 | 0.22 | 0.35 |
| 2028 | 0.29 | 0.22 | 0.35 |
| 2029 | 0.29 | 0.23 | 0.36 |
Where the Black-throated Blue Warbler Is Detected
BBS routes recording Black-throated Blue Warbler, sized by most recent count.
Black-throated Blue Warbler Population Trend by State
| Connecticut | +13% | 1969 | 15 |
| Georgia | insufficient data | n/a | 2 |
| Maine | +96% | 1969 | 75 |
| Maryland | +578% | 1968 | 9 |
| Massachusetts | +49% | 1969 | 17 |
| Michigan | +668% | 1973 | 49 |
| Minnesota | +359% | 1972 | 15 |
| New Hampshire | +231% | 1968 | 26 |
| New Jersey | insufficient data | n/a | 2 |
| New York | -13% | 1968 | 82 |
| North Carolina | 13× | 1970 | 22 |
| Pennsylvania | 18× | 1968 | 74 |
| Rhode Island | insufficient data | n/a | 1 |
| Tennessee | +705% | 1968 | 5 |
| Vermont | +349% | 1968 | 25 |
| Virginia | +99% | 1968 | 20 |
| West Virginia | 15× | 1970 | 25 |
| Wisconsin | +502% | 1975 | 21 |
Black-throated Blue Warbler Population Trend by Region
Bird Conservation Regions are the ecological unit for trends.
| Boreal Hardwood Transition | +944% | 1971 | 79 |
| Lower Great Lakes / St. Lawrence Plain | -60% | 1969 | 30 |
| Atlantic Northern Forest | +134% | 1968 | 155 |
| Appalachian Mountains | +799% | 1968 | 183 |
| New England / Mid-Atlantic Coast | +42% | 1968 | 28 |
Black-throated Blue Warbler Conservation Status
Our route-weighted index shows it up about 130% 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.