Cassin's Kingbird
Cassin's Kingbird has risen sharply: up 72% on the route-weighted index since 1970.
About the Cassin's Kingbird
The Cassin's Kingbird (Tyrannus vociferans) is a North American member of the Tyrant Flycatchers (Tyrannidae). In this analysis it is grouped with the aerial insectivores.
- Size
- 4.5–9 in long (12–23 cm) — a small to medium flycatcher (typical for the family)
- Habitat
- Open airspace over fields, water and towns; nests in cavities, earthen banks or on structures.
- Diet
- Flying insects caught on the wing.
- Range
- Recorded on 320 Breeding Bird Survey routes across 13 states, most concentrated in the Southern Rockies / Colorado Plateau.
- Family
- Tyrannidae · Aerial insectivores
Notable Cassin's Kingbird Trends
Cassin's Kingbird has risen sharply in surveyed states: up 72% on the route-weighted index since 1970.
Cassin's Kingbird Population Forecast
If the recent trend holds, Cassin's Kingbird is projected to rise about 12% by 2029 — from 0.31 in 2024 to a central estimate of 0.34 (95% range 0.26–0.43). A 5-year backtest shows a typical error of ±24.5%, with 80% of held-out values landing inside the 95% band.
| Year | Projected index | 95% low | 95% high |
|---|---|---|---|
| 2025 | 0.33 | 0.25 | 0.42 |
| 2026 | 0.34 | 0.25 | 0.42 |
| 2027 | 0.34 | 0.25 | 0.42 |
| 2028 | 0.34 | 0.26 | 0.43 |
| 2029 | 0.34 | 0.26 | 0.43 |
Where the Cassin's Kingbird Is Detected
BBS routes recording Cassin's Kingbird, sized by most recent count.
Cassin's Kingbird Population Trend by State
| Arizona | -12% | 1970 | 62 |
| California | +223% | 1971 | 49 |
| Colorado | -8% | 1972 | 46 |
| Kansas | insufficient data | n/a | 3 |
| Montana | -66% | 1981 | 5 |
| Nebraska | insufficient data | n/a | 2 |
| Nevada | insufficient data | n/a | 3 |
| New Mexico | +2% | 1970 | 71 |
| Oklahoma | insufficient data | n/a | 1 |
| South Dakota | insufficient data | n/a | 1 |
| Texas | -39% | 1970 | 35 |
| Utah | +16% | 1988 | 25 |
| Wyoming | +2% | 1980 | 17 |
Cassin's Kingbird Population Trend by Region
Bird Conservation Regions are the ecological unit for trends.
| Great Basin | -21% | 1990 | 4 |
| Southern Rockies / Colorado Plateau | -19% | 1970 | 100 |
| Badlands and Prairies | +80% | 1979 | 18 |
| Shortgrass Prairie | +103% | 1970 | 49 |
| Coastal California | +268% | 1971 | 36 |
| Sonoran and Mojave Deserts | -34% | 1970 | 25 |
| Sierra Madre Occidental | -35% | 1970 | 35 |
| Chihuahuan Desert | -54% | 1970 | 45 |
Cassin's Kingbird Conservation Status
Our route-weighted index shows it up about 72% since 1970. Aerial insectivores have fallen sharply across the continent, a decline widely linked to dwindling insect prey.
Source: USGS North American Breeding Bird Survey, retrieved 2026-05-22. Trend is a route-weighted relative-abundance index, not an absolute population.