BirdAnalyst
Species · BBS 2026 Release · 1966–2025

Cassin's Kingbird Population Analysis

TyrannidaeAerial insectivoresTyrannus vociferans

Cassin's Kingbird has surged: up 83% on the route-weighted index since 1970.

+83%Since 1970TrendPercent change in the route-weighted abundance index between a smoothed baseline window and the most recent one. It tracks direction, not absolute population.Full methodology →
326RoutesSurvey routesHow many standard-protocol BBS routes contributed counts. More routes means a steadier, better-sampled index; very thin coverage is suppressed.Full methodology →
57Years SurveyedYears surveyedNumber of years with at least one standard-protocol run in this geography. A longer record makes the trend more reliable.Full methodology →

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 326 Breeding Bird Survey routes across 13 states, most concentrated in the Southern Rockies / Colorado Plateau.
Family
Tyrannidae · Aerial insectivores

Notable Cassin's Kingbird TrendsNotable signalsLong-arc shifts the engine flags automatically — sustained declines or increases large enough to stand out from year-to-year noise.Full methodology →

long arc increasecomputed indexTrend sourceWhether the figure is our own computed route-weighted index or an official USGS modeled estimate. The current build labels every trend as computed.Full methodology →

Cassin's Kingbird has surged in surveyed states: up 83% on the route-weighted index since 1970.

Cassin's Kingbird Population Forecast

If the recent trend holds, Cassin's Kingbird is projected to stay roughly flat through 2030, near 0.35 (95% range 0.26–0.43). A 5-year backtest shows a typical error of ±18.4%, with 100% of held-out values landing inside the 95% band.

+1%Change by 2030TrendPercent change in the route-weighted abundance index between a smoothed baseline window and the most recent one. It tracks direction, not absolute population.Full methodology →
0.35Projected 2030 indexProjected indexThe central forecast of the abundance index if the recent trend continues. A projection of the current trajectory, not a prediction.Full methodology →
0.26–0.4395% range95% rangeThe 95% uncertainty band around the projection at the forecast horizon. The true value should land inside it most of the time.Full methodology →
±18.4%Backtest errorBacktest errorTypical error when we hold out the most recent years, forecast them, and compare to what actually happened. Lower means a more trustworthy projection.Full methodology →
If the recent trend holds, Cassin's Kingbird is projected to stay roughly flat through 2030, near 0.35 (95% range 0.26–0.43). A 5-year backtest shows a typical error of ±18.4%, with 100% of held-out values landing inside the 95% band.19682030
Projection of the recent trend (dashed) with 80/95% bands — a projection, not a prediction. Habitat, climate, and land use are not modeled.
YearProjected indexProjected indexThe central forecast of the abundance index if the recent trend continues. A projection of the current trajectory, not a prediction.Full methodology →95% low95% rangeThe 95% uncertainty band around the projection at the forecast horizon. The true value should land inside it most of the time.Full methodology →95% high95% rangeThe 95% uncertainty band around the projection at the forecast horizon. The true value should land inside it most of the time.Full methodology →
20260.340.250.42
20270.340.250.42
20280.340.260.43
20290.340.260.43
20300.350.260.43

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

Cassin's Kingbird population trend by state.
TrendPercent change in the route-weighted abundance index between a smoothed baseline window and the most recent one. It tracks direction, not absolute population.Full methodology →Baseline yearThe first year of the smoothed window the trend is measured from. An earlier baseline means a longer record stands behind the number.Full methodology →Survey routesHow many standard-protocol BBS routes contributed counts. More routes means a steadier, better-sampled index; very thin coverage is suppressed.Full methodology →
Arizona-2%197063
California+225%197149
Colorado+13%197247
Kansasinsufficient datan/a3
Montana-41%19816
Nebraskainsufficient datan/a3
Nevadainsufficient datan/a3
New Mexico-2%197071
Oklahomainsufficient datan/a1
South Dakotainsufficient datan/a1
Texas-35%197036
Utah+30%198825
Wyoming+25%198018

Cassin's Kingbird Population Trend by Region

Bird Conservation Regions are the ecological unit for trends.

Cassin's Kingbird population trend by Bird Conservation Region.
TrendPercent change in the route-weighted abundance index between a smoothed baseline window and the most recent one. It tracks direction, not absolute population.Full methodology →Baseline yearThe first year of the smoothed window the trend is measured from. An earlier baseline means a longer record stands behind the number.Full methodology →Survey routesHow many standard-protocol BBS routes contributed counts. More routes means a steadier, better-sampled index; very thin coverage is suppressed.Full methodology →
Great Basin-21%19904
Southern Rockies / Colorado Plateau-20%1970100
Badlands and Prairies+141%197919
Shortgrass Prairie+163%197052
Coastal California+296%197136
Sonoran and Mojave Deserts-34%197025
Sierra Madre Occidental-34%197036
Chihuahuan Desert-56%197046

Cassin's Kingbird Conservation Status

Our route-weighted index shows it up about 83% 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 2026-08-14. Trend is a route-weighted relative-abundance index, not an absolute population.