BirdAnalyst
Species · Colorado · BBS 2025 Release · 1966–2024

Loggerhead Shrike Population Trend in Colorado

All statesGeneralists

Loggerhead Shrike in Colorado has fallen sharply: down 69% on the route-weighted index since 1970.

-69%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 →
79Routes In StateSurvey routesHow many standard-protocol BBS routes contributed counts. More routes means a steadier, better-sampled index; very thin coverage is suppressed.Full methodology →
56YearsYears surveyedNumber of years with at least one standard-protocol run in this geography. A longer record makes the trend more reliable.Full methodology →

Notable Loggerhead Shrike Trends in ColoradoNotable 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 declinecomputed 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 →

Loggerhead Shrike has fallen sharply in Colorado: down 69% on the route-weighted index since 1970.

Loggerhead Shrike Population Forecast in Colorado

If the recent trend holds, Loggerhead Shrike in Colorado is projected to fall about 34% by 2029 — from 0.65 in 2024 to a central estimate of 0.43 (95% range 0.00–1.2). A 5-year backtest shows a typical error of ±22.9%, with 100% of held-out values landing inside the 95% band.

-34%Change by 2029TrendPercent 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 →
0.43Projected 2029 indexProjected indexThe central forecast of the abundance index if the recent trend continues. A projection of the current trajectory, not a prediction.Full methodology →
0.00–1.295% 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 →
±22.9%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, Loggerhead Shrike in Colorado is projected to fall about 34% by 2029 — from 0.65 in 2024 to a central estimate of 0.43 (95% range 0.00–1.2). A 5-year backtest shows a typical error of ±22.9%, with 100% of held-out values landing inside the 95% band.19682029
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 →
20250.510.001.3
20260.490.001.3
20270.470.001.2
20280.450.001.2
20290.430.001.2

Loggerhead Shrike Survey Routes in Colorado

Routes recording Loggerhead Shrike in Colorado.
Recent countThe raw number of individuals recorded on this route in its most recent survey year. A single-route tally, not a trend.Full methodology →
Crowley1620241990
Prospect Val1420001992
Adams Co.1120221989
Bennett920181995
Rush720221983
Mica Butte719871968
Bethune720161991
Last Chance 2620242017
Waverly520181990
Doyle Bridge519971992
Basin520241995
Boyero420171979
Villegreen420241996
Briggsdale320241968
Gilpin320241971
Edison320241988
Grover320231992
Ninaview320171994
Pritchett320242000
Rockport320241995
Prospect Valley 2320232001
Doyle Bridge 2320231998
Maybell220241971
Great Divide220182010
Fruita220061988

Loggerhead Shrike Population Trend in Other States

alabamaarizonaarkansascaliforniafloridageorgiaidahoillinoisindianaiowakansaskentuckylouisianamainemarylandmichiganminnesotamississippimissourimontananebraskanevadanew-mexiconew-yorknorth-carolinanorth-dakotaohiooklahomaoregonpennsylvaniasouth-carolinasouth-dakotatennesseetexasutahvermontvirginiawashingtonwest-virginiawisconsinwyoming

Source: USGS North American Breeding Bird Survey, retrieved 2026-05-22.