BirdAnalyst
Species · BBS 2026 Release · 1966–2025

Curve-billed Thrasher Population Analysis

MimidaeArid-land birdsToxostoma curvirostre

Curve-billed Thrasher has edged down: down 21% on the route-weighted index since 1969.

-21%Since 1969TrendPercent 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 →
256RoutesSurvey routesHow many standard-protocol BBS routes contributed counts. More routes means a steadier, better-sampled index; very thin coverage is suppressed.Full methodology →
58Years 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 Curve-billed Thrasher

The Curve-billed Thrasher (Toxostoma curvirostre) is a North American member of the Mockingbirds & Thrashers (Mimidae). In this analysis it is grouped with the arid-land birds.

Size
8–12 in long (20–30 cm) — a slender, long-tailed songbird (typical for the family)
Habitat
Deserts, dry scrub and brushland of the Southwest.
Diet
Seeds, insects and cactus fruit of arid-land plants.
Range
Recorded on 256 Breeding Bird Survey routes across 7 states, most concentrated in the Shortgrass Prairie.
Family
Mimidae · Arid-land birds

Notable Curve-billed Thrasher TrendsNotable signalsLong-arc shifts the engine flags automatically — sustained declines or increases large enough to stand out from year-to-year noise.Full methodology →

No notable trend signals for Curve-billed Thrasher. See the full index history below.

Curve-billed Thrasher Population Forecast

If the recent trend holds, Curve-billed Thrasher is projected to rise about 36% by 2030 — from 0.10 in 2025 to a central estimate of 0.13 (95% range 0.05–0.21). A 5-year backtest shows a typical error of ±30.6%, with 100% of held-out values landing inside the 95% band.

+36%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 →
0.13Projected 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 →
0.05–0.2195% 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 →
±30.6%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, Curve-billed Thrasher is projected to rise about 36% by 2030 — from 0.10 in 2025 to a central estimate of 0.13 (95% range 0.05–0.21). A 5-year backtest shows a typical error of ±30.6%, with 100% of held-out values landing inside the 95% band.19672030
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 →
20260.130.050.21
20270.130.050.21
20280.130.050.21
20290.130.050.21
20300.130.050.21

Where the Curve-billed Thrasher Is Detected

BBS routes recording Curve-billed Thrasher, sized by most recent count.

Curve-billed Thrasher Population Trend by State

Curve-billed Thrasher 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+20%197055
Colorado+29%198114
Kansasinsufficient datan/a4
Nevadainsufficient datan/a1
New Mexico+83%197050
Oklahoma-5%20113
Texas-68%1969129

Curve-billed Thrasher Population Trend by Region

Bird Conservation Regions are the ecological unit for trends.

Curve-billed Thrasher 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 →
Southern Rockies / Colorado Plateau+17%197119
Shortgrass Prairie+18%197058
Central Mixed Grass Prairie+54%197518
Edwards Plateau+12%197710
Oaks and Prairies-84%197011
Sonoran and Mojave Deserts-8%197030
Sierra Madre Occidental+100%197022
Chihuahuan Desert+11%196953
Tamaulipan Brushlands-74%196927
Gulf Coastal Prairie-57%19707

Curve-billed Thrasher Conservation Status

Our route-weighted index shows it down about 21% since 1969.

Source: USGS North American Breeding Bird Survey, retrieved 2026-08-14. Trend is a route-weighted relative-abundance index, not an absolute population.