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

Black-tailed Gnatcatcher Population Trend in Arizona

All statesArid-land birds

Black-tailed Gnatcatcher in Arizona has fallen sharply: down 52% on the route-weighted index since 1970.

-52%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 →
52Routes 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 Black-tailed Gnatcatcher Trends in ArizonaNotable 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 →

Black-tailed Gnatcatcher has fallen sharply in Arizona: down 52% on the route-weighted index since 1970.

Black-tailed Gnatcatcher Population Forecast in Arizona

If the recent trend holds, Black-tailed Gnatcatcher in Arizona is projected to rise about 103% by 2029 — from 2.3 in 2024 to a central estimate of 4.8 (95% range 0.97–8.5). A 5-year backtest shows a typical error of ±188.2%, with 60% of held-out values landing inside the 95% band.

+103%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 →
4.8Projected 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 →
0.97–8.595% 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 →
±188.2%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, Black-tailed Gnatcatcher in Arizona is projected to rise about 103% by 2029 — from 2.3 in 2024 to a central estimate of 4.8 (95% range 0.97–8.5). A 5-year backtest shows a typical error of ±188.2%, with 60% 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 →
20254.60.798.3
20264.60.838.4
20274.70.888.4
20284.70.938.5
20294.80.978.5

Black-tailed Gnatcatcher Survey Routes in Arizona

Routes recording Black-tailed Gnatcatcher in Arizona.
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 →
Cutter3720141992
Organ Pipe3520231990
New River2620161975
Cibola Lake2420241993
Bates Well2120231995
Cutter 21720182015
Carr Mtn1620241985
Red Rock1520141992
Pisinimo1119931992
Casa Grande1020221989
Cabeza Priet920241993
Alamo Res.820241992
Ajo720081968
Quartzsite620241974
Blue619741974
Sahuarita620231993
Wickenburg620222017
Willow Beach619971989
Pomerene520241968
Coolidge419751975
Lukeville419811975
Bartlett Res420241992
Redington420231993
Oatman320191988
Aztec Peak319771974

Black-tailed Gnatcatcher Population Trend in Other States

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