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Species · Arizona · BBS 2025 Release · 1966–2024

Northern Beardless-Tyrannulet Population Trend in Arizona

All statesAerial insectivores

Northern Beardless-Tyrannulet in Arizona has declined: down 45% on the route-weighted index since 1971.

-45%Since 1971TrendPercent 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 →
6Routes 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 →
49YearsYears surveyedNumber of years with at least one standard-protocol run in this geography. A longer record makes the trend more reliable.Full methodology →

Notable Northern Beardless-Tyrannulet 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 →

No notable trend signals for Northern Beardless-Tyrannulet in Arizona. See the full index history below.

Northern Beardless-Tyrannulet Population Forecast in Arizona

If the recent trend holds, Northern Beardless-Tyrannulet in Arizona is projected to fall about 31% by 2029 — from 0.14 in 2024 to a central estimate of 0.10 (95% range 0.00–0.23). A 5-year backtest shows a typical error of ±22.4%, with 100% of held-out values landing inside the 95% band.

-31%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 →
0.10Projected 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 →
0.00–0.2395% 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 →
±22.4%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, Northern Beardless-Tyrannulet in Arizona is projected to fall about 31% by 2029 — from 0.14 in 2024 to a central estimate of 0.10 (95% range 0.00–0.23). A 5-year backtest shows a typical error of ±22.4%, with 100% of held-out values landing inside the 95% band.19692029
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 →
20250.100.000.23
20260.100.000.23
20270.100.000.23
20280.100.000.23
20290.100.000.23

Northern Beardless-Tyrannulet Survey Routes in Arizona

Routes recording Northern Beardless-Tyrannulet 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 →
Sahuarita320191992
Pomerene320241969
Patagonia120241969
Redington120211993
Amado120221993
Peña Blanca120241985

Northern Beardless-Tyrannulet Population Trend in Other States

texas

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