BirdAnalyst
Species · Iowa · BBS 2026 Release · 1966–2025

Scarlet Tanager Population Trend in Iowa

All statesForest birds

Scarlet Tanager in Iowa has edged down: down 17% on the route-weighted index since 1976.

-17%Since 1976TrendPercent 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 →
21Routes 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 →
39YearsYears surveyedNumber of years with at least one standard-protocol run in this geography. A longer record makes the trend more reliable.Full methodology →

Notable Scarlet Tanager Trends in IowaNotable 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 Scarlet Tanager in Iowa. See the full index history below.

Scarlet Tanager Population Forecast in Iowa

If the recent trend holds, Scarlet Tanager in Iowa is projected to stay roughly flat through 2030, near 0.09 (95% range 0.00–0.22). A 5-year backtest shows a typical error of ±66.4%, with 80% of held-out values landing inside the 95% band.

n/aChange 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 →
0.09Projected 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 →
0.00–0.2295% 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 →
±66.4%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, Scarlet Tanager in Iowa is projected to stay roughly flat through 2030, near 0.09 (95% range 0.00–0.22). A 5-year backtest shows a typical error of ±66.4%, with 80% 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 →
20260.090.000.22
20270.090.000.22
20280.090.000.22
20290.090.000.22
20300.090.000.22

Scarlet Tanager Survey Routes in Iowa

Routes recording Scarlet Tanager in Iowa.
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 →
Mt Hamill120241976
Exline120181990
Bedford120121979
West Liberty120182014
Brooklyn120221987
Williamsburg120171967
Red Rock120221988
Panther120012001
Washington120212021
Wales120021972
Maquoketa120241977
Alice119781978
Dinsdale119901990
Scranton120252025
Clare120002000
Washta120101982
Sioux City119851985
Festina120141979
Davis Corner120231988
Tipton120152000
Lafayette120132013

Scarlet Tanager Population Trend in Other States

alabamaarkansasconnecticutdelawaregeorgiaillinoisindianakansaskentuckymainemarylandmassachusettsmichiganminnesotamississippimissourinebraskanew-hampshirenew-jerseynew-yorknorth-carolinanorth-dakotaohiooklahomapennsylvaniarhode-islandsouth-carolinatennesseevermontvirginiawest-virginiawisconsin

Source: USGS North American Breeding Bird Survey, retrieved 2026-08-14.