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

Carolina Wren Population Trend in Iowa

All statesForest birds

Carolina Wren in Iowa has surged: up 149% on the route-weighted index since 1971.

+149%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 →
10Routes 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 →
23YearsYears surveyedNumber of years with at least one standard-protocol run in this geography. A longer record makes the trend more reliable.Full methodology →

Notable Carolina Wren 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 Carolina Wren in Iowa. See the full index history below.

Carolina Wren Population Forecast in Iowa

If the recent trend holds, Carolina Wren in Iowa is projected to rise about 49% by 2030 — from 0.07 in 2025 to a central estimate of 0.10 (95% range 0.00–0.20). A 5-year backtest shows a typical error of ±45.3%, with 60% of held-out values landing inside the 95% band.

+49%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 →
0.10Projected 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 →
0.00–0.2095% 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 →
±45.3%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, Carolina Wren in Iowa is projected to rise about 49% by 2030 — from 0.07 in 2025 to a central estimate of 0.10 (95% range 0.00–0.20). A 5-year backtest shows a typical error of ±45.3%, with 60% 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 →
20260.090.000.19
20270.090.000.19
20280.100.000.19
20290.100.000.20
20300.100.000.20

Carolina Wren Survey Routes in Iowa

Routes recording Carolina Wren 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 →
Alice419911991
College Spgs 2220182017
Red Rock220252018
Mt Hamill120191967
Exline119781976
West Liberty119751975
Cedar Valley119761976
Tipton120172017
Wales119911991
Maquoketa120181992

Carolina Wren Population Trend in Other States

alabamaarkansasconnecticutdelawarefloridageorgiaillinoisindianakansaskentuckylouisianamainemarylandmassachusettsmichiganminnesotamississippimissourinebraskanew-hampshirenew-jerseynew-yorknorth-carolinaohiooklahomapennsylvaniarhode-islandsouth-carolinatennesseetexasvermontvirginiawest-virginiawisconsin

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