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

Purple Martin Population Trend in Iowa

All statesAerial insectivores

Purple Martin in Iowa has declined: down 26% on the route-weighted index since 1969.

-26%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 →
35Routes 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 →
57YearsYears surveyedNumber of years with at least one standard-protocol run in this geography. A longer record makes the trend more reliable.Full methodology →

Notable Purple Martin 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 Purple Martin in Iowa. See the full index history below.

Purple Martin Population Forecast in Iowa

If the recent trend holds, Purple Martin in Iowa is projected to fall about 70% by 2029 — from 3.9 in 2024 to a central estimate of 1.2 (95% range 0.00–2.8). A 5-year backtest shows a typical error of ±54.9%, with 60% of held-out values landing inside the 95% band.

-70%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 →
1.2Projected 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 →
0.00–2.895% 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 →
±54.9%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, Purple Martin in Iowa is projected to fall about 70% by 2029 — from 3.9 in 2024 to a central estimate of 1.2 (95% range 0.00–2.8). A 5-year backtest shows a typical error of ±54.9%, with 60% of held-out values landing inside the 95% band.19672029
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 →
20251.20.002.9
20261.20.002.9
20271.20.002.9
20281.20.002.8
20291.20.002.8

Purple Martin Survey Routes in Iowa

Routes recording Purple Martin 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 →
Exline4920241974
West Liberty2020241969
Scranton1719991967
Melrose1220241981
Alice1219971973
Bedford619881968
Davis Corner619881968
Festina519871971
Titonka519811975
Maquoketa419861967
Desmoines319741968
Panther320221967
Neola320111968
Prairieburg319861967
Mt Hamill220241967
Williamsburg219931967
Washington220241967
Wales219721968
Hudson219701967
Kanawha219861974
Clare220091977
Pierson220001968
Washta220001968
Garner219901975
Gaza219831969

Purple Martin Population Trend in Other States

alabamaarizonaarkansascaliforniacoloradoconnecticutdelawarefloridageorgiaillinoisindianakansaskentuckylouisianamainemarylandmassachusettsmichiganminnesotamississippimissourimontananebraskanew-hampshirenew-jerseynew-mexiconew-yorknorth-carolinanorth-dakotaohiooklahomaoregonpennsylvaniarhode-islandsouth-carolinasouth-dakotatennesseetexasutahvermontvirginiawashingtonwest-virginiawisconsinwyoming

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