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

Bobolink Population Trend in Iowa

All statesGrassland birds

Bobolink in Iowa has collapsed: down 76% on the route-weighted index since 1969.

-76%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 →
38Routes 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 Bobolink 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 →

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 →

Bobolink has collapsed in Iowa: down 76% on the route-weighted index since 1969.

Bobolink Population Forecast in Iowa

If the recent trend holds, Bobolink in Iowa is projected to fall about 35% by 2029 — from 2.3 in 2024 to a central estimate of 1.5 (95% range 0.00–5.5). A 5-year backtest shows a typical error of ±19.5%, with 100% of held-out values landing inside the 95% band.

-35%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 →
1.5Projected 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 →
0.00–5.595% 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 →
±19.5%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, Bobolink in Iowa is projected to fall about 35% by 2029 — from 2.3 in 2024 to a central estimate of 1.5 (95% range 0.00–5.5). A 5-year backtest shows a typical error of ±19.5%, with 100% 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 →
20252.00.006.0
20261.90.005.9
20271.80.005.7
20281.60.005.6
20291.50.005.5

Bobolink Survey Routes in Iowa

Routes recording Bobolink 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 →
Bedford1720181968
Burchinal1420241995
Washta1220141967
Davis Corner720241968
Hudson620221967
Festina620221968
Brooklyn520211967
Wales520181971
Kanawha520241967
Bryant420241967
Maquoketa420241967
Alice419941967
Scranton420241967
Pierson420141968
Sioux City419821970
Mt Hamill320241967
Exline320241974
Prairieburg320111967
Gaza320231969
Melrose220241974
College Spgs219921979
Cedar Valley219971967
Panther220241967
Dinsdale219961968
Clare220191967

Bobolink Population Trend in Other States

californiacoloradoconnecticutidahoillinoisindianakansaskentuckymainemarylandmassachusettsmichiganminnesotamissourimontananebraskanevadanew-hampshirenew-jerseynew-mexiconew-yorknorth-carolinanorth-dakotaohiooregonpennsylvaniarhode-islandsouth-dakotautahvermontvirginiawashingtonwest-virginiawisconsinwyoming

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