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

Purple Martin Population Trend in Vermont

All statesAerial insectivores

Purple Martin in Vermont has fallen sharply: down 71% on the route-weighted index since 1969.

-71%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 →
8Routes 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 →
22YearsYears 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 VermontNotable 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 →

Purple Martin has fallen sharply in Vermont: down 71% on the route-weighted index since 1969.

Purple Martin Population Forecast in Vermont

If the recent trend holds, Purple Martin in Vermont is projected to fall about 100% by 2003 — from 0.60 in 1998 to a central estimate of 0.00 (95% range 0.00–0.95). A 5-year backtest shows a typical error of ±819.5%, with 100% of held-out values landing inside the 95% band.

-100%Change by 2003TrendPercent 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 →
0.00Projected 2003 indexProjected indexThe central forecast of the abundance index if the recent trend continues. A projection of the current trajectory, not a prediction.Full methodology →
0.00–0.9595% 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 →
±819.5%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, Purple Martin in Vermont is projected to fall about 100% by 2003 — from 0.60 in 1998 to a central estimate of 0.00 (95% range 0.00–0.95). A 5-year backtest shows a typical error of ±819.5%, with 100% of held-out values landing inside the 95% band.19672003
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 →
19990.090.001.0
20000.050.001.0
20010.010.000.97
20020.000.000.95
20030.000.000.95

Purple Martin Survey Routes in Vermont

Routes recording Purple Martin in Vermont.
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 →
Grand Isle1219981967
Greensboro319681968
East Calais219761972
Hinesburg219891978
S Wallingfrd119831983
East Haven119751975
Hardwick119781978
Waterville119751970

Purple Martin Population Trend in Other States

alabamaarizonaarkansascaliforniacoloradoconnecticutdelawarefloridageorgiaillinoisindianaiowakansaskentuckylouisianamainemarylandmassachusettsmichiganminnesotamississippimissourimontananebraskanew-hampshirenew-jerseynew-mexiconew-yorknorth-carolinanorth-dakotaohiooklahomaoregonpennsylvaniarhode-islandsouth-carolinasouth-dakotatennesseetexasutahvirginiawashingtonwest-virginiawisconsinwyoming

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