BirdAnalyst
Species · New Hampshire · BBS 2025 Release · 1966–2024

Purple Martin Population Trend in New Hampshire

All statesAerial insectivores

Purple Martin in New Hampshire has fallen sharply: down 57% on the route-weighted index since 1968.

-57%Since 1968TrendPercent 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 →
7Routes 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 New HampshireNotable 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 New Hampshire: down 57% on the route-weighted index since 1968.

Purple Martin Population Forecast in New Hampshire

If the recent trend holds, Purple Martin in New Hampshire is projected to rise about 29% by 2005 — from 0.09 in 2000 to a central estimate of 0.11 (95% range 0.00–0.35). A 5-year backtest shows a typical error of ±130.5%, with 100% of held-out values landing inside the 95% band.

+29%Change by 2005TrendPercent 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 →
0.11Projected 2005 indexProjected indexThe central forecast of the abundance index if the recent trend continues. A projection of the current trajectory, not a prediction.Full methodology →
0.00–0.3595% 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 →
±130.5%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 New Hampshire is projected to rise about 29% by 2005 — from 0.09 in 2000 to a central estimate of 0.11 (95% range 0.00–0.35). A 5-year backtest shows a typical error of ±130.5%, with 100% of held-out values landing inside the 95% band.19662005
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 →
20010.140.000.37
20020.130.000.37
20030.120.000.36
20040.120.000.35
20050.110.000.35

Purple Martin Survey Routes in New Hampshire

Routes recording Purple Martin in New Hampshire.
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 →
Hopkinton719851966
Gilmantn I W619901989
Crawford Not419721967
Lempster220002000
Dover119791967
Strafford119961971
Jefferson Hl119721972

Purple Martin Population Trend in Other States

alabamaarizonaarkansascaliforniacoloradoconnecticutdelawarefloridageorgiaillinoisindianaiowakansaskentuckylouisianamainemarylandmassachusettsmichiganminnesotamississippimissourimontananebraskanew-jerseynew-mexiconew-yorknorth-carolinanorth-dakotaohiooklahomaoregonpennsylvaniarhode-islandsouth-carolinasouth-dakotatennesseetexasutahvermontvirginiawashingtonwest-virginiawisconsinwyoming

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