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Species · Massachusetts · BBS 2025 Release · 1966–2024

Blue-gray Gnatcatcher Population Trend in Massachusetts

All statesForest birds

Blue-gray Gnatcatcher in Massachusetts has surged: up 14× on the route-weighted index since 1978.

14×Since 1978TrendPercent 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 →
24Routes 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 →
38YearsYears surveyedNumber of years with at least one standard-protocol run in this geography. A longer record makes the trend more reliable.Full methodology →

Notable Blue-gray Gnatcatcher Trends in MassachusettsNotable 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 increasecomputed 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 →

Blue-gray Gnatcatcher has surged in Massachusetts: up 14× on the route-weighted index since 1978.

Blue-gray Gnatcatcher Population Forecast in Massachusetts

If the recent trend holds, Blue-gray Gnatcatcher in Massachusetts is projected to fall about 37% by 2029 — from 1.5 in 2024 to a central estimate of 0.92 (95% range 0.36–1.5). A 5-year backtest shows a typical error of ±43.5%, with 40% of held-out values landing inside the 95% band.

-37%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 →
0.92Projected 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 →
0.36–1.595% 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 →
±43.5%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, Blue-gray Gnatcatcher in Massachusetts is projected to fall about 37% by 2029 — from 1.5 in 2024 to a central estimate of 0.92 (95% range 0.36–1.5). A 5-year backtest shows a typical error of ±43.5%, with 40% of held-out values landing inside the 95% band.19752029
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 →
20250.850.291.4
20260.860.301.4
20270.890.321.4
20280.900.341.5
20290.920.361.5

Blue-gray Gnatcatcher Survey Routes in Massachusetts

Routes recording Blue-gray Gnatcatcher in Massachusetts.
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 →
Belchertown920241975
S Barre520242013
Marion420242013
Warren420091975
Brockton220192016
Maynard220221998
Chesterfield220011988
Sheffield220041979
Chilmark119831983
Wellfleet119941994
Prattville120181999
Newburyport120171997
Littleton120012000
N Oxford120242005
Mansfield120232014
Ware River120211997
E Pepperell119841984
N Orange120142009
Pittsfield120032003
Gay Head120222022
Wellfleet 2120172017
Holden120241999
N. Andover120241995
Warren 2120242011

Blue-gray Gnatcatcher Population Trend in Other States

alabamaarizonaarkansascaliforniacoloradoconnecticutdelawarefloridageorgiaidahoillinoisindianaiowakansaskentuckylouisianamainemarylandmichiganminnesotamississippimissourinebraskanevadanew-hampshirenew-jerseynew-mexiconew-yorknorth-carolinaohiooklahomaoregonpennsylvaniarhode-islandsouth-carolinasouth-dakotatennesseetexasutahvermontvirginiawest-virginiawisconsinwyoming

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