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

Willow Flycatcher Population Trend in Massachusetts

All statesAerial insectivores

Willow Flycatcher in Massachusetts has surged: up 404% on the route-weighted index since 1970.

+404%Since 1970TrendPercent 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 →
25Routes 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 →
55YearsYears surveyedNumber of years with at least one standard-protocol run in this geography. A longer record makes the trend more reliable.Full methodology →

Notable Willow Flycatcher 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 →

Willow Flycatcher has surged in Massachusetts: up 404% on the route-weighted index since 1970.

Willow Flycatcher Population Forecast in Massachusetts

If the recent trend holds, Willow Flycatcher in Massachusetts is projected to rise about 21% by 2029 — from 0.53 in 2024 to a central estimate of 0.65 (95% range 0.33–0.96). A 5-year backtest shows a typical error of ±32.5%, with 100% of held-out values landing inside the 95% band.

+21%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 →
0.65Projected 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 →
0.33–0.9695% 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 →
±32.5%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, Willow Flycatcher in Massachusetts is projected to rise about 21% by 2029 — from 0.53 in 2024 to a central estimate of 0.65 (95% range 0.33–0.96). A 5-year backtest shows a typical error of ±32.5%, with 100% of held-out values landing inside the 95% band.19682029
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 →
20250.620.300.93
20260.630.310.94
20270.630.320.95
20280.640.330.95
20290.650.330.96

Willow Flycatcher Survey Routes in Massachusetts

Routes recording Willow Flycatcher 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 →
N. Andover720241995
Warren420091969
Chesterfield320211977
E Dennis220141986
Belchertown220191968
Ware River120161993
Prattville120192000
Cape Cod Ns119991999
Newburyport120221968
Maynard120211988
Littleton120191972
N Oxford119961996
E Pepperell119941981
S Barre120231975
N Orange120191990
Cummington119871984
Cheshire119941973
Pittsfield120091989
Sheffield120221974
Monterey120232023
Gay Head120242001
Holden120231983
Warren 2120222010
Cummington 2120222016
Hancock120152011

Willow Flycatcher Population Trend in Other States

alaskaarizonaarkansascaliforniacoloradoconnecticutdelawaregeorgiaidahoillinoisindianaiowakansaskentuckymainemarylandmichiganminnesotamissourimontananebraskanevadanew-hampshirenew-jerseynew-mexiconew-yorknorth-carolinanorth-dakotaohiooklahomaoregonpennsylvaniarhode-islandsouth-dakotatennesseetexasutahvermontvirginiawashingtonwest-virginiawisconsinwyoming

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