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Species · Connecticut · BBS 2026 Release · 1966–2025

Chestnut-sided Warbler Population Trend in Connecticut

All statesForest birds

Chestnut-sided Warbler in Connecticut has fallen sharply: down 62% on the route-weighted index since 1968.

-62%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 →
20Routes 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 →
59YearsYears surveyedNumber of years with at least one standard-protocol run in this geography. A longer record makes the trend more reliable.Full methodology →

Notable Chestnut-sided Warbler Trends in ConnecticutNotable 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 →

Chestnut-sided Warbler has fallen sharply in Connecticut: down 62% on the route-weighted index since 1968.

Chestnut-sided Warbler Population Forecast in Connecticut

If the recent trend holds, Chestnut-sided Warbler in Connecticut is projected to rise about 36% by 2030 — from 2.3 in 2025 to a central estimate of 3.1 (95% range 0.00–6.7). A 5-year backtest shows a typical error of ±57.4%, with 100% of held-out values landing inside the 95% band.

+36%Change by 2030TrendPercent 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 →
3.1Projected 2030 indexProjected indexThe central forecast of the abundance index if the recent trend continues. A projection of the current trajectory, not a prediction.Full methodology →
0.00–6.795% 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 →
±57.4%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, Chestnut-sided Warbler in Connecticut is projected to rise about 36% by 2030 — from 2.3 in 2025 to a central estimate of 3.1 (95% range 0.00–6.7). A 5-year backtest shows a typical error of ±57.4%, with 100% of held-out values landing inside the 95% band.19662030
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 →
20263.20.006.9
20273.20.006.9
20283.10.006.8
20293.10.006.8
20303.10.006.7

Chestnut-sided Warbler Survey Routes in Connecticut

Routes recording Chestnut-sided Warbler in Connecticut.
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 →
Warren2920111972
Warren 2820252012
New Hartford519871972
E Hartland419921966
Woodstock420071968
No Woodbury420251967
Granby420251988
Sherman220191972
Long Hill220171974
Mystic120011973
Buckingham120211966
Uncasville120211973
Westbrook119991978
Willimantic120181967
Greenwich119971967
Danbury120191968
Mid Haddam120221973
Southington120251973
New Hartford120241994
Woodstock 2120252017

Chestnut-sided Warbler Population Trend in Other States

alabamaarkansascoloradogeorgiaillinoisindianaiowakansaskentuckymainemarylandmassachusettsmichiganminnesotanevadanew-hampshirenew-jerseynew-yorknorth-carolinanorth-dakotaohiopennsylvaniarhode-islandtennesseevermontvirginiawest-virginiawisconsinwyoming

Source: USGS North American Breeding Bird Survey, retrieved 2026-08-14.