BirdAnalyst
Species · BBS 2025 Release · 1966–2024

Chestnut-sided Warbler

ParulidaeForest birdsSetophaga pensylvanica

Chestnut-sided Warbler has edged down: down 11% on the route-weighted index since 1968.

-11%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 →
847RoutesSurvey routesHow many standard-protocol BBS routes contributed counts. More routes means a steadier, better-sampled index; very thin coverage is suppressed.Full methodology →
58Years SurveyedYears surveyedNumber of years with at least one standard-protocol run in this geography. A longer record makes the trend more reliable.Full methodology →

About the Chestnut-sided Warbler

The Chestnut-sided Warbler (Setophaga pensylvanica) is a North American member of the Wood-Warblers (Parulidae). In this analysis it is grouped with the forest birds.

Size
4.5–5.5 in long (11–14 cm) — a small, active songbird (typical for the family)
Habitat
Woodlands and forest edges, including wooded suburbs and parks.
Diet
Insects and spiders gleaned from foliage and bark, with seeds and berries in season.
Range
Recorded on 847 Breeding Bird Survey routes across 30 states, most concentrated in the Appalachian Mountains.
Family
Parulidae · Forest birds

Notable Chestnut-sided Warbler TrendsNotable signalsLong-arc shifts the engine flags automatically — sustained declines or increases large enough to stand out from year-to-year noise.Full methodology →

No notable trend signals for Chestnut-sided Warbler. See the full index history below.

Chestnut-sided Warbler Population Forecast

If the recent trend holds, Chestnut-sided Warbler is projected to fall about 23% by 2029 — from 1.3 in 2024 to a central estimate of 1.0 (95% range 0.76–1.3). A 5-year backtest shows a typical error of ±20.9%, with 40% of held-out values landing inside the 95% band.

-23%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 →
1.0Projected 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 →
0.76–1.395% 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 →
±20.9%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 is projected to fall about 23% by 2029 — from 1.3 in 2024 to a central estimate of 1.0 (95% range 0.76–1.3). A 5-year backtest shows a typical error of ±20.9%, with 40% of held-out values landing inside the 95% band.19662029
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 →
20251.10.791.4
20261.10.781.3
20271.10.771.3
20281.00.761.3
20291.00.761.3

Where the Chestnut-sided Warbler Is Detected

BBS routes recording Chestnut-sided Warbler, sized by most recent count.

Chestnut-sided Warbler Population Trend by State

Chestnut-sided Warbler population trend by state.
TrendPercent 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 →Baseline yearThe first year of the smoothed window the trend is measured from. An earlier baseline means a longer record stands behind the number.Full methodology →Survey routesHow many standard-protocol BBS routes contributed counts. More routes means a steadier, better-sampled index; very thin coverage is suppressed.Full methodology →
Alabamainsufficient datan/a2
Arkansas+23%20076
Coloradoinsufficient datan/a1
Connecticut-62%196820
Georgiainsufficient datan/a2
Illinoisinsufficient datan/a6
Indiana-21%198112
Iowainsufficient datan/a2
Kansasinsufficient datan/a1
Kentuckyinsufficient datan/a3
Maine+9%196877
Maryland+114%196813
Massachusetts+50%196828
Michigan+100%196892
Minnesota+57%196956
Nevadainsufficient datan/a1
New Hampshire+4%196826
New Jersey+47%197020
New York+76%1968123
North Carolina-11%197024
North Dakotainsufficient datan/a1
Ohio+78%197620
Pennsylvania+107%1968112
Rhode Island-63%19686
Tennessee+19%196810
Vermont+42%196826
Virginia+402%196927
West Virginia+365%196841
Wisconsin+114%196887
Wyominginsufficient datan/a2

Chestnut-sided Warbler Population Trend by Region

Bird Conservation Regions are the ecological unit for trends.

Chestnut-sided Warbler population trend by Bird Conservation Region.
TrendPercent 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 →Baseline yearThe first year of the smoothed window the trend is measured from. An earlier baseline means a longer record stands behind the number.Full methodology →Survey routesHow many standard-protocol BBS routes contributed counts. More routes means a steadier, better-sampled index; very thin coverage is suppressed.Full methodology →
Prairie Potholes-53%19799
Boreal Hardwood Transition+74%1968124
Lower Great Lakes / St. Lawrence Plain+88%196878
Atlantic Northern Forest+15%1968155
Eastern Tallgrass Prairie-16%198314
Prairie Hardwood Transition+87%1968109
Central Hardwoods-37%199910
Appalachian Mountains+117%1968261
Piedmont-75%197119
New England / Mid-Atlantic Coast-41%196862

Chestnut-sided Warbler Conservation Status

Our route-weighted index shows it down about 11% since 1968.

Source: USGS North American Breeding Bird Survey, retrieved 2026-05-22. Trend is a route-weighted relative-abundance index, not an absolute population.