BirdAnalyst
Species · BBS 2025 Release · 1966–2024

Kentucky Warbler

ParulidaeForest birdsGeothlypis formosa

Kentucky Warbler has declined: down 38% on the route-weighted index since 1968.

-38%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 →
1,217RoutesSurvey 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 Kentucky Warbler

The Kentucky Warbler (Geothlypis formosa) 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 1,217 Breeding Bird Survey routes across 26 states, most concentrated in the Appalachian Mountains.
Family
Parulidae · Forest birds

Notable Kentucky 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 Kentucky Warbler. See the full index history below.

Kentucky Warbler Population Forecast

If the recent trend holds, Kentucky Warbler is projected to stay roughly flat through 2029, near 0.37 (95% range 0.24–0.50). A 5-year backtest shows a typical error of ±9.7%, with 100% of held-out values landing inside the 95% band.

-9%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 →
0.37Projected 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 →
0.24–0.5095% 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 →
±9.7%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, Kentucky Warbler is projected to stay roughly flat through 2029, near 0.37 (95% range 0.24–0.50). A 5-year backtest shows a typical error of ±9.7%, with 100% 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 →
20250.380.250.51
20260.380.250.50
20270.380.250.50
20280.370.240.50
20290.370.240.50

Where the Kentucky Warbler Is Detected

BBS routes recording Kentucky Warbler, sized by most recent count.

Kentucky Warbler Population Trend by State

Kentucky 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 →
Alabama+24%1968101
Arkansas-2%196952
Delaware-80%196815
Florida-53%197324
Georgia+7%196884
Illinois+224%197047
Indiana+100%196838
Iowainsufficient datan/a2
Kansas+311%197713
Kentucky+22%196862
Louisiana+9%196968
Maryland-74%196874
Mississippi+194%196867
Missouri+580%196976
New Jersey+14%197019
New Yorkinsufficient datan/a2
North Carolina-63%196872
Ohio+96%196846
Oklahoma+125%196927
Pennsylvania-90%196871
South Carolina+62%196836
Tennessee+47%196852
Texas-55%196935
Virginia-90%196873
West Virginia-80%196860
Wisconsininsufficient datan/a1

Kentucky Warbler Population Trend by Region

Bird Conservation Regions are the ecological unit for trends.

Kentucky 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 →
Lower Great Lakes / St. Lawrence Plain-26%19718
Oaks and Prairies-0%197013
Eastern Tallgrass Prairie+386%1968109
Central Hardwoods+63%1968159
West Gulf Coastal Plain / Ouachitas-34%1969109
Mississippi Alluvial Valley-8%196950
Southeastern Coastal Plain+90%1968260
Appalachian Mountains-63%1968291
Piedmont-34%1968132
New England / Mid-Atlantic Coast-80%196878

Kentucky Warbler Conservation Status

Our route-weighted index shows it down about 38% 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.