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Species · Maryland · BBS 2025 Release · 1966–2024

Cerulean Warbler Population Trend in Maryland

All statesForest birds

Cerulean Warbler in Maryland has surged: up 117% on the route-weighted index since 1968.

+117%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 →
27Routes 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 →
58YearsYears surveyedNumber of years with at least one standard-protocol run in this geography. A longer record makes the trend more reliable.Full methodology →

Notable Cerulean Warbler Trends in MarylandNotable 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 →

Cerulean Warbler has surged in Maryland: up 117% on the route-weighted index since 1968.

Cerulean Warbler Population Forecast in Maryland

If the recent trend holds, Cerulean Warbler in Maryland is projected to fall about 33% by 2029 — from 0.31 in 2024 to a central estimate of 0.21 (95% range 0.08–0.33). A 5-year backtest shows a typical error of ±23.5%, with 80% of held-out values landing inside the 95% band.

-33%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 →
0.21Projected 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 →
0.08–0.3395% 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 →
±23.5%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, Cerulean Warbler in Maryland is projected to fall about 33% by 2029 — from 0.31 in 2024 to a central estimate of 0.21 (95% range 0.08–0.33). A 5-year backtest shows a typical error of ±23.5%, with 80% 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 →
20250.200.070.33
20260.200.070.33
20270.200.080.33
20280.200.080.33
20290.210.080.33

Cerulean Warbler Survey Routes in Maryland

Routes recording Cerulean Warbler in Maryland.
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 →
Oldtown620241970
Wolfsville220241966
Pomfret219661966
Theodore220131968
Green Ridge220241995
Piney Grove220241995
Floyd120121967
Mt Nebo119851975
Vindex119921968
Potomac Park120191972
Bald Friar119961996
Smithsburg120141972
Emmitsburg119841982
Fair Hill119951995
Olney119981983
Bachman Mill119841984
Upper Xrds119721972
Van Bibber120111966
Berlin119881988
Largo119731973
Earlton120242014
Jennings120181998
Steyer120102001
Finzel120171995
Accident120061994

Cerulean Warbler Population Trend in Other States

alabamaarkansasconnecticutgeorgiaillinoisindianakentuckylouisianamassachusettsmichiganminnesotamississippimissourinew-hampshirenew-jerseynew-yorknorth-carolinaohiooklahomapennsylvaniatennesseevermontvirginiawest-virginiawisconsin

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