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Species · Maryland · BBS 2025 Release · 1966–2024

Northern Rough-winged Swallow Population Trend in Maryland

All statesAerial insectivores

Northern Rough-winged Swallow in Maryland has surged: up 88% on the route-weighted index since 1968.

+88%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 →
67Routes 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 Northern Rough-winged Swallow 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 →

Northern Rough-winged Swallow has surged in Maryland: up 87% on the route-weighted index since 1968.

Northern Rough-winged Swallow Population Forecast in Maryland

If the recent trend holds, Northern Rough-winged Swallow in Maryland is projected to fall about 15% by 2029 — from 0.74 in 2024 to a central estimate of 0.63 (95% range 0.18–1.1). A 5-year backtest shows a typical error of ±30.1%, with 100% of held-out values landing inside the 95% band.

-15%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 →
0.63Projected 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 →
0.18–1.195% 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 →
±30.1%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, Northern Rough-winged Swallow in Maryland is projected to fall about 15% by 2029 — from 0.74 in 2024 to a central estimate of 0.63 (95% range 0.18–1.1). A 5-year backtest shows a typical error of ±30.1%, 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 →
20250.620.171.1
20260.620.181.1
20270.620.181.1
20280.630.181.1
20290.630.181.1

Northern Rough-winged Swallow Survey Routes in Maryland

Routes recording Northern Rough-winged Swallow 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 →
Bachman Mill920241967
Williamsport820241966
Madonna820222011
Elkton620231969
Olney520241971
Floyd420191967
Beltsville420081966
Finzel420242002
Forest Grove420232011
Bald Friar319961996
Eklo319981971
Largo319661966
Indiantown320101979
Fair Hill319961993
Potomac Park220241971
Pleasant Val220081966
Randallstown220041974
Van Bibber220061967
Pt Republic219661966
La Plata220091969
Melitota220131966
Piney Neck220221966
Harmony220171967
Golden Hill220082001
Fruitland219981967

Northern Rough-winged Swallow Population Trend in Other States

alabamaalaskaarizonaarkansascaliforniacoloradoconnecticutdelawarefloridageorgiaidahoillinoisindianaiowakansaskentuckylouisianamainemassachusettsmichiganminnesotamississippimissourimontananebraskanevadanew-hampshirenew-jerseynew-mexiconew-yorknorth-carolinanorth-dakotaohiooklahomaoregonpennsylvaniarhode-islandsouth-carolinasouth-dakotatennesseetexasutahvermontvirginiawashingtonwest-virginiawisconsinwyoming

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