BirdAnalyst
Species · Delaware · BBS 2025 Release · 1966–2024

Northern Rough-winged Swallow Population Trend in Delaware

All statesAerial insectivores

Northern Rough-winged Swallow in Delaware has fallen sharply: down 60% on the route-weighted index since 1968.

-60%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 →
13Routes 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 →
50YearsYears 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 DelawareNotable 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 →

Northern Rough-winged Swallow has fallen sharply in Delaware: down 60% on the route-weighted index since 1968.

Northern Rough-winged Swallow Population Forecast in Delaware

If the recent trend holds, Northern Rough-winged Swallow in Delaware is projected to stay roughly flat through 2027, near 0.43 (95% range 0.00–2.1). A 5-year backtest shows a typical error of ±123.8%, with 100% of held-out values landing inside the 95% band.

+8%Change by 2027TrendPercent 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 →
0.43Projected 2027 indexProjected indexThe central forecast of the abundance index if the recent trend continues. A projection of the current trajectory, not a prediction.Full methodology →
0.00–2.195% 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 →
±123.8%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 Delaware is projected to stay roughly flat through 2027, near 0.43 (95% range 0.00–2.1). A 5-year backtest shows a typical error of ±123.8%, with 100% of held-out values landing inside the 95% band.19662027
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 →
20230.490.002.2
20240.480.002.2
20250.460.002.2
20260.450.002.1
20270.430.002.1

Northern Rough-winged Swallow Survey Routes in Delaware

Routes recording Northern Rough-winged Swallow in Delaware.
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 →
Lowes Xrds419781975
Mt Pleasant220061977
Wilmington220101987
Harrington220221977
Frederica220121970
Frankford219961968
Holleyville220031968
Milton220061967
Blackbird219941994
Georgetown219921992
Dover119851985
Bethany Bch119901966
Pepperbox119981998

Northern Rough-winged Swallow Population Trend in Other States

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

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