BirdAnalyst
Species · South Carolina · BBS 2025 Release · 1966–2024

Northern Rough-winged Swallow Population Trend in South Carolina

All statesAerial insectivores

Northern Rough-winged Swallow in South Carolina has surged: up 239% on the route-weighted index since 1968.

+239%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 →
42Routes 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 South CarolinaNotable 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 South Carolina: up 239% on the route-weighted index since 1968.

Northern Rough-winged Swallow Population Forecast in South Carolina

If the recent trend holds, Northern Rough-winged Swallow in South Carolina is projected to fall about 30% by 2029 — from 1.9 in 2024 to a central estimate of 1.3 (95% range 0.00–3.9). A 5-year backtest shows a typical error of ±43.3%, with 80% of held-out values landing inside the 95% band.

-30%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 →
1.3Projected 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 →
0.00–3.995% 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 →
±43.3%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 South Carolina is projected to fall about 30% by 2029 — from 1.9 in 2024 to a central estimate of 1.3 (95% range 0.00–3.9). A 5-year backtest shows a typical error of ±43.3%, 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 →
20251.30.003.9
20261.30.003.9
20271.30.003.9
20281.30.003.9
20291.30.003.9

Northern Rough-winged Swallow Survey Routes in South Carolina

Routes recording Northern Rough-winged Swallow in South Carolina.
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 →
Barton Creek3020221968
Campobello2520242016
Whitmire1420242024
Joanna1320231999
Boykin Ml Pd819681968
Little Mtn819881980
Battlecreek820142000
Salem620232010
Bishopville419861974
Plum Branch420221977
Carvers Bay420122012
Rome320091973
Walterboro320171993
Salem Xrd320191984
Pendleton319761966
Holly Hill220191975
Coward220051966
New Holland220101973
Boiling Spgs219711970
Landrum219921986
New Ellenton220182018
Blacksburg220112000
Bennettsville220081999
Olar220071998
Pinewood219981998

Northern Rough-winged Swallow Population Trend in Other States

alabamaalaskaarizonaarkansascaliforniacoloradoconnecticutdelawarefloridageorgiaidahoillinoisindianaiowakansaskentuckylouisianamainemarylandmassachusettsmichiganminnesotamississippimissourimontananebraskanevadanew-hampshirenew-jerseynew-mexiconew-yorknorth-carolinanorth-dakotaohiooklahomaoregonpennsylvaniarhode-islandsouth-dakotatennesseetexasutahvermontvirginiawashingtonwest-virginiawisconsinwyoming

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