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

Barn Swallow Population Trend in South Carolina

All statesAerial insectivores

Barn Swallow in South Carolina has surged: up 398% on the route-weighted index since 1968.

+398%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 →
49Routes 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 Barn 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 →

Barn Swallow has surged in South Carolina: up 398% on the route-weighted index since 1968.

Barn Swallow Population Forecast in South Carolina

If the recent trend holds, Barn Swallow in South Carolina is projected to rise about 29% by 2029 — from 7.5 in 2024 to a central estimate of 9.6 (95% range 6.5–13). A 5-year backtest shows a typical error of ±24%, with 40% of held-out values landing inside the 95% band.

+29%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 →
9.6Projected 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 →
6.5–1395% 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 →
±24%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, Barn Swallow in South Carolina is projected to rise about 29% by 2029 — from 7.5 in 2024 to a central estimate of 9.6 (95% range 6.5–13). A 5-year backtest shows a typical error of ±24%, with 40% 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 →
20259.26.112
20269.36.212
20279.46.313
20289.56.413
20299.66.513

Barn Swallow Survey Routes in South Carolina

Routes recording Barn 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 →
Pinewood4920191999
Joanna4520231999
Holly Hill4020241979
New Holland3820241967
Dillon3120211978
Bennettsville3020171998
Pendleton1819761966
Foreston1720211978
Hardeeville1420241972
Ridgeway1420212010
Coward1220241969
Walterboro1220171992
Little Mtn1219881968
Olar1220191998
Plum Branch920231977
Ward920212017
Campobello920242011
Nixville920171998
Prosperity820231992
Red Bluff820241996
Rome720241976
Nixonville719951987
New Ellenton720232010
Bishopville620241975
Landrum619921972

Barn 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.