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Species · Connecticut · BBS 2026 Release · 1966–2025

Northern Rough-winged Swallow Population Trend in Connecticut

All statesAerial insectivores

Northern Rough-winged Swallow in Connecticut has surged: up 225% on the route-weighted index since 1969.

+225%Since 1969TrendPercent 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 →
18Routes 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 →
54YearsYears 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 ConnecticutNotable 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 Connecticut: up 225% on the route-weighted index since 1969.

Northern Rough-winged Swallow Population Forecast in Connecticut

If the recent trend holds, Northern Rough-winged Swallow in Connecticut is projected to rise about 28% by 2030 — from 1.4 in 2025 to a central estimate of 1.8 (95% range 0.10–3.4). A 5-year backtest shows a typical error of ±73.1%, with 100% of held-out values landing inside the 95% band.

+28%Change by 2030TrendPercent 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 →
1.8Projected 2030 indexProjected indexThe central forecast of the abundance index if the recent trend continues. A projection of the current trajectory, not a prediction.Full methodology →
0.10–3.495% 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 →
±73.1%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 Connecticut is projected to rise about 28% by 2030 — from 1.4 in 2025 to a central estimate of 1.8 (95% range 0.10–3.4). A 5-year backtest shows a typical error of ±73.1%, with 100% of held-out values landing inside the 95% band.19672030
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 →
20261.70.023.3
20271.70.043.4
20281.70.063.4
20291.70.083.4
20301.80.103.4

Northern Rough-winged Swallow Survey Routes in Connecticut

Routes recording Northern Rough-winged Swallow in Connecticut.
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 →
Uncasville620251982
Buckingham520221981
Danbury520171976
Sherman420191974
Mystic320131977
New Hartford320061994
Westbrook320251974
Southington220171995
Warren 2220222022
E Hartland119921968
Willimantic120141967
No Woodbury120101980
Greenwich120081974
Warren120091977
Long Hill120181977
Mid Haddam120251975
New Hartford119871973
Granby120251990

Northern Rough-winged Swallow Population Trend in Other States

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

Source: USGS North American Breeding Bird Survey, retrieved 2026-08-14.