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Species · BCR 4 · BBS 2025 Release · 1966–2024

Violet-green Swallow In BCR 4

All regionsBCR 4Aerial insectivores

Violet-green Swallow in BCR 4 has risen sharply: up 70% on the route-weighted index since 1978.

+70%Since 1978TrendPercent 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 →
53Routes In RegionSurvey routesHow many standard-protocol BBS routes contributed counts. More routes means a steadier, better-sampled index; very thin coverage is suppressed.Full methodology →
45YearsYears surveyedNumber of years with at least one standard-protocol run in this geography. A longer record makes the trend more reliable.Full methodology →

Notable SignalsNotable 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 →

Violet-green Swallow has risen sharply in BCR 4: up 70% on the route-weighted index since 1978.

Violet-green Swallow In BCR 4 Population Forecast

If the recent trend holds, Violet-green Swallow in BCR 4 is projected to fall about 50% by 2029 — from 1.8 in 2024 to a central estimate of 0.91 (95% range 0.00–3.4). A 5-year backtest shows a typical error of ±36.5%, with 100% of held-out values landing inside the 95% band.

-50%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 →
0.91Projected 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 →
0.00–3.495% 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 →
±36.5%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, Violet-green Swallow in BCR 4 is projected to fall about 50% by 2029 — from 1.8 in 2024 to a central estimate of 0.91 (95% range 0.00–3.4). A 5-year backtest shows a typical error of ±36.5%, with 100% of held-out values landing inside the 95% band.19682029
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 →
20251.10.003.6
20261.00.003.5
20270.990.003.5
20280.950.003.5
20290.910.003.4

Routes In BCR 4

Routes recording Violet-green Swallow in BCR 4.
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 →
MatanuskaALASKA141983
EagleALASKA132024
WillowALASKA112024
Kenny LakeALASKA112024
ChistochinaALASKA102022
KachemakALASKA102024
CircleALASKA82011
Anchor RiverALASKA82024
Kanuti CanynALASKA82024
HomerALASKA51982
McgrathALASKA52022
TatalinaALASKA52019
ChickenALASKA42024
DeltaALASKA42007
Paxson LakeALASKA41995
Goose BayALASKA31982
Hatcher PassALASKA32017
Chena Hot Spring 2ALASKA32013
Lake LouiseALASKA32005
PetersvilleALASKA32012
ColdfootALASKA32022
Donelly DomeALASKA32011
CottonwoodALASKA31989
Manley Ht SpALASKA32022
Mccarthy Rd2ALASKA32021

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