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

Cliff Swallow In BCR 4

All regionsBCR 4Aerial insectivores

Cliff Swallow in BCR 4 has collapsed: down 75% on the route-weighted index since 1978.

-75%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 →
42Routes 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 →
43YearsYears 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 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 →

Cliff Swallow has collapsed in BCR 4: down 75% on the route-weighted index since 1978.

Forecast

If the recent trend holds, Cliff Swallow in BCR 4 is projected to fall about 100% by 2029 — from 1.1 in 2024 to a central estimate of 0.00 (95% range 0.00–8.3). A 5-year backtest shows a typical error of ±53.3%, with 100% of held-out values landing inside the 95% band.

-100%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 →
0.00Projected 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 →
0.00–8.395% 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 →
±53.3%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, Cliff Swallow in BCR 4 is projected to fall about 100% by 2029 — from 1.1 in 2024 to a central estimate of 0.00 (95% range 0.00–8.3). A 5-year backtest shows a typical error of ±53.3%, with 100% of held-out values landing inside the 95% band.19752029
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 →
20250.510.008.8
20260.300.008.6
20270.100.008.4
20280.000.008.3
20290.000.008.3

Routes In BCR 4

Routes recording Cliff 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 →
McgrathALASKA1812022
Tangle LakesALASKA851987
Paxson LakeALASKA551997
WasillaALASKA501983
Lake LouiseALASKA182011
Birch LakeALASKA152024
Goose BayALASKA151982
SourdoughALASKA132014
Hather CreekALASKA122003
CircleALASKA102019
CantwellALASKA102015
Chena Hot Spring 2ALASKA102004
Galena (Short)ALASKA102023
MaclarenALASKA92024
Mt. FairplayALASKA92024
Hatcher PassALASKA81993
PetersvilleALASKA82004
KalifonskyALASKA71982
NorthwayALASKA62023
Chena RiverALASKA61988
Anvik RiverALASKA62005
Anchor RiverALASKA52011
KachemakALASKA52006
Ft. RichrdsnALASKA51999
EagleALASKA42024

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