BirdAnalyst
Species · Vermont · BBS 2025 Release · 1966–2024

Common Loon Population Trend in Vermont

All statesWetland birds

Common Loon in Vermont has surged: up 316% on the route-weighted index since 1978.

+316%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 →
10Routes 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 →
30YearsYears surveyedNumber of years with at least one standard-protocol run in this geography. A longer record makes the trend more reliable.Full methodology →

Notable Common Loon Trends in VermontNotable 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 →

Common Loon has surged in Vermont: up 316% on the route-weighted index since 1978.

Common Loon Population Forecast in Vermont

If the recent trend holds, Common Loon in Vermont is projected to fall about 33% by 2029 — from 0.28 in 2024 to a central estimate of 0.18 (95% range 0.07–0.30). A 5-year backtest shows a typical error of ±38.8%, with 60% of held-out values landing inside the 95% band.

-33%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 →
0.18Projected 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 →
0.07–0.3095% 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 →
±38.8%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, Common Loon in Vermont is projected to fall about 33% by 2029 — from 0.28 in 2024 to a central estimate of 0.18 (95% range 0.07–0.30). A 5-year backtest shows a typical error of ±38.8%, with 60% of held-out values landing inside the 95% band.19672029
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 →
20250.170.060.29
20260.180.060.29
20270.180.070.29
20280.180.070.30
20290.180.070.30

Common Loon Survey Routes in Vermont

Routes recording Common Loon in Vermont.
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 →
St Johnsbury220231990
Hardwick220241998
Stratton120102006
Post Mills120241978
Middlesex120232019
East Calais120222018
Greensboro120241967
Fletcher120232023
Newbury 2120222022
Grand Isle120241969

Common Loon Population Trend in Other States

alaskaidahomainemassachusettsmichiganminnesotamontananew-hampshirenew-yorknorth-dakotaoregonwashingtonwisconsinwyoming

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