BirdAnalyst
Species · BCR 14 · BBS 2025 Release · 1966–2024

Northern Harrier In Atlantic Northern Forest

All regionsAtlantic Northern ForestGeneralists

Northern Harrier in Atlantic Northern Forest has fallen sharply: down 52% on the route-weighted index since 1974.

-52%Since 1974TrendPercent 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 →
44YearsYears 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 →

Northern Harrier has fallen sharply in Atlantic Northern Forest: down 52% on the route-weighted index since 1974.

Forecast

If the recent trend holds, Northern Harrier in Atlantic Northern Forest is projected to stay roughly flat through 2027, near 0.03 (95% range 0.00–0.07). A 5-year backtest shows a typical error of ±70.7%, with 100% of held-out values landing inside the 95% band.

n/aChange by 2027TrendPercent 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 →
0.03Projected 2027 indexProjected indexThe central forecast of the abundance index if the recent trend continues. A projection of the current trajectory, not a prediction.Full methodology →
0.00–0.0795% 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 →
±70.7%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 Harrier in Atlantic Northern Forest is projected to stay roughly flat through 2027, near 0.03 (95% range 0.00–0.07). A 5-year backtest shows a typical error of ±70.7%, with 100% of held-out values landing inside the 95% band.19662027
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 →
20230.030.000.07
20240.030.000.07
20250.030.000.07
20260.030.000.07
20270.030.000.07

Routes In Atlantic Northern Forest

Routes recording Northern Harrier in Atlantic Northern Forest.
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 →
HancockMAINE21987
Ft FairfieldMAINE22004
Number FourNEW-YORK22008
W RutlandVERMONT22003
WestbrookMAINE11986
South ArmMAINE11995
Otisfield GrMAINE11999
ManchesterMAINE11982
HarmonyMAINE12022
BrooksMAINE12006
EastbrookMAINE12017
CooperMAINE11978
DebloisMAINE12005
Moose RiverMAINE12006
WytopitlockMAINE11983
Forest StaMAINE11983
LudlowMAINE11981
WashburnMAINE11987
Horse MtnMAINE11995
AshlandMAINE12004
BoundaryMAINE12015
St DavidMAINE12005
JeffersonMAINE12008
Church HillMAINE12002
Heron LakeMAINE11989

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