BirdAnalyst
Species · BCR 13 · BBS 2025 Release · 1966–2024

Northern Harrier In Lower Great Lakes / St. Lawrence Plain

All regionsLower Great Lakes / St. Lawrence PlainGeneralists

Northern Harrier in Lower Great Lakes / St. Lawrence Plain has risen sharply: up 74% on the route-weighted index since 1969.

+74%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 →
50Routes 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 →
51YearsYears 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 →

Northern Harrier has risen sharply in Lower Great Lakes / St. Lawrence Plain: up 74% on the route-weighted index since 1969.

Forecast

If the recent trend holds, Northern Harrier in Lower Great Lakes / St. Lawrence Plain is projected to fall about 11% by 2028 — from 0.09 in 2023 to a central estimate of 0.08 (95% range 0.00–0.20). A 5-year backtest shows a typical error of ±52.6%, with 100% of held-out values landing inside the 95% band.

-11%Change by 2028TrendPercent 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 →
0.08Projected 2028 indexProjected indexThe central forecast of the abundance index if the recent trend continues. A projection of the current trajectory, not a prediction.Full methodology →
0.00–0.2095% 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 →
±52.6%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 Lower Great Lakes / St. Lawrence Plain is projected to fall about 11% by 2028 — from 0.09 in 2023 to a central estimate of 0.08 (95% range 0.00–0.20). A 5-year backtest shows a typical error of ±52.6%, with 100% of held-out values landing inside the 95% band.19662028
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 →
20240.080.000.20
20250.080.000.20
20260.080.000.20
20270.080.000.20
20280.080.000.20

Routes In Lower Great Lakes / St. Lawrence Plain

Routes recording Northern Harrier in Lower Great Lakes / St. Lawrence Plain.
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 →
RandolphNEW-YORK22008
Alder CreekNEW-YORK21998
WaddingtonNEW-YORK21991
North PownalVERMONT22003
AusterlitzNEW-YORK12001
DuanesburgNEW-YORK12014
Oriskany FlsNEW-YORK11995
RomulusNEW-YORK12000
MacdougallNEW-YORK11989
TrumansburgNEW-YORK12000
OrleansNEW-YORK11985
RushvilleNEW-YORK12000
BranchportNEW-YORK12001
MendonNEW-YORK12000
Mt MorrisNEW-YORK12017
West SenecaNEW-YORK11990
CastileNEW-YORK12012
SheridanNEW-YORK11988
Cherry HillNEW-YORK11979
NashvilleNEW-YORK11997
St JohnsburgNEW-YORK12001
E YoungstownNEW-YORK12007
ByronNEW-YORK12007
ChurchvilleNEW-YORK12023
PenfieldNEW-YORK11994

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