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Species · Michigan · BBS 2026 Release · 1966–2025

Mourning Warbler Population Trend in Michigan

All statesForest birds

Mourning Warbler in Michigan has surged: up 285% on the route-weighted index since 1968.

+285%Since 1968TrendPercent 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 →
74Routes 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 →
59YearsYears surveyedNumber of years with at least one standard-protocol run in this geography. A longer record makes the trend more reliable.Full methodology →

Notable Mourning Warbler Trends in MichiganNotable 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 →

Mourning Warbler has surged in Michigan: up 285% on the route-weighted index since 1968.

Mourning Warbler Population Forecast in Michigan

If the recent trend holds, Mourning Warbler in Michigan is projected to stay roughly flat through 2030, near 1.9 (95% range 0.54–3.2). A 5-year backtest shows a typical error of ±32.8%, with 100% of held-out values landing inside the 95% band.

+1%Change by 2030TrendPercent 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 →
1.9Projected 2030 indexProjected indexThe central forecast of the abundance index if the recent trend continues. A projection of the current trajectory, not a prediction.Full methodology →
0.54–3.295% 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 →
±32.8%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, Mourning Warbler in Michigan is projected to stay roughly flat through 2030, near 1.9 (95% range 0.54–3.2). A 5-year backtest shows a typical error of ±32.8%, with 100% of held-out values landing inside the 95% band.19662030
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 →
20261.80.503.2
20271.90.513.2
20281.90.523.2
20291.90.533.2
20301.90.543.2

Mourning Warbler Survey Routes in Michigan

Routes recording Mourning Warbler in Michigan.
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 →
Ned Lake1820251986
Pickford1520251973
Brocky Lake1020251980
Frederic920011983
Ontonagon720191969
Marenisco720191981
Herman720221983
Maple Grove720251967
Gibbs City620251979
Raco620251971
Imp Lake620191992
Ensign620102006
Bergland520221982
Sidnaw520251993
Mayfield520132000
Shingleton420251967
Gilchrist420211974
Hubbard Lake419961976
Bootjack320231967
Crystal Fls320251979
Ishpeming320251980
Isabella320061973
Irons319861986
Herron320132011
Scottville220231983

Mourning Warbler Population Trend in Other States

connecticutillinoisindianamainemarylandmassachusettsminnesotanew-hampshirenew-yorknorth-dakotaohiopennsylvaniavermontwest-virginiawisconsin

Source: USGS North American Breeding Bird Survey, retrieved 2026-08-14.