BirdAnalyst
Species · South Carolina · BBS 2025 Release · 1966–2024

Boat-tailed Grackle Population Trend in South Carolina

All statesGeneralists

Boat-tailed Grackle in South Carolina has fallen sharply: down 62% on the route-weighted index since 1968.

-62%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 →
6Routes 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 →
39YearsYears surveyedNumber of years with at least one standard-protocol run in this geography. A longer record makes the trend more reliable.Full methodology →

Notable Boat-tailed Grackle Trends in South CarolinaNotable 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 →

Boat-tailed Grackle has fallen sharply in South Carolina: down 62% on the route-weighted index since 1968.

Boat-tailed Grackle Population Forecast in South Carolina

If the recent trend holds, Boat-tailed Grackle in South Carolina is projected to fall about 100% by 2029 — from 0.57 in 2024 to a central estimate of 0.00 (95% range 0.00–1.3). A 5-year backtest shows a typical error of ±67.8%, 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 →
0.00–1.395% 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 →
±67.8%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, Boat-tailed Grackle in South Carolina is projected to fall about 100% by 2029 — from 0.57 in 2024 to a central estimate of 0.00 (95% range 0.00–1.3). A 5-year backtest shows a typical error of ±67.8%, with 100% of held-out values landing inside the 95% band.19662029
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 →
20250.080.001.3
20260.060.001.3
20270.040.001.3
20280.020.001.3
20290.000.001.3

Boat-tailed Grackle Survey Routes in South Carolina

Routes recording Boat-tailed Grackle in South Carolina.
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 →
Johns Isle4119791966
Kiawah Island1020241998
Hardeeville220241972
Adams Run120092004
Holly Hill119941994
Dale120012001

Boat-tailed Grackle Population Trend in Other States

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