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

Vesper Sparrow Population Trend in Delaware

All statesGrassland birds

Vesper Sparrow in Delaware has collapsed: down 81% on the route-weighted index since 1968.

-81%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 →
14Routes 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 →
47YearsYears surveyedNumber of years with at least one standard-protocol run in this geography. A longer record makes the trend more reliable.Full methodology →

Notable Vesper Sparrow Trends in DelawareNotable 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 →

Vesper Sparrow has collapsed in Delaware: down 81% on the route-weighted index since 1968.

Vesper Sparrow Population Forecast in Delaware

If the recent trend holds, Vesper Sparrow in Delaware is projected to fall about 100% by 2029 — from 0.20 in 2024 to a central estimate of 0.00 (95% range 0.00–0.60). A 5-year backtest shows a typical error of ±105.2%, 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 →
0.00–0.6095% 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 →
±105.2%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, Vesper Sparrow in Delaware is projected to fall about 100% by 2029 — from 0.20 in 2024 to a central estimate of 0.00 (95% range 0.00–0.60). A 5-year backtest shows a typical error of ±105.2%, 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 →
20250.000.000.60
20260.000.000.60
20270.000.000.60
20280.000.000.60
20290.000.000.60

Vesper Sparrow Survey Routes in Delaware

Routes recording Vesper Sparrow in Delaware.
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 →
Holleyville520041966
Milton320121966
Holleyville 2320092008
Mt Pleasant119991969
Wilmington119661966
Harrington119801966
Frederica119771967
Dover119781974
Frankford119761966
Lowes Xrds119701966
Bethany Bch119701967
Blackbird120192017
Georgetown120081996
Pepperbox 2120242024

Vesper Sparrow Population Trend in Other States

arizonacaliforniacoloradoconnecticutidahoillinoisindianaiowakansaskentuckymainemarylandmassachusettsmichiganminnesotamissourimontananebraskanevadanew-hampshirenew-jerseynew-mexiconew-yorknorth-carolinanorth-dakotaohiooklahomaoregonpennsylvaniasouth-dakotatennesseetexasutahvermontvirginiawashingtonwest-virginiawisconsinwyoming

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