BirdAnalyst
Species · BCR 33 · BBS 2025 Release · 1966–2024

Caspian Tern In Sonoran and Mojave Deserts

All regionsSonoran and Mojave DesertsWetland birds

Caspian Tern in Sonoran and Mojave Deserts has collapsed: down 90% on the route-weighted index since 1977.

-90%Since 1977TrendPercent 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 →
3Routes 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 →
30YearsYears 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 →

Caspian Tern has collapsed in Sonoran and Mojave Deserts: down 90% on the route-weighted index since 1977.

Caspian Tern In Sonoran and Mojave Deserts Population Forecast

If the recent trend holds, Caspian Tern in Sonoran and Mojave Deserts is projected to stay roughly flat through 2029, near 0.00 (95% range 0.00–0.64). A 5-year backtest shows a typical error of ±77.6%, with 100% of held-out values landing inside the 95% band.

n/aChange 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 →
0.00–0.6495% 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 →
±77.6%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, Caspian Tern in Sonoran and Mojave Deserts is projected to stay roughly flat through 2029, near 0.00 (95% range 0.00–0.64). A 5-year backtest shows a typical error of ±77.6%, with 100% of held-out values landing inside the 95% band.19742029
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 →
20250.000.000.64
20260.000.000.64
20270.000.000.64
20280.000.000.64
20290.000.000.64

Routes In Sonoran and Mojave Deserts

Routes recording Caspian Tern in Sonoran and Mojave Deserts.
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 →
Alamo RiverCALIFORNIA51986
BrawleyCALIFORNIA22012
NilandCALIFORNIA12024

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