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Species · BCR 36 · BBS 2026 Release · 1966–2025

Gull-billed Tern In Tamaulipan Brushlands

All regionsTamaulipan BrushlandsWetland birds

Gull-billed Tern in Tamaulipan Brushlands has declined: down 44% on the route-weighted index since 1985.

-44%Since 1985TrendPercent 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 →
4Routes 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 →
29YearsYears 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 →

No notable trend signals for Gull-billed Tern in Tamaulipan Brushlands. See the full index history below.

Gull-billed Tern In Tamaulipan Brushlands Population Forecast

If the recent trend holds, Gull-billed Tern in Tamaulipan Brushlands is projected to rise about 458% by 2030 — from 0.09 in 2025 to a central estimate of 0.51 (95% range 0.00–2.7). A 5-year backtest shows a typical error of ±549.8%, with 100% of held-out values landing inside the 95% band.

+458%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 →
0.51Projected 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 →
0.00–2.795% 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 →
±549.8%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, Gull-billed Tern in Tamaulipan Brushlands is projected to rise about 458% by 2030 — from 0.09 in 2025 to a central estimate of 0.51 (95% range 0.00–2.7). A 5-year backtest shows a typical error of ±549.8%, with 100% of held-out values landing inside the 95% band.19792030
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 →
20260.550.002.7
20270.540.002.7
20280.530.002.7
20290.520.002.7
20300.510.002.7

Routes In Tamaulipan Brushlands

Routes recording Gull-billed Tern in Tamaulipan Brushlands.
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 →
ProgresoTEXAS32007
KingsvilleTEXAS11987
RaymondvilleTEXAS12025
HeidelbergTEXAS12024

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