BirdAnalyst
Species · BBS 2025 Release · 1966–2024

Sandwich Tern

LaridaeWetland birdsThalasseus sandvicensis

Sandwich Tern has surged: up 123% on the route-weighted index since 1979.

+123%Since 1979TrendPercent 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 →
19RoutesSurvey routesHow many standard-protocol BBS routes contributed counts. More routes means a steadier, better-sampled index; very thin coverage is suppressed.Full methodology →
36Years SurveyedYears surveyedNumber of years with at least one standard-protocol run in this geography. A longer record makes the trend more reliable.Full methodology →

About the Sandwich Tern

The Sandwich Tern (Thalasseus sandvicensis) is a North American member of the Gulls, Terns & Skimmers (Laridae). In this analysis it is grouped with the wetland birds.

Size
8.5–31.5 in long (22–80 cm) — a long-winged waterbird (typical for the family)
Habitat
Marshes, ponds, lakeshores and other freshwater wetlands.
Diet
Aquatic invertebrates, small fish, frogs and plant matter.
Range
Recorded on 19 Breeding Bird Survey routes across 6 states, most concentrated in the Southeastern Coastal Plain.
Family
Laridae · Wetland birds

Notable Sandwich Tern TrendsNotable 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 Sandwich Tern. See the full index history below.

Sandwich Tern Population Forecast

If the recent trend holds, Sandwich Tern is projected to stay roughly flat through 2029, near 0.01 (95% range 0.00–0.03). A 5-year backtest shows a typical error of ±67.8%, with 40% 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 →
0.01Projected 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 →
0.00–0.0395% 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, Sandwich Tern is projected to stay roughly flat through 2029, near 0.01 (95% range 0.00–0.03). A 5-year backtest shows a typical error of ±67.8%, with 40% of held-out values landing inside the 95% band.19702029
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 →
20250.010.000.03
20260.010.000.03
20270.010.000.03
20280.010.000.03
20290.010.000.03

Where the Sandwich Tern Is Detected

BBS routes recording Sandwich Tern, sized by most recent count.

Sandwich Tern Population Trend by State

Sandwich Tern population trend by state.
TrendPercent 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 →Baseline yearThe first year of the smoothed window the trend is measured from. An earlier baseline means a longer record stands behind the number.Full methodology →Survey routesHow many standard-protocol BBS routes contributed counts. More routes means a steadier, better-sampled index; very thin coverage is suppressed.Full methodology →
Alabama-57%19846
Floridainsufficient datan/a6
Louisianainsufficient datan/a1
North Carolinainsufficient datan/a2
Texasinsufficient datan/a3
Virginiainsufficient datan/a1

Sandwich Tern Population Trend by Region

Bird Conservation Regions are the ecological unit for trends.

Sandwich Tern population trend by Bird Conservation Region.
TrendPercent 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 →Baseline yearThe first year of the smoothed window the trend is measured from. An earlier baseline means a longer record stands behind the number.Full methodology →Survey routesHow many standard-protocol BBS routes contributed counts. More routes means a steadier, better-sampled index; very thin coverage is suppressed.Full methodology →
Southeastern Coastal Plain-36%197912
Gulf Coastal Prairie+469%20104

Sandwich Tern Conservation Status

Our route-weighted index shows it up about 123% since 1979.

Source: USGS North American Breeding Bird Survey, retrieved 2026-05-22. Trend is a route-weighted relative-abundance index, not an absolute population.