BirdAnalyst
Species · BBS 2025 Release · 1966–2024

Black Tern

LaridaeWetland birdsChlidonias niger

Black Tern has declined: down 44% on the route-weighted index since 1968.

-44%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 →
305RoutesSurvey routesHow many standard-protocol BBS routes contributed counts. More routes means a steadier, better-sampled index; very thin coverage is suppressed.Full methodology →
58Years 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 Black Tern

The Black Tern (Chlidonias niger) 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 305 Breeding Bird Survey routes across 24 states, most concentrated in the Prairie Potholes.
Family
Laridae · Wetland birds

Notable Black 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 Black Tern. See the full index history below.

Black Tern Population Forecast

If the recent trend holds, Black Tern is projected to fall about 40% by 2029 — from 0.27 in 2024 to a central estimate of 0.16 (95% range 0.00–0.36). A 5-year backtest shows a typical error of ±27.1%, with 100% of held-out values landing inside the 95% band.

-40%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 →
0.16Projected 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 →
0.00–0.3695% 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 →
±27.1%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, Black Tern is projected to fall about 40% by 2029 — from 0.27 in 2024 to a central estimate of 0.16 (95% range 0.00–0.36). A 5-year backtest shows a typical error of ±27.1%, 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 →
20250.170.000.37
20260.170.000.37
20270.170.000.36
20280.170.000.36
20290.160.000.36

Where the Black Tern Is Detected

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

Black Tern Population Trend by State

Black 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 →
California-77%197319
Colorado-6%19934
Idaho-30%19783
Illinoisinsufficient datan/a5
Indianainsufficient datan/a1
Iowa+172%197115
Kansas-93%19735
Maineinsufficient datan/a1
Michigan-96%196817
Minnesota-84%196954
Missouriinsufficient datan/a1
Montana-71%197112
Nebraska-83%196916
Nevadainsufficient datan/a2
New Yorkinsufficient datan/a2
North Dakota+69%196938
Ohioinsufficient datan/a2
Oregon-95%197217
South Dakota-84%196928
Texasinsufficient datan/a3
Utah-80%19944
Washington-53%197012
Wisconsin-99%196842
Wyominginsufficient datan/a2

Black Tern Population Trend by Region

Bird Conservation Regions are the ecological unit for trends.

Black 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 →
Great Basin-92%197041
Northern Rockies-78%197115
Prairie Potholes-10%196987
Boreal Hardwood Transition-85%196933
Badlands and Prairies-63%196915
Central Mixed Grass Prairie-84%196915
Eastern Tallgrass Prairie-37%196922
Prairie Hardwood Transition-93%196856
Coastal California-75%19735

Black Tern Conservation Status

Our route-weighted index shows it down about 44% since 1968.

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