BirdAnalyst
Species · New Jersey · BBS 2025 Release · 1966–2024

Common Tern Population Trend in New Jersey

All statesWetland birds

Common Tern in New Jersey has collapsed: down 87% on the route-weighted index since 1981.

-87%Since 1981TrendPercent 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 →
5Routes 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 →
34YearsYears surveyedNumber of years with at least one standard-protocol run in this geography. A longer record makes the trend more reliable.Full methodology →

Notable Common Tern Trends in New JerseyNotable 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 →

Common Tern has collapsed in New Jersey: down 87% on the route-weighted index since 1981.

Common Tern Population Forecast in New Jersey

If the recent trend holds, Common Tern in New Jersey is projected to fall about 68% by 2029 — from 0.10 in 2024 to a central estimate of 0.03 (95% range 0.00–0.51). A 5-year backtest shows a typical error of ±27.2%, with 100% of held-out values landing inside the 95% band.

-68%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 →
0.03Projected 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 →
0.00–0.5195% 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 →
±27.2%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, Common Tern in New Jersey is projected to fall about 68% by 2029 — from 0.10 in 2024 to a central estimate of 0.03 (95% range 0.00–0.51). A 5-year backtest shows a typical error of ±27.2%, with 100% of held-out values landing inside the 95% band.19792029
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 →
20250.090.000.57
20260.070.000.56
20270.060.000.54
20280.040.000.53
20290.030.000.51

Common Tern Survey Routes in New Jersey

Routes recording Common Tern in New Jersey.
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 →
Six Points220141992
Ocean City220241979
Winslow119911991
Pedricktown 2120212021
Villas119791979

Common Tern Population Trend in Other States

alabamaalaskaconnecticutdelawarefloridaidahoindianalouisianamainemarylandmassachusettsmichiganminnesotamontananew-yorknorth-carolinanorth-dakotaohiorhode-islandsouth-dakotatexasvermontvirginiawashingtonwisconsinwyoming

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