BirdAnalyst
Species · BCR 36 · BBS 2025 Release · 1966–2024

Brown-headed Cowbird In Tamaulipan Brushlands

All regionsTamaulipan BrushlandsGeneralists

Brown-headed Cowbird in Tamaulipan Brushlands has fallen sharply: down 51% on the route-weighted index since 1969.

-51%Since 1969TrendPercent 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 →
28Routes 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 →
57YearsYears 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 →

Brown-headed Cowbird has fallen sharply in Tamaulipan Brushlands: down 51% on the route-weighted index since 1969.

Brown-headed Cowbird In Tamaulipan Brushlands Population Forecast

If the recent trend holds, Brown-headed Cowbird in Tamaulipan Brushlands is projected to fall about 33% by 2029 — from 13 in 2024 to a central estimate of 8.9 (95% range 0.00–19). A 5-year backtest shows a typical error of ±35.2%, with 100% of held-out values landing inside the 95% band.

-33%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 →
8.9Projected 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 →
0.00–1995% 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 →
±35.2%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, Brown-headed Cowbird in Tamaulipan Brushlands is projected to fall about 33% by 2029 — from 13 in 2024 to a central estimate of 8.9 (95% range 0.00–19). A 5-year backtest shows a typical error of ±35.2%, with 100% of held-out values landing inside the 95% band.19672029
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 →
20259.90.0020
20269.70.0020
20279.40.0020
20289.20.0020
20298.90.0019

Routes In Tamaulipan Brushlands

Routes recording Brown-headed Cowbird 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 →
HondoTEXAS472024
RachalTEXAS222023
George WestTEXAS222024
CatarinaTEXAS222010
DilleyTEXAS152024
ProgresoTEXAS142011
Millett 2TEXAS142024
KingsvilleTEXAS122024
ZapataTEXAS111987
EncinalTEXAS112010
GuerraTEXAS112023
SejitaTEXAS112024
RaymondvilleTEXAS102024
Catarina 3TEXAS102024
LaredoTEXAS102023
Agua NuevaTEXAS92023
Mirando CityTEXAS82024
Encinal 2TEXAS82024
El IndioTEXAS72007
MillettTEXAS52012
Cavasara Cr.TEXAS52023
RandadoTEXAS42024
Catarina 2TEXAS42017
San YgnacioTEXAS31985
Pedro CreekTEXAS32010

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