BirdAnalyst
Species · BCR 34 · BBS 2026 Release · 1966–2025

Tree Swallow In Sierra Madre Occidental

All regionsSierra Madre OccidentalAerial insectivores

Tree Swallow in Sierra Madre Occidental has fallen sharply: down 62% on the route-weighted index since 2008.

-62%Since 2008TrendPercent 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 →
14YearsYears 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 →

Tree Swallow has fallen sharply in Sierra Madre Occidental: down 62% on the route-weighted index since 2008.

Routes In Sierra Madre Occidental

Routes recording Tree Swallow in Sierra Madre Occidental.
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 →
MaineARIZONA42013
PinetopARIZONA22018
AlpineARIZONA22025
WilliamsARIZONA12025

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