BirdAnalyst
Species · BBS 2025 Release · 1966–2024

Willow Flycatcher

TyrannidaeAerial insectivoresEmpidonax traillii

Willow Flycatcher has increased: up 45% on the route-weighted index since 1968.

+45%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 →
1,780RoutesSurvey 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 Willow Flycatcher

The Willow Flycatcher (Empidonax traillii) is a North American member of the Tyrant Flycatchers (Tyrannidae). In this analysis it is grouped with the aerial insectivores.

Size
4.5–9 in long (12–23 cm) — a small to medium flycatcher (typical for the family)
Habitat
Open airspace over fields, water and towns; nests in cavities, earthen banks or on structures.
Diet
Flying insects caught on the wing.
Range
Recorded on 1,780 Breeding Bird Survey routes across 44 states, most concentrated in the Appalachian Mountains.
Family
Tyrannidae · Aerial insectivores

Notable Willow Flycatcher 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 Willow Flycatcher. See the full index history below.

Willow Flycatcher Population Forecast

If the recent trend holds, Willow Flycatcher is projected to rise about 15% by 2029 — from 0.67 in 2024 to a central estimate of 0.78 (95% range 0.56–0.99). A 5-year backtest shows a typical error of ±16.3%, with 100% of held-out values landing inside the 95% band.

+15%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 →
0.78Projected 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 →
0.56–0.9995% 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 →
±16.3%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, Willow Flycatcher is projected to rise about 15% by 2029 — from 0.67 in 2024 to a central estimate of 0.78 (95% range 0.56–0.99). A 5-year backtest shows a typical error of ±16.3%, 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 →
20250.780.560.99
20260.780.560.99
20270.780.560.99
20280.780.560.99
20290.780.560.99

Where the Willow Flycatcher Is Detected

BBS routes recording Willow Flycatcher, sized by most recent count.

Willow Flycatcher Population Trend by State

Willow Flycatcher 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 →
Alaskainsufficient datan/a2
Arizona+114%19985
Arkansasinsufficient datan/a8
California-52%197172
Colorado-61%197041
Connecticut+30%196917
Delaware+63%19787
Georgia-64%19775
Idaho+112%197153
Illinois+5%196899
Indiana-10%196866
Iowa+13%196934
Kansas+24%198111
Kentucky+98%197024
Maine-80%197930
Maryland+239%196844
Massachusetts+404%197025
Michigan-61%196870
Minnesota+125%196951
Missouri+120%197039
Montana-17%197065
Nebraska+236%197935
Nevada+39%199912
New Hampshire+205%197521
New Jersey+78%197028
New Mexico-50%197312
New York+113%1968113
North Carolina+0%197112
North Dakota+171%196948
Ohio+36%196884
Oklahoma-50%197510
Oregon-78%197098
Pennsylvania+96%1968118
Rhode Island+15%19874
South Dakota+179%196933
Tennessee-29%197015
Texasinsufficient datan/a1
Utah-22%197438
Vermont+100%197724
Virginia-65%196933
Washington-65%197093
West Virginia-23%196850
Wisconsin+114%196877
Wyoming-38%197053

Willow Flycatcher Population Trend by Region

Bird Conservation Regions are the ecological unit for trends.

Willow Flycatcher 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 →
Northern Pacific Rainforest-66%1970105
Great Basin-61%1970118
Northern Rockies-41%1970157
Prairie Potholes+144%196989
Boreal Hardwood Transition-68%197543
Lower Great Lakes / St. Lawrence Plain+67%196884
Atlantic Northern Forest+432%196889
Sierra Nevada-86%197413
Southern Rockies / Colorado Plateau+4%197079
Badlands and Prairies+279%197054
Central Mixed Grass Prairie+349%198323
Eastern Tallgrass Prairie-29%1968225
Prairie Hardwood Transition+19%1968152
Central Hardwoods+211%196871
Mississippi Alluvial Valley-47%19887
Appalachian Mountains+82%1968271
Piedmont+65%196854
New England / Mid-Atlantic Coast+275%196886
Coastal California+11%197229
Sonoran and Mojave Deserts-9%19738

Willow Flycatcher Conservation Status

Our route-weighted index shows it up about 44% since 1968. Aerial insectivores have fallen sharply across the continent, a decline widely linked to dwindling insect prey.

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