BirdAnalyst
Species · BBS 2025 Release · 1966–2024

Ruby-crowned Kinglet

RegulidaeForest birdsCorthylio calendula

Ruby-crowned Kinglet has surged: up 12× on the route-weighted index since 1968.

12×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 →
797RoutesSurvey 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 Ruby-crowned Kinglet

The Ruby-crowned Kinglet (Corthylio calendula) is a North American member of the Kinglets (Regulidae). In this analysis it is grouped with the forest birds.

Size
3.5–4.5 in long (9–11 cm) — a tiny songbird (typical for the family)
Habitat
Woodlands and forest edges, including wooded suburbs and parks.
Diet
Insects and spiders gleaned from foliage and bark, with seeds and berries in season.
Range
Recorded on 797 Breeding Bird Survey routes across 20 states, most concentrated in the Northern Rockies.
Family
Regulidae · Forest birds

Notable Ruby-crowned Kinglet TrendsNotable 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 increasecomputed 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 →

Ruby-crowned Kinglet has surged in surveyed states: up 12× on the route-weighted index since 1968.

Ruby-crowned Kinglet Population Forecast

If the recent trend holds, Ruby-crowned Kinglet is projected to rise about 64% by 2029 — from 0.95 in 2024 to a central estimate of 1.6 (95% range 1.1–2.0). A 5-year backtest shows a typical error of ±48%, with 20% of held-out values landing inside the 95% band.

+64%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 →
1.6Projected 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 →
1.1–2.095% 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 →
±48%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, Ruby-crowned Kinglet is projected to rise about 64% by 2029 — from 0.95 in 2024 to a central estimate of 1.6 (95% range 1.1–2.0). A 5-year backtest shows a typical error of ±48%, with 20% 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 →
20251.51.001.9
20261.51.01.9
20271.51.02.0
20281.51.12.0
20291.61.12.0

Where the Ruby-crowned Kinglet Is Detected

BBS routes recording Ruby-crowned Kinglet, sized by most recent count.

Ruby-crowned Kinglet Population Trend by State

Ruby-crowned Kinglet 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 →
Alaska+128%1978106
Arizona24×197515
California-75%197058
Colorado+823%197074
Idaho+249%197043
Maine-89%196863
Michigan+1%197135
Minnesota+2%196934
Montana+51%197052
Nevadainsufficient datan/a2
New Hampshire-23%196815
New Mexico+53%197114
New York-11%196827
Oregon-31%197063
South Dakota13×197512
Utah13×197448
Vermont-78%197115
Washington+72%197148
Wisconsin-65%196925
Wyoming+405%197048

Ruby-crowned Kinglet Population Trend by Region

Bird Conservation Regions are the ecological unit for trends.

Ruby-crowned Kinglet 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 →
BCR 2-61%19937
BCR 4+25%198265
Northern Pacific Rainforest16×197081
Great Basin+43%197266
Northern Rockies+33%1970154
Boreal Hardwood Transition-6%196988
Lower Great Lakes / St. Lawrence Plain-7%19727
Atlantic Northern Forest-61%1968112
Sierra Nevada-84%197225
Southern Rockies / Colorado Plateau17×1970137
Badlands and Prairies11×197520
Sierra Madre Occidental+656%197512

Ruby-crowned Kinglet Conservation Status

Our route-weighted index shows it up about 1117% 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.