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Number of species: 79

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Ruby-crowned Kinglet - Regulus calendula

Ruby-crowned Kinglet has a partial preformative molt, and absent to limited prealternate molts that are difficult to detect. This species can be relatively difficult to age, as age-related differences in wing and tail patterns are often subtle; especially by spring, when a fair number of intermediates cannot be reliably aged and are best considered M-FCF (AHY), unless wing and tail cues clearly agree on a particular age. Individuals showing their ruby crown are easily recognized as males, but this feature is often concealed and females should be identified with greater caution.

Quick tips

  • Examine the crown - females lack red feathers, while males have a central red patch, but note that it may be well concealed.
  • Check the shape of the outer rectrices - on FCF/FCU (HY/SY) birds they are narrow and pointed, while on DCB/DCU (AHY/ASY) birds they tend to be more broad and rounded; however, there are many intermediates that are difficult to classify.
  • Look at the primary coverts - on many FCF/FCU (HY/SY) birds they are narrow and pointed (with minimal green edging remaining by spring), while on DCB/DCU (AHY/ASY) birds they tend to be more broad and rounded (with distinct green edging retained through spring).
  • Examine the inner greater coverts - on a small minority of FCF/FCU (HY/SY) birds up to three feathers are replaced and are slightly longer and darker than the adjacent older feathers, but uniform greater coverts can be seen at all ages.

Species account prepared by McGill Bird Observatory (2018). Last updated by Marcel Gahbauer (Mar 2022)

The molt categories displayed below may be filtered by month.

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Click on any image below to bring up the side-by-side comparison tool.

Individuals not in molt

FCJ - (HY: June - August)
Buffy wing bars, orange gape, uniformly brownish-green crown
No images available yet
FCF - (HY: July - December; SY January - March)
Primary coverts and rectrices narrow and pointed; up to three inner greater coverts sometimes longer and darker; crown uniformly greenish (F) or with a central red patch, often largely concealed (M)
M
Thumbnail - MG2-2550-81089-Regulus_calendula_AOU_7_52-3870.jpg Thumbnail - MG2-2550-81089-Regulus_calendula_AOU_7_52-3868.jpg Thumbnail - MG2-2550-81089-Regulus_calendula_AOU_7_52-3869.jpg
F
Thumbnail - MG2-2180-49950-Regulus_calendula_AOU_7_52-3873.jpg Thumbnail - MG2-2180-49950-Regulus_calendula_AOU_7_52-3871.jpg Thumbnail - MG2-2180-49950-Regulus_calendula_AOU_7_52-3872.jpg
FCU - (SY: February - August)
Primary coverts and rectrices narrow and pointed; up to three inner greater coverts sometimes longer and darker; crown uniformly greenish (F) or with a central red patch, often largely concealed (M)
No images available yet
DCB - (AHY: July - December; ASY January - March)
Primary coverts and rectrices relatively broad and rounded; coverts uniform in colour and wear; crown uniformly greenish (F) or with a central red patch, often largely concealed (M)
M
Thumbnail - MG2-2630-68718-Regulus_calendula_AOU_7_52-3876.jpg Thumbnail - MG2-2630-68718-Regulus_calendula_AOU_7_52-3874.jpg Thumbnail - MG2-2630-68718-Regulus_calendula_AOU_7_52-3875.jpg
F
Thumbnail - MG2-2550-81202-Regulus_calendula_AOU_7_52-3882.jpg Thumbnail - MG2-2550-81202-Regulus_calendula_AOU_7_52-3880.jpg Thumbnail - MG2-2550-81202-Regulus_calendula_AOU_7_52-3881.jpg
DCU - (ASY: February - August)
Primary coverts and rectrices relatively broad and rounded; coverts uniform in colour and wear; crown uniformly greenish (F) or with a central red patch, often largely concealed (M)
M
Thumbnail - MG2-2520-48614-Regulus_calendula_AOU_7_52-3864.jpg Thumbnail - MG2-2520-48614-Regulus_calendula_AOU_7_52-3862.jpg Thumbnail - MG2-2520-48614-Regulus_calendula_AOU_7_52-3863.jpg
F
Thumbnail - MG2-2530-59585-Regulus_calendula_AOU_7_52-3867.jpg Thumbnail - MG2-2530-59585-Regulus_calendula_AOU_7_52-3865.jpg Thumbnail - MG2-2530-59585-Regulus_calendula_AOU_7_52-3866.jpg

Individuals in active molt

FPJ - (HY: June - August)
Buffy wing bars, orange gape, uniformly brownish-green crown; some natal down feathers remaining
No images available yet
FPF - (HY: July - September)
Lesser and/or median and/or inner greater coverts being replaced; red central crown feathers growing in (M)
No images available yet
FPA - (SY: February - April)
Primary coverts and rectrices narrow and pointed; up to three inner greater coverts sometimes longer and darker; some body feathers being replaced
No images available yet
SPB - (SY: July - August)
Flight feathers being replaced, with at least some retained juvenile primary coverts or rectrices that are distinctly pale brownish, worn, and narrow and pointed
No images available yet
DPB - (AHY: July - August)
Flight feathers being replaced, with retained feathers either distinctly adult (relatively dark, less worn, somewhat broad and rounded) or intermediate
No images available yet
DPA - (ASY: February - April)
Primary coverts and rectrices relatively broad and rounded; coverts uniform in colour and wear; some body feathers in active replacement
No images available yet

Applicable unknown plumage/age classes

Molt classes Age Months Key traits
M-FPF / UPU (FPF, SPB, DPB) U July - August Undergoing preformative or prebasic molt, but cycle is not reliably distinguishable
M-FCF / UCU (FCF, SCB, DCB) U/AHY July - March In formative or basic plumage (molt completed), but cycle is not reliably distinguishable
M-FPA / UPA (FPA, DPA) AHY February - April Undergoing prealternate molt, but cycle is not reliably distinguishable
M-FCU / UCU (FCU, DCU) AHY February - August In formative, basic, or alternate plumage (molt completed), but cycle and plumage are not reliably distinguishable

Number of species: 79

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