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Lists:  MEX        
Number of species: 71

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Common Yellowthroat - Geothlypis trichas

Common Yellowthroat has a partial to incomplete preformative molt that replaces all median and greater coverts and can include the greater alula, up to all three tertials, some to all rectrices, and occasionally up to five inner secondaries and five outer primaries. The prealternate molts are absent to partial, mostly restricted to body feathers and up to three inner greater coverts. Molt limits can be subtle and by spring the differences in feather wear by age can be slight, so some intermediates are not reliably aged and should be considered M-FCU (AHY). All birds with black on the face are males, but some FCF (HY) males may lack black, and therefore those without black should generally be considered sex unknown rather than female.

Quick tips

  • Look at the face - only males have a black mask, but note some FCF (HY) males may also be entirely lacking black.
  • Examine the tail: uniformly narrow and pointed rectrices OR contrastingly fresh and broad replaced central rectrices indicate FCF/FCU (HY/SY), while uniformly broad and relatively rounded recrtices are typical of DCB/DCU (AHY/ASY) individuals, but can occasionally occur on FCF/FCU (HY/SY) birds that have undergone a particularly extensive preformative molt, including replacement of outer primaries.
  • Look at the primary coverts - on FCF/FCU (HY/SY) birds they are somewhat browner and more worn than the greater coverts, while on DCB/DCU (AHY/ASY) birds they are similar in colour and wear with the greater coverts; however, the contrast on FCF/FCU (HY/SY) birds can be quite subtle, and should not be used as the sole ageing criterion unless it is particularly distinct.

Species account prepared by McGill Bird Observatory (2016). 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: May - August)
Brownish wash above; buffy below; buffy wing bars
No images available yet
FCF - (HY: June - December; SY January - April)
Rectrices quite narrow and pointed or mixed with fresher, broader feathers (occasionally all replaced); primary coverts slightly browner than the greenish greater coverts; possible eccentric molt limits among the secondaries and primaries; hint of a black mask indicates (M); absence of it should be considered (U)
M
Thumbnail - MG2-2650-35311-Geothlypis_trichas_AOU_7_52-2382.jpg Thumbnail - MG2-2650-35311-Geothlypis_trichas_AOU_7_52-2380.jpg Thumbnail - MG2-2650-35311-Geothlypis_trichas_AOU_7_52-2381.jpg
F
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FCU - (SY: January - August)
Rectrices quite narrow and pointed or mixed with fresher, broader feathers (occasionally all replaced); primary coverts browner than the greenish greater coverts; possible eccentric molt limits among the secondaries and primaries; black mask present on males only
M
Thumbnail - MG2-2600-16005-Geothlypis_trichas_AOU_7_52-2400.jpg Thumbnail - MG2-2600-16005-Geothlypis_trichas_AOU_7_52-2398.jpg Thumbnail - MG2-2600-16005-Geothlypis_trichas_AOU_7_52-2399.jpg
F
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DCB - (AHY: June - December; ASY January - April)
Rectrices relatively broad and rounded; primary coverts with greenish edging, similar to greater coverts; black mask present on males only
No images available yet
DCU - (ASY: January - August)
Rectrices relatively broad and rounded; primary coverts with greenish edging, similar to greater coverts; black mask present on males only
M
Thumbnail - MG2-2600-16027-Geothlypis_trichas_AOU_7_52-2403.jpg Thumbnail - MG2-2600-16027-Geothlypis_trichas_AOU_7_52-2401.jpg Thumbnail - MG2-2600-16027-Geothlypis_trichas_AOU_7_52-2402.jpg
F
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Individuals in active molt

FPJ - (HY: May - August)
Similar to FCJ; some natal down remaining and/or juvenile flight feathers still growing in
U
Thumbnail - MG2-2600-16709-Geothlypis_trichas_AOU_7_52-2394.jpg Thumbnail - MG2-2600-16709-Geothlypis_trichas_AOU_7_52-2392.jpg Thumbnail - MG2-2600-16709-Geothlypis_trichas_AOU_7_52-2393.jpg
FPF - (HY: June - September)
Similar to FCF; median and greater coverts being replaced, and in some cases the greater alula, up to all tertials, some to all rectrices, and up five outer primaries and 5 inner secondaries
No images available yet
FPA - (HY: November - December; SY January - April)
Similar to FCF; some head and body feathers being replaced, as well as up to three inner greater coverts
No images available yet
SPB - (SY: June - September)
Flight feathers being replaced, with retained juvenile primaries, secondaries, and/or primary coverts distinctly pale brownish and very worn
No images available yet
DPB - (AHY: June - September)
Flight feathers being replaced, with retained primaries, secondaries, and/or primary coverts either distinctly adult (relatively dark, less worn) or intermediate
M
Thumbnail - MG2-2600-16704-Geothlypis_trichas_AOU_7_52-2391.jpg Thumbnail - MG2-2600-16704-Geothlypis_trichas_AOU_7_52-2389.jpg Thumbnail - MG2-2600-16704-Geothlypis_trichas_AOU_7_52-2390.jpg
F
Thumbnail - MG2-2500-65644-Geothlypis_trichas_AOU_7_52-2385.jpg Thumbnail - MG2-2500-65644-Geothlypis_trichas_AOU_7_52-2383.jpg Thumbnail - MG2-2500-65644-Geothlypis_trichas_AOU_7_52-2384.jpg
DPA - (AHY: November - December; ASY January - April)
Similar to DCB; some head and body feathers being replaced
No images available yet

Applicable unknown plumage/age classes

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