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Number of species: 79

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American Tree Sparrow - Spizelloides arborea

American Tree Sparrow has a partial preformative molt, and limited prealternate molts that are largely restricted to body feathers but can occasionally include tertials and central rectrices. Although molt limits and rectrix shape can be helpful, both are often subtle, and especially by spring a fair number of intermediates cannot be reliably aged and are best considered M-FCF (AHY). Sex of most individuals is reliably determined only via brood patch / cloacal protuberance during the breeding season.

Quick tips

  • Look at the tail - uniformly narrow and pointed rectrices OR contrastingly fresh and broad central rectrices are indicative of FCF/FCU (HY/SY), while uniformly broad and more rounded rectrices are typical of DCB/DCU (AHY/ASY).
  • Check the wing for molt limits - a slight contrast between darker/fresher greater coverts and tertials vs. the paler block of primary coverts, primaries, and secondaries is typical for FCF/FCU (HY/SY), while a wing more uniform in colour and wear suggests DCB/DCU (AHY/ASY).

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: July - October)
Rectrices all narrow and pointed; some streaking within the crown and upper breast
No images available yet
FCF - (HY: August - December; SY January - April)
Rectrices all narrow and pointed, or with contrastingly fresh and broad central rectrices; greater coverts and tertials slightly darker and fresher than primary coverts, primaries, and secondaries
U
Thumbnail - LD2-2631-61591-Spizella_arborea_AOU_7_52-4362.jpg Thumbnail - LD2-2631-61591-Spizella_arborea_AOU_7_52-4363.jpg Thumbnail - LD2-2631-61591-Spizella_arborea_AOU_7_52-4364.jpg
FCU - (SY: February - August)
Rectrices all narrow and pointed, or with contrastingly fresh and broad central rectrices; greater coverts and tertials slightly to considerably darker and fresher than primary coverts, primaries, and secondaries
U
Thumbnail - LG3-2631-50421-Spizella_arborea_AOU_7_52-3913.jpg Thumbnail - LG3-2631-50421-Spizella_arborea_AOU_7_52-3915.jpg Thumbnail - LG3-2631-50421-Spizella_arborea_AOU_7_52-3916.jpg Thumbnail - LG3-2631-50421-Spizella_arborea_AOU_7_52-3914.jpg
DCB - (AHY: July - December; ASY January - April)
Rectrices uniformly broad and rounded; wing largely uniform in colour and wear, with primary coverts only slightly lighter than greater coverts
U
Thumbnail - MR3-2521-59927-Spizella_arborea_AOU_7_52-2016.jpg

Thumbnail - LG3-NA_1648-Spizella_arborea_AOU_7_52-4475.jpg Thumbnail - LG3-NA_1648-Spizella_arborea_AOU_7_52-4476.jpg

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Thumbnail - MR3-2521-59927-Spizella_arborea_AOU_7_52-2020.jpg Thumbnail - MR3-2521-59927-Spizella_arborea_AOU_7_52-2021.jpg

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Thumbnail - MR3-2521-59927-Spizella_arborea_AOU_7_52-2019.jpg Thumbnail - MR3-2521-59927-Spizella_arborea_AOU_7_52-2017.jpg Thumbnail - MR3-2521-59927-Spizella_arborea_AOU_7_52-2018.jpg
DCU - (ASY: February - August)
Rectrices uniformly broad and rounded; wing largely uniform in colour and wear, with primary coverts only slightly lighter than greater coverts
U
Thumbnail - MH3-NA_385-Spizella_arborea_AOU_7_52-855.jpg

Thumbnail - MH3-NA_384-Spizella_arborea_AOU_7_52-854.jpg

Individuals in active molt

FPJ - (HY: July - September)
Rectrices all narrow and pointed; some streaking within the crown and upper breast; some natal down remaining
No images available yet
FPF - (HY: August - October)
Similar to FCF; median and greater coverts and tertials being replaced; sometimes central rectrices being replaced
No images available yet
FPA - (SY: February - May)
Similar to FCF; some body feathers being replaced, and occasionally central rectrices being replaced
No images available yet
SPB - (SY: July - September)
Flight feathers being replaced, with retained rectrices or outer primaries and primary coverts distinctly juvenile (pale brown and very worn)
No images available yet
DPB - (AHY: July - September)
Flight feathers being replaced, with retained rectrices or outer primaries and primary coverts either distinctly adult (relatively dark, less worn, somewhat broad and rounded) or intermediate
No images available yet
DPA - (ASY: February - May)
Similar to DCB; some body feathers being replaced, and occasionally central rectrices being replaced
No images available yet

Applicable unknown plumage/age classes

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