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Number of species: 79

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Field Sparrow - Spizella pusilla

Field Sparrow has a partial to incomplete molt that may not finish until after migration, and limited prealternate molts that are restricted to the face and throat and continue into summer. Most individuals can be aged reliably through molt limits. Although females are on average smaller and slightly duller in plumage, the 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), but note that both FCF/FCU (HY/SY) with an extensive preformative molt and DCB/DCU (AHY/ASY) individuals can have uniformly broad and rounded rectrices .
  • Examine the secondaries and primaries - most FCF/FCU (HY/SY) birds have at least a few fresh and dark replaced inner secondaries (and sometimes also outer primaries) that contrast with the paler central wing feathers; on DCB/DCU (AHY/ASY) birds the primaries and secondaries are uniform.
  • Check the primary coverts - they are relatively narrow, pale, and lacking edging on FCF/FCU (HY/SY) birds, but relatively broad, dark, and with rufous edging on DCB/DCU (AHY/ASY) birds.

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 - October)
Largely dull brown, with some faint streaking on the breast
No images available yet
FCF - (HY: July - December; SY January - May)
Rectrices all narrow and pointed, mixed with contrastingly fresh and broad rectrices, or occasionally all replaced; innermost secondaries and sometimes outermost primaries contrastingly dark and fresh; primary coverts narrow with little or no edging
U
Thumbnail - MG2-2440-72298-Spizella_pusilla_AOU_7_52-1844.jpg Thumbnail - MG2-2440-72298-Spizella_pusilla_AOU_7_52-1846.jpg Thumbnail - MG2-2440-72298-Spizella_pusilla_AOU_7_52-1845.jpg
FCU - (SY: April - September)
Rectrices all narrow and pointed, mixed with contrastingly fresh and broad rectrices, or occasionally all replaced; innermost secondaries and sometimes outermost primaries contrastingly dark and fresh; primary coverts narrow with little or no edging
U
Thumbnail - MG2-2460-40349-Spizella_pusilla_AOU_7_52-1847.jpg Thumbnail - MG2-2460-40349-Spizella_pusilla_AOU_7_52-1849.jpg Thumbnail - MG2-2460-40349-Spizella_pusilla_AOU_7_52-1848.jpg
DCB - (AHY: July - December; ASY January - May)
Rectrices uniformly broad and rounded; wing largely uniform in colour and wear, with secondaries and primary coverts only slightly lighter than greater coverts
No images available yet
DCU - (ASY: April - September)
Rectrices uniformly broad and rounded; wing largely uniform in colour and wear, with secondaries and primary coverts only slightly lighter than greater coverts
No images available yet

Individuals in active molt

FPJ - (HY: May - August)
Largely dull brown, with some faint streaking on the breast; some natal down remaining
No images available yet
FPF - (HY: July - November)
Similar to FCF; median and greater coverts and often also tertials and central rectrices being replaced
No images available yet
FPA - (SY: March - June)
Similar to FCF; some head and throat feathers being replaced
No images available yet
SPB - (SY: July - October)
Flight feathers being replaced, with retained juvenile flight feathers distinctly pale brown and very worn
No images available yet
DPB - (AHY: July - October)
Flight feathers being replaced, with retained flight feathers either distinctly adult (relatively dark, less worn, somewhat broad and rounded) or intermediate
No images available yet
DPA - (ASY: March - June)
Similar to DCB; some head and throat 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 July - October Undergoing preformative or prebasic molt, but cycle is not reliably distinguishable
M-FCF / UCU (FCF, SCB, DCB) U/AHY July - May In formative or basic plumage (molt completed), but cycle is not reliably distinguishable
M-FCA / UCA (FCA, DCA) AHY March - June In alternate plumage (molt completed), but cycle is not reliably distinguishable
M-FCU / UCU (FCU, DCU) AHY April - September In formative, basic, or alternate plumage (molt completed), but cycle and plumage are not reliably distinguishable

Number of species: 79

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