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Number of species: 71

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Chestnut-sided Warbler - Setophaga pensylvanica

Chestnut-sided Warbler has a partial preformative molt, and partial prealternate molts that include some to all greater coverts, and occasionally up to two tertials. Older females and younger males can overlap in aspects of appearance, making it important to determine age before sex; for some intermediate individuals, age and especially sex may not be reliably determined.

Quick tips

  • Check the primary coverts - on FCF/FCA (HY/SY) individuals they are brownish-gray with little or no edging, contrasting with darker and fresher greater coverts, whereas on DCB/DCA (AHY/ASY) individuals the primary and greater coverts are more uniformly dark, with distinct edging.
  • Look at the tail - the outer rectrices tend to be relatively narrow and tapered to a point on FCF/FCA (HY/SY) birds, but more broad and rounded on DCB/DCA (AHY/ASY) birds.
  • Examine the flanks - DCB/DCA (AHY) males have distinct and extensive chestnut markings, somewhat more so than on FCA (SY) males, while DCB/DCA (AHY) females, FCA (SY) females, and some FCF (HY) males have limited chestnut, and FCF (HY) females lack chestnut entirely.
  • In alternate plumage (spring/summer), look at the lores and moustache - on males they are black, while on females they are largely grayish.

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: June - July)
Brownish-olive upperparts, dingy white underparts; yellowish wing bars
No images available yet
FCF - (HY: June - December; SY January - April)
Primary coverts, primaries, and secondaries distinctly duller and paler than greater coverts; rectrices usually somewhat narrow and pointed with white limited to outermost 2-3 feathers; flanks lacking (U) or with a hint of chestnut (M)
M
Thumbnail - MG2-2410-92951-Setophaga_pensylvanica_AOU_7_52-2423.jpg Thumbnail - MG2-2410-92951-Setophaga_pensylvanica_AOU_7_52-2421.jpg Thumbnail - MG2-2410-92951-Setophaga_pensylvanica_AOU_7_52-2422.jpg
F
Thumbnail - MG2-2410-92346-Setophaga_pensylvanica_AOU_7_52-2420.jpg Thumbnail - MG2-2410-92346-Setophaga_pensylvanica_AOU_7_52-2418.jpg Thumbnail - MG2-2410-92346-Setophaga_pensylvanica_AOU_7_52-2419.jpg
FCA - (SY: February - September)
Primary coverts, primaries, and secondaries brownish, contrasting strongly with dark gray (F) to blackish (M) greater coverts; rectrices usually somewhat narrow and pointed with white limited to outermost 2-3 feathers; flanks with faint (F) or moderately distinct (M) chestnut patches; lores and moustache grayish (F) or blackish (M)
M
Thumbnail - MG2-2520-48683-Setophaga_pensylvanica_AOU_7_52-2921.jpg Thumbnail - MG2-2520-48683-Setophaga_pensylvanica_AOU_7_52-2919.jpg Thumbnail - MG2-2520-48683-Setophaga_pensylvanica_AOU_7_52-2920.jpg
F
Thumbnail - MG2-2530-54739-Setophaga_pensylvanica_AOU_7_52-2429.jpg Thumbnail - MG2-2530-54739-Setophaga_pensylvanica_AOU_7_52-2427.jpg Thumbnail - MG2-2530-54739-Setophaga_pensylvanica_AOU_7_52-2428.jpg
DCB - (AHY: June - December; ASY January - April)
Primary coverts, primaries, and secondaries contrasting only slightly with greater coverts; rectrices usually somewhat broad and rounded, with white on 2-3 (F) or 3-4 (M) outermost feathers; flanks with a small (F) to fairly extensive (M) chestnut patches
M
Thumbnail - MG2-2520-48195-Setophaga_pensylvanica_AOU_7_52-2409.jpg Thumbnail - MG2-2520-48195-Setophaga_pensylvanica_AOU_7_52-2407.jpg Thumbnail - MG2-2520-48195-Setophaga_pensylvanica_AOU_7_52-2408.jpg
F
Thumbnail - MG2-2410-92342-Setophaga_pensylvanica_AOU_7_52-2415.jpg Thumbnail - MG2-2410-92342-Setophaga_pensylvanica_AOU_7_52-2413.jpg Thumbnail - MG2-2410-92342-Setophaga_pensylvanica_AOU_7_52-2414.jpg
DCA - (ASY: February - September)
Primary coverts, primaries, and secondaries grayish, contrastinging moderately with dark gray (F) to blackish (M) greater coverts; rectrices usually somewhat broad and rounded, with white on 2-3 (F) or 3-4 (M) outermost feathers; flanks with moderate (F) to substantial (M) chestnut patches; lores and moustache gray (F) or black (M)
No images available yet

Individuals in active molt

FPJ - (HY: June - July)
Similar to FCJ; some natal down remaining and/or juvenile flight feathers still growing in
No images available yet
FPF - (HY: June - September)
Similar to FCF; body feathers, some to all median coverts, and up to four inner greater coverts being replaced
U
Thumbnail - MG2-2530-59603-Setophaga_pensylvanica_AOU_7_52-2426.jpg Thumbnail - MG2-2530-59603-Setophaga_pensylvanica_AOU_7_52-2424.jpg Thumbnail - MG2-2530-59603-Setophaga_pensylvanica_AOU_7_52-2425.jpg
FPA - (SY: January - May)
Similar to FCA; some to all greater coverts and occasionally one of the tertials being replaced
No images available yet
SPB - (SY: June - October)
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 - October)
Flight feathers being replaced, with retained primaries, secondaries, and/or primary coverts either distinctly adult (generally grayish, less worn) or intermediate
No images available yet
DPA - (ASY: January - May)
Similar to DCA; some to all greater coverts and occasionally one of the tertials 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 January - May Undergoing prealternate molt, but cycle is not reliably distinguishable
M-FCA / UCA (FCA, DCA) AHY February - September In alternate plumage (molt completed), but cycle is not reliably distinguishable