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Number of species: 79

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Black-throated Blue Warbler - Setophaga caerulescens

Black-throated Blue Warbler has a partial preformative molt, while prealternate molts are absent to limited and difficult to detect. Males and females have distinctly different plumages at all ages. Ageing of females may require closer examination of the wing and/or tail than for males, but can still be done with confidence in most cases.

Quick tips

  • Consider the upperparts - on males they are blue and black, and on females they are greenish.
  • Examine the primary coverts - on FCF/FCU (HY/SY) birds they are paler and duller than greater coverts and lack edging, while on DCB/DCU (AHY/ASY) birds they are uniform with the greater coverts and have greenish (female) or distinct bluish (male) edging.
  • Look at the primaries - on DCB/DCU (AHY/ASY) males there is considerable white extending beyond the primary coverts (7-14 mm), on FCF/FCU (HY/SY) males and DCB/DCU (AHY/ASY) females there is a moderate amount of white (3-11 mm), and on FCF/FCU (HY/SY) females there is little to no white (0-6 mm).
  • Look at the tail - on DCB/DCU (AHY/ASY) males they are relatively broad and rounded with large white patches, on DCB/DCU (AHY/ASY) females they are similar in shape but with indistinct white patches; on FCF/FCU (HY/SY) males they are narrow and pointed with moderate white patches, while on FCF/FCU (HY/SY) females they are similar in shape but have little or no white.

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 - August)
Similar to FCF but somewhat more brownish above
No images available yet
FCF - (HY: June - December; SY January - April)
Rectrices relatively narrow and pointed; wings and upperparts uniformly dull green with white spots on primaries small to absent (F) or upperparts greenish-blue with small white spots on primaries and primary coverts contrastingly brown versus blue-edged greater coverts (M)
M
Thumbnail - MG2-2500-68109-Setophaga_caerulescens_AOU_7_52-2266.jpg Thumbnail - MG2-2500-68109-Setophaga_caerulescens_AOU_7_52-2268.jpg Thumbnail - MG2-2500-68109-Setophaga_caerulescens_AOU_7_52-2267.jpg
F
Thumbnail - MG2-2440-72242-Setophaga_caerulescens_AOU_7_52-2275.jpg Thumbnail - MG2-2440-72242-Setophaga_caerulescens_AOU_7_52-2277.jpg Thumbnail - MG2-2440-72242-Setophaga_caerulescens_AOU_7_52-2276.jpg
FCU - (SY: February - August)
Rectrices relatively narrow and pointed; wings and upperparts uniformly dull green with white spots on primaries small to absent (F) or upperparts greenish-blue with small white spots on primaries and primary coverts contrastingly brown versus blue-edged greater coverts (M)
M
Thumbnail - MG2-2600-16004-Setophaga_caerulescens_AOU_7_52-2254.jpg Thumbnail - MG2-2600-16004-Setophaga_caerulescens_AOU_7_52-2256.jpg Thumbnail - MG2-2600-16004-Setophaga_caerulescens_AOU_7_52-2255.jpg
DCB - (AHY: June - December; ASY January - April)
Rectrices relatively broad and rounded; wings and upperparts largely dull green but with distinct white spots on primaries (F) or upperparts blue with large white spots on primaries and primary coverts dark with bluish edging (M)
M
Thumbnail - MG2-2440-72112-Setophaga_caerulescens_AOU_7_52-2260.jpg Thumbnail - MG2-2440-72112-Setophaga_caerulescens_AOU_7_52-2262.jpg Thumbnail - MG2-2440-72112-Setophaga_caerulescens_AOU_7_52-2261.jpg
F
Thumbnail - MG2-2440-72208-Setophaga_caerulescens_AOU_7_52-2263.jpg Thumbnail - MG2-2440-72208-Setophaga_caerulescens_AOU_7_52-2265.jpg Thumbnail - MG2-2440-72208-Setophaga_caerulescens_AOU_7_52-2264.jpg
DCU - (ASY: February - August)
Rectrices relatively broad and rounded; wings and upperparts largely dull green but with distinct white spots on primaries (F) or upperparts blue with large white spots on primaries and primary coverts dark with bluish edging (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 - August)
Similar to FCF; median and most to all greater coverts, and sometimes one or two tertials being replaced
No images available yet
FPA - (SY: January - May)
Similar to FCA; some body feathers being replaced
No images available yet
SPB - (SY: July - September)
Flight feathers being replaced, with retained juvenile primaries, secondaries, and/or primary coverts distinctly pale brownish and worn
No images available yet
DPB - (AHY: July - September)
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 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 July - August 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-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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