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)