PHOTO LIBRARY

Black-throated Blue Warbler (Dendroica caerulescens)

JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC

common   fairly common   uncommon   rare   occasional   no records

 

QUICK TIPS: 1) Consider the upperparts - on males they are blue and black, and on females they are greenish 2) Examine the primary coverts - on HY/SY birds they are paler than greater coverts and lack edging, while on AHY/ASY birds they are uniform with the greater coverts and have distinct greenish (female) or bluish (male) edging 3) Look at the primaries - on HY/SY females there is little to no white (0-6 mm) extending beyond the primary coverts, on HY/SY males and AHY/ASY females there is a moderate amount of white (3-11 mm), and on AHY/ASY males there is considerable white (7-14 mm) 4) Look at the tail - on HY/SY females the outer rectrices are narrow and pointed with little or no white, on HY/SY males they are narrow and pointed with white patches, on AHY/ASY females they are relatively broad and rounded with indistinct white patches, and on AHY/ASY males they are relatively broad and rounded with large white patches

January - July:

ASY - M Blue and black upperparts; blue edging to primary coverts; extensive white patches on primaries       ASY - F Greenish upperparts; pale greenish edging to primary coverts; moderate white patches on primaries; rounded rectrices with indistinct whitish patches on outer feathers       SY - M Blue and black upperparts, no edging on primary coverts; moderate white patches on primaries       SY - F Greenish upperparts; no edging on primary coverts; white patches on primaries limited or absent; rectrices narrow and pointed, with indistinct whitish patches small or absent

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June - December:

AHY - M Blue and black upperparts; blue edging to primary coverts; extensive white patches on primaries AHY - F Greenish upperparts; pale greenish edging to primary coverts; moderate white patches on primaries; rounded rectrices with indistinct whitish patches on outer feathers HY - M Blue and black upperparts, no edging on primary coverts; moderate white patches on primaries HY - F Greenish upperparts; no edging on primary coverts; white patches on primaries limited or absent; rectrices narrow and pointed, with indistinct whitish patches small or absent

 

 

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Many after-hatch-year males can be recognized readily in the field by their uniformly blue and black upperparts and the very large white patch on the primaries.

Photo by Marcel Gahbauer, September 2005
 

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In addition to the extensive white patches on the primaries, this wing is distinctly that of an after-hatch-year male due to the bluish edging on the broad primary coverts, which are as dark overall as the adjacent greater coverts.

Photo by Marcel Gahbauer, September 2005
 

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The outer rectrices are broad and rounded, with a considerale amount of white.

Photo by Marcel Gahbauer, September 2005

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Hatch-year males can sometimes be easily recognized by having some greenish or grayish feathers on the back as in the first photo below, but others look superficially quite like after-hatch-year males, and the wing needs to be examined more closely to confirm age.

Photo by Marcel Gahbauer, September 2004

Photo by Marcel Gahbauer, August 2005
 

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Note the distinct contrast between the darker blue edged greater coverts and the paler primary coverts lacking edging.  Also, there is very little white on the secondaries, unlike the extensive white visible on after-hatch-year males.

Photo by Marcel Gahbauer, August 2005
 

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The rectrices are relatively narrow and pointed, but may have a similar amount of white to after-hatch-year males; the wing is much more reliable for ageing this species.

Photo by Marcel Gahbauer, August 2005

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Greenish upperparts and a minimal whitish patch on the primaries are typical of hatch-year females, but as there is considerable overlap between hatch-year and after-hatch-year females with respect to that patch, the wing and tail should be checked to verify age.

Photo by Marcel Gahbauer, September 2005
 

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Note the very limited extent of white beyond the primary coverts, and the generally dull appearance of the primary coverts, lacking any distinct edging.

Photo by Marcel Gahbauer, September 2005
 

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The narrow and pointed rectrices in the photo below are typical of a hatch-year bird.

Photo by Marcel Gahbauer, October 2005

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