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Number of species: 80

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Blue-headed Vireo - Vireo solitarius

Molt limits and condition of the rectrices are often sufficient for ageing Blue-headed Vireos, but especially in spring some individuals may appear intermediate, and multiple characteristics should be considered. Determination of sex is limited to brood patch / cloacal protuberance during the breeding season.

Although this account focuses on Blue-headed Vireo, it is believed to also apply to the closely related Cassin's and Plumbeous Vireos.

Quick Tips:

  • Examine the primary coverts, which on HY/SY birds are distinctly paler than the greater coverts, but on AHY/ASY both feather tracts are similarly dark.
  • Look at the outer rectrices - on HY/SY birds they are narrow and pointed, while on AHY/ASY birds they are more broad and rounded.
  • In fall, check the upper mandible lining - on HY birds it is whitish to pale gray, while on AHY birds it is dark gray to black.
  • Consider the shape and length of p10 relative to the primary coverts - on HY/SY birds it is rounded and somewhat longer than the primary coverts, while on AHY/ASY birds it is more pointed and shorter.

Species account prepared by McGill Bird Observatory

Click on any image below to bring up the side-by-side comparison tool.
Age / Sex  Image sets 
Hatch year / Unknown
Molt limit between fresh greater coverts and paler primary coverts; rectrices relatively narrow and pointed; roof of mouth whitish to pale gray.
Thumbnail - MG2-2091-71844-Vireo_solitarius_AOU_7_52-3621.jpg Thumbnail - MG2-2091-71844-Vireo_solitarius_AOU_7_52-3619.jpg Thumbnail - MG2-2091-71844-Vireo_solitarius_AOU_7_52-3620.jpg
After hatch year / Unknown
Primary and greater coverts, primaries, and secondaries uniformly dark; rectrices relatively broad and rounded; roof of mouth dark gray to black.
Thumbnail - MG2-2351-48688-Vireo_solitarius_AOU_7_52-3627.jpg Thumbnail - MG2-2351-48688-Vireo_solitarius_AOU_7_52-3625.jpg Thumbnail - MG2-2351-48688-Vireo_solitarius_AOU_7_52-3626.jpg
Second year / Unknown
Molt limit between fresh greater coverts and paler primary coverts; rectrices relatively narrow and pointed; sometimes one or more tertials contrastingly fresh.
Thumbnail - MG2-2221-20591-Vireo_solitarius_AOU_7_52-3612.jpg Thumbnail - MG2-2221-20591-Vireo_solitarius_AOU_7_52-3610.jpg Thumbnail - MG2-2221-20591-Vireo_solitarius_AOU_7_52-3611.jpg

Additional age / sex class descriptions

The following additional age / sex class descriptions were found for this species:
Age / Sex   Age / Sex class description
Juvenile / Unknown Similar to HY-U, but lacking molt limits, and somewhat more brownish overall.
After second year / Unknown Primary and greater coverts, primaries, and secondaries uniformly dark; rectrices relatively broad and rounded; sometimes one or two tertials contrastingly fresh.
Number of species: 80

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