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Bicknell's Thrush - Catharus bicknelli

Bicknell's Thrush can generally be aged by a combination of molt limits and feather condition. HY/SY individuals are often easily recognized by retained juvenile greater coverts with pale shafts or tips, but since these can fade over time, some intermediates may be difficult to assess by spring. Sex is reliably determined only via brood patch / cloacal protuberance during the breeding season.

Bicknell's Thrush is quite similar to Gray-cheeked Thrush and should be identified with care in areas where both may occur. Bicknell's Thrush generally shows more yellow on the lower mandible and a greater contrast between the back and a rustier tail; consider also wing and tail measurements.

Quick Tips:

  • Look at the greater coverts - on HY/SY birds, the innermost two are generally longer, while the remainder are retained juvenile feathers and often show buffy-white shaft streaks. However, the absence of such streaks is not a reliable indicator of AHY/ASY, as some HY/SY birds may lack these markings
  • Consider the shape of the rectrices - they are narrow and relatively pointed on HY/SY birds, but broad and relatively rounded on AHY/ASY birds
  • Examine the outermost primary (p10) - on HY/SY birds it is broad, rounded, and 0-6 mm shorter than the primary coverts, while on AHY/ASY birds it is narrow, pointed, and 4-10 mm shorter than the primary coverts

Species account prepared by McGill Bird Observatory

  • Reference (2)
  • Supplemental (0)
  • Contributed (0)
Click on any image below to bring up the side-by-side comparison tool.
Age / Sex  Image sets 
Hatch year / Unknown
Inner 1-4 (often 2) greater coverts usually longer than others, while remainder may have pale shaft streaks; p10 relatively broad, rounded, long; rectrices narrow and pointed
Thumbnail - MG2-2571-20871-Catharus_bicknelli_AOU_7_52-2934.jpg Thumbnail - MG2-2571-20871-Catharus_bicknelli_AOU_7_52-2936.jpg Thumbnail - MG2-2571-20871-Catharus_bicknelli_AOU_7_52-2935.jpg
Date: Oct 2
After second year / Unknown
Wing uniform in appearance; outermost primary (p10) narrow, pointed, short; rectrices broad and rounded
Thumbnail - MG2-2201-54818-Catharus_bicknelli_AOU_7_52-2932.jpg Thumbnail - MG2-2201-54818-Catharus_bicknelli_AOU_7_52-2933.jpg Thumbnail - MG2-2201-54818-Catharus_bicknelli_AOU_7_52-2931.jpg
Date: May 27

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 Distinct pale spotting on the head, back, and wings
Second year / Unknown Inner 1-4 (often 2) greater coverts usually longer than others, while remainder may have pale shaft streaks; p10 relatively broad, rounded, long; rectrices narrow and pointed
After hatch year / Unknown Wing uniform in appearance; outermost primary (p10) narrow, pointed, short; rectrices broad and rounded
Number of species: 80

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