North American Bird Bander

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Figure 1.  A formative-plumaged Eastern Towhee captured 8 Oct 2012 at Bluebonnet Swamp Nature Center in Baton Rouge, Louisiana, showing an eccentric molt-limit pattern among the primaries.

Figure 1 from the article Molt Limits Reveal Extent of Molt and Age in Black-capped Vireos.   During the breeding season, the molt limits of ASY, SY, and HY Black-capped Vireos differ. Labels used for individual feathers throughout this manuscript are shown in A. B-D show frequencies of replacement (%) of individual feathers for each age group. Feathers depicted in gray can be replaced whereas those shown in white are retained. The number in each replaced feather indicates the percent of the sample in which that feather was replaced.

Figure 2.   Feather replacement in the Black-capped Vireo during the first molt cycle is more extensive than previously known. Molt limits in this wing (marked by arrows) show an eccentric molt pattern in which the inner 5 tertials and secondaries, outer 7 primaries, and outer 5 primary coverts were replaced. This SY female was captured at Fort Hood, Texas on 2 July, 2010. The bird was just starting prebasic molt as indicated by its missing innermost primary. Note that the innermost tertial is barely visible protruding from beneath the photographer’s thumb, the two outer primaries are only slightly visible, and the outermost primary covert is not visible because the wing was not fully spread.  

Figure 3.  An example of an unusual alular molt limit in an SY Black-capped Vireo in which only the middle of the three quills was retained. The two images show the left and right alulae of a female captured at Fort Hood, Texas on 26 June, 2017.  This is the color version of Figure 3, left image, from the article Molt Limits Reveal Extent of Molt and Age in Black-capped Vireos.  

Figure 3.  An example of an unusual alular molt limit in an SY Black-capped Vireo in which only the middle of the three quills was retained. The two images show the left and right alulae of a female captured at Fort Hood, Texas on 26 June, 2017.    This is the color version of Figure 3,  right image, from the article Molt Limits Reveal Extent of Molt and Age in Black-capped Vireos.   

Figure 2A. I used tracings (A) made from photographs (B) to test the usefulness of primary covert shape alone for determining the age of Black-capped Vireos. The use of tracings rather than photographs served to conceal other age characters that were visible in the photographs like molt limits and the width of feather edgings. An SY male captured 20 April 2011 is depicted.  

Figure 2B. See description for Figure 2A.

Figure 3A. Primary covert shape is an unreliable indicator of age in the Black-capped Vireo. Many individuals have covert shapes opposite of the descriptions in Pyle (1997). For example, “A” shows a known fourth-year male with tapered, pointed coverts whereas “B” shows a known SY male (originally banded as a nestling) with relatively truncate coverts. These birds were recaptured and photographed on 17 May, 2010 and 12 May, 2009, respectively. 

 Figure 3B. Primary covert shape is an unreliable indicator of age in the Black-capped Vireo. Many individuals have covert shapes opposite of the descriptions in Pyle (1997). For example, “A” shows a known fourth-year male with tapered, pointed coverts whereas “B” shows a known SY male (originally banded as a nestling) with relatively truncate coverts. These birds were recaptured and photographed on 17 May, 2010 and 12 May, 2009, respectively.