Ageing and sexing details:
|
JAN - JUL: after-second-year
unknown |
In most cases, ASY and SY White-crowned Sparrows are largely indistinguishable when perched, although some patterns better visible on the open wing may occasionally be seen with a good view. Sex can be identified only by brood patch or cloacal protuberance, and is therefore generally not possible to determine during migration.
Photo by Barbara Frei,
McGill Bird Observatory (QC), May 2008
ASY White-crowned Sparrows have relatively broad and rounded primary coverts that are fairly uniform in colour with the primaries, secondaries, and greater coverts.
Photo by Barbara Frei,
McGill Bird Observatory (QC), May 2008
The rectrices of ASY White-crowned Sparrows are broad and rounded, but beware that some SY birds may replace their entire tail by spring, therefore tail condition should not be used as the only ageing criteria for ASY. In both age classes, the central rectrices are often replaced during the prealternate molt, resulting in a colour contrast between the darker fresher feathers and the remaining paler rectrices (as in the photo below).
Photo by Barbara Frei,
McGill Bird Observatory (QC), May 2008
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OVERVIEW
|
JAN - JUL: second-year
unknown |
Occasionally a few brown/tan feathers
remaining in the crown can be used to recognize a second-year bird, but
in most cases the overall body plumage is of no help in determining age
in spring.
Photo by Marie-Anne Hudson,
McGill Bird Observatory (QC), May 2008
Photo by Marie-Anne Hudson,
McGill Bird Observatory (QC), May 2006
The primary coverts may be paler than the greater coverts, but as the photos below illustrate, the contrast may be subtle, showing up distinctly only in the third photo. Sometimes, as in the second photo, the outer primary coverts of SY birds are distinctly narrow and pointed, but as the first photo shows, this is also not always reliable. However, what is consistent is that in all cases, the primary coverts are uniform in colour with the primaries and secondaries, which as a block contrast with the greater coverts.
Photo by Marie-Anne Hudson,
McGill Bird Observatory (QC), May 2008
Photo by Marie-Anne Hudson,
McGill Bird Observatory (QC), May 2008
Photo by Marie-Anne Hudson,
McGill Bird Observatory (QC), May 2008
The rectrices tend to be relatively narrow and tapered toward the tip,
and showing a moderate to fair amount of wear. However, beare that there is considerable within-species variation for White-crowned Sparrows, and some SY birds may have replaced their entire tail by spring, therefore the rectrices are a useful indicator of SY only if they show distinct juvenal characteristics, as in the first two photos below.
Photo by Marie-Anne Hudson,
McGill Bird Observatory (QC), May 2008
Photo by Marie-Anne Hudson,
McGill Bird Observatory (QC), May 2008
Photo by Marie-Anne Hudson,
McGill Bird Observatory (QC), May 2008
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OVERVIEW
|
JUL - DEC: after-hatch-year
unknown |
In fall, the crown pattern alone is
sufficient to correctly age White-crowned Sparrows, as any individual
with a black/white pattern is an after-hatch-year bird. Note that
the pattern varies by subspecies; all the individuals banded to date at
MBO are of the Eastern race.
Photo by Marie-Anne Hudson,
McGill Bird Observatory (QC), October 2007
Photo by Marcel Gahbauer,
McGill Bird Observatory (QC), October 2005
Photo by Marcel Gahbauer,
McGill Bird Observatory (QC), October 2005
The primary coverts are fresh and dark, uniform in
colour and wear with the greater coverts.
Photo by Marie-Anne Hudson, McGill Bird Observatory (QC), October 2007
Photo by Marcel Gahbauer,
McGill Bird Observatory (QC), October 2005
The rectrices are
relatively broad and rounded at the tip, and generally in good
condition; as rectrix shape varies less in White-crowned Sparrow than
many other sparrows, there is no need to refer to it in fall when crown
pattern is a reliable indicator of age; however, doing so as a matter of
routine will help provide experience regarding the limited
within-species variation between HY/SY and AHY/ASY birds.
Photo by Marcel Gahbauer,
McGill Bird Observatory (QC), October 2005
Photo by James Junda,
McGill Bird Observatory (QC), September 2008
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OVERVIEW
|
JUL - DEC: hatch-year
unknown |
In fall, the crown pattern alone is
sufficient to correctly age White-crowned Sparrows, as any individual
with a brown/tan pattern is a hatch-year bird.
Photo by Marcel Gahbauer,
McGill Bird Observatory (QC), October 2005
Photo by Marie-Anne Hudson,
McGill Bird Observatory (QC), October 2007
Although the contrast is subtle, this photo shows
that the primary coverts (along with the primaries and secondaries) tend to be slightly paler and duller than the
greater coverts, which have been replaced in the preformative molt.
Photo by Marie-Anne Hudson,
McGill Bird Observatory (QC), October 2007
The rectrices are
relatively narrow and pointed at the tip, and generally showing some
wear; as rectrix shape varies less in White-crowned Sparrow than many
other sparrows, there is no need to refer to it in fall when crown
pattern is a reliable indicator of age; however, doing so as a matter of
routine will help provide experience regarding the limited
within-species variation between HY/SY and AHY/ASY birds.
Photo by Marcel Gahbauer,
McGill Bird Observatory (QC), October 2005
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OVERVIEW
