PICTORIAL HIGHLIGHTS, LATE
FEBRUARY 2002
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Among the birds banded in the last two weeks was a second year (SY)
male House Finch with unusually weak coloration. It had only very
dull and restricted buffy yellow patches on its head and rump. The
plumage of this species is quite variable, ranging from dull yellow to
bright orange and dark red, depending on the diet and physiological condition
of the bird. Females not uncommonly can have colored rumps (and perhaps
a wash of color over their head), but only the males have the coloring
also concentrated on their throat, forehead, and supercillium.
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We banded our first probable spring migrant, an after second year (ASY)
male Red-winged Blackbird on 2/21; the Fox Sparrows listed in the table
above, also migrants, were banded on 2/27 and 2/28.
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As much as the arrival of Red-winged Blackbirds and Fox Sparrows is
a sure sign of early spring at Powdermill, so, too will be the departure
of our wintering American Tree Sparrows. Most will have left Powdermill
for points far north before the end of next month (well ahead of the vanguard
of returning, look-alike migrant Chipping Sparrows; in fact, the two species
barely overlap in their seasonal occurrence at Powdermill).
ATSPs have been very uncommon at Powdermill this winter--three out
of the four of them banded this winter (since last mid-December), plus
one banded in a previous winter, were recaptured on the last day of the
month, when it was very cold, windy, and snowy here. It often takes
a good winter storm to bring this hardy species into the feeders from the
surrounding weedy fields and brushy hedgerows.
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Our last photo highlight for the month is a
tip for banders, who know that the shape, size, color, and condition of
a bird's rectrices (tail feathers) can be an indicator of its age in species
that ordinarily retain their juvenal rectrices throughout their first year
of life. On average, juvenal rectrices will be more sharply pointed
at the tip, more worn, duller, and, sometimes, less distinctly patterned,
compared to the equivalent nonjuvenal (adult) feather. However, when
a young bird loses feathers accidentally and replaces them adventitiously
(outside the normal molt period), the replacement feathers will often have
"adult" characteristics. When such feathers are found alongside retained
juvenal feathers, it can make for a very useful direct comparison.
In the photo below of the spread tail of an immature (SY, or second
year) Dark-eyed Junco that we banded recently, the four mostly dark feathers
on the right (of the picture) are juvenal, being noticeably more worn,
browner, and more pointed compared to the three darker feathers on the
left. Note, also, that the the dark feather with the small white
spot on the right side of the photo (the bird's left rectrix number 4)
has much less white in it compared to its molted counterpart on the left
side of the photo (the bird's right rectrix number 4). Because
rectrices are naturally quite variable in shape, color, and degree of wear
even within age classes (as well as being rather prone to accidental loss
and replacement!), such differences should be used for helping to arrive
at a conclusion about the age of birds only in concert with other criteria
such as molt limits and degree of skull pneumatization.
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