POWDERMILL NATURE RESERVE
June 24-30, 2002:
Four of the six OVENs
were banded today on 6/30--three out of these four showed no signs yet
of beginning prebasic molt and one was in the very earliest stage, having
just recently dropped its first and second primaries. As we have
mentioned here before, it is very common for some kinds of forest nesting
songbirds at Powdermill to leave their woodland breeding habitats shortly
after completion of nesting (often in the company of their fledglings)
and move into the dense riparian and upland shrub- scrub habitats where
our nets are located. These more densely vegtated habitats not only
provide additional cover and food for the inexperienced fledglings, but
also a protected place for adults to undergo their annual wing molt, which,
at its height, can reduce their flight ability and, consequently, their
ability to escape predators.
In order to study wing molt in a quantitative
way, banders often assign a numerical rank (0-5) to each flight feather.
An unmolted feather receives a score of "0;" a feather just dropped or
in "pin" scores a "1;" in the "brush" stage up to 1/3 grown rates
a "2;" from 1/3 to 2/3 grown is a "3;" from 2/3 to almost fully
grown is a "4;" freshly molted and fully grown scores "5." Prior
to the onset of molt, birds have a total molt score of zero.
At molt completion (all feathers scoring a "5"), for birds with nine
primaries and nine secondaries, the total molt score is 90. By scoring
molt in this way, the timing and rate of molt within and between species
can be easily compared.
Many species at Powdermill, including most
are well along with their molt now. The photos below show two different
second year (SY) male American Redstarts
caught on 6/30 that were molting from their female-like gray and yellow
plumage to their definitive black and orange. The top bird's molt
score was 12, while the bottom bird scored a 24.
By way of comparison, the molting Yellow
Warbler pictured below had a molt score of
20--a total of nine feathers, the inner six primaries and the inner three
secondaries (also called the tertials) were actively molting. This
molt sequence--inner primaries first (beginning with primary 1 and proceeding
outward) , followed by the tertials (inner secondaries 7-9; usually sec.
8 first, followed by 7 & 9) and, lastly, by the outer secondaries (beginning
with secondary 1 and progressing inward toward the tertials)--is the characteristic
molt sequence of most adult passerines.
At the same time that we are catching many motley
(i.e., molty) adults (some of which, like the SY-M AMRE below, are hardly
we are also catching juveniles of many local
breeding species. When these are still clad mostly in their fluffy
juvenal plumage, they can be puzzling as well! Thankfully, most species
begin molting out of this often nondescript plumage within days after fledging.
Do you know the species of warbler pictured below? (Answer at the
bottom of this page)
June 3-23, 2002:
During the period, we banded an SY male Scarlet
Tanager that had an unusual plumage.
To begin with, its prealternate body molt evidently was not complete--the
bird still had a considerable number of retained (and worn) yellow-olive
basic body feathers. Even those body feathers that had been replaced
during the prealternate molt were orange rather than the usual scarlet
But even more unusual were the bird's scattered
white or partly white wing feathers. All three outer juvenal primaries
on the right wing, as well as one juvenal primary covert, were entirely
white. They were noticeably much more worn than the neighboring
wing feathers. This is because they lacked the melanin pigments that
strengthen feathers and make them more resistant to abrasion. In
the closeup lower photo, compare the degree of wear between the tips of
the white juvenal outer primaries 7-9, the normally pigmented (much fresher
and probably adventitiously replaced) primary no. 6, and even compared
to retained juvenal primary no. 5. The bird's left wing showed
only slight loss of pigmentation at the very tips of the outer two juvenal
primary feathers, but had several juvenal primary coverts that were entirely
We banded just two Golden-winged
Warblers, both females, during spring.
Two more have been banded so far this summer, including our first male
(an SY) for 2002.
A Cerulean Warbler
banded on June 9 was too late to be included on our list of birds banded
this spring, and it was also a few days too late for visiting Cerulean
Warbler researcher (and former Louisiana Waterthrush
study field assistant), Kate Girvan, from Queen's University, and her field
For her doctoral research under Dr. Raleigh Robertson,
Kate has been mist-netting CERWs from throughout their breeding range (as
far south and west as Arkansas and east and north to Pennsylvania and southern
Ontario). She plans to analyze isotope ratios from samples of feathers
grown on the breeding grounds (i.e., retained juvenal feathers and/or feathers
replaced during the prebasic molt) and on the wintering grounds (i.e.,
body feathers and coverts replaced during the prealternate molt).
Kate hopes that isotope information obtained from carefully selected feathers
from CERWs caught at various locations throughout the species' breeding
range will provide insights into possible differences among breeding populations
in the location of their wintering grounds.
In the photo below of our recently banded
SY male CERW, the blacker, fresher inner greater coverts (replaced on the
bird's wintering grounds during its first prealternate molt) contrast with
the duller three outer greater coverts and carpal covert (molted last summer
during the first prebasic molt on or near the bird's natal grounds).
These first basic coverts, in turn, contrast with the retained juvenal
primary coverts and alula. Note, also, that there is the usual molt
limit seen in many passerines between the molted (first basic) alula
covert (blackish with a blue edge) and the two larger browner retained
juvenal middle and distal alula feathers. In the case of this bird,
the inner greater coverts, as well as any of the scattered darker median
and lesser coverts, from the alternate plumage would be expected to have
the isotope "signature" from its wintering grounds. The outer greater
coverts, as well as any of the scattered duller median and lesser coverts,
from the first basic plumage (also, any of the retained juvenal flight
feathers) would provide the breeding ground isotope signature.
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Answer: The juvenile
warbler pictured above is a Yellow Warbler