PICTORIAL HIGHLIGHTS, WEEK OF
Sunday, October 7, 2001:
Several of our banding interns and volunteers--Adrienne,
and Ben, spurred
on by Brian (photo
below)--put in an extra long day on Saturday, attempting to net for Northern
Saw-whet Owls last night. They were
successful at catching and banding one individual (our 103rd species for
the fall). Although technically banded yesterday (i.e., before midnight--see
clock in the photo) we have added it onto today's banding list.
Although this smallest of our eastern
North American owls can look rather cute to us,
it undoubtedly appears like the formidable
predator that it is
to the woodland mice, voles, and shrews
that must try
to avoid being caught in its sharp black talons!
Our fifth Orange-crowned
Warbler of the fall was our first that actually
had an orange crown (i.e., it was a hatching year, HY, male, while the
previous birds have been HY females). In this species, at least in
fresh basic (i.e., fall) plumage, the orange crown patch is entirely hidden,
so we had to continually part the bird's feathers for these photos (i.e.,
don't look for the crown patch to show in the field!)
Speaking of hidden crown patches,
the bright scarlet crown feathers of Ruby-crowned
Kinglet males (present in the basic, i.e.,
fall, and alternate, i.e., spring, plumages of both hatching year, HY,
and after hatching year, AHY, birds) are visible only when a bird chooses
to display them, such as when it is involved in an agonistic encounter,
or when a photographer parts them (photo below, left).
Very rarely (~5 in 1,000, based on ca. 4,000
Powdermill fall banding records) female RCKIs
may have a few red or orange crown feathers. Today we banded an adult
female with a small red crown patch, comprised of no more than a half dozen
feathers (photo below, right). We judged this bird to be a female
(as opposed to a male with an abnormally small red crown) because it was
an AHY with a very short wing of just 53.5mm (males typically have wing
lengths >58mm). Unlike the bilateral
(see notes below from October 4), whose sexually ambiguous plumage
has an underlying genetic basis, the occurrence in a very small percentage
of RCKI females
of the males' secondary sexual plumage trait, a red crown (albeit reduced
in extent), could be due to injury or atrophy of the ovaries or may possibly
have a senescent basis (i.e., resulting from changing levels of circulating
hormones with advancing age).
Saturday, October 6, 2001:
Most unusual bird banded today was a late, and
still very immature (i.e., late-hatched), Black-billed
Cuckoo. The picture below shows the
bird, an unusually small individual (wing chord, 126.5mm; body mass, 43.6g),
with extensive retained juvenal plumage (both body feathers and wing coverts,
with light buffy edges).
During October it seems like most of the birds
we catch are one shade of brown or another, so this brightly colored adult
male Golden-crowned Kinglet
(top) and Purple Finch (bottom)
caught our eye for today's photo highlights.
Thursday, October 4, 2001:
Calm, clear, moonlit, and mild early AM; becoming sunny, warm, and windy
by noon (nets closed at noon).
said goodbye early this morning (before net opening) to our good helper
and office mate for the last seven weeks, Fränzi
Nievergelt, a visiting doctoral student and
ringer (European for "bird bander") from Switzerland.
We are very glad that Fränzi
found our website and made arrangements to come to Powdermill to conduct
some of her research here this fall--not only was she wonderful company
in the office, but also without her help we could not have banded as many
birds. We wish her all the best with her academic studies and her
doctoral research back home in Zurich.
It was a "red-letter"
day for banding at Powdermill, not because of how many birds we banded
(only 64), but because of how interesting some of the birds were that we
banded (yes, thank goodness, the digital camera is fixed!). But,
before we get to the digital photo highlights, here are a couple digital
recordings of one of our "red-letter" birds--see if you can guess who this
angry growler is:
Now, click here
to see pictures of the bird.
The second "red-letter"
bird of the day is best classified as a biological oddity (banders just
never know what's going to fly into their nets next!)--no, not a two-headed
Towhee, but a two-sided one! The technical
term is bilateral gynandromorph.
extremely rare genetic variants in vertebrates, express both male and female
morphological traits (both plumage and size), roughly along the central
body axis. The immature towhee that we banded today was mostly
female in appearance on the right side and mostly male on the left side
(although male plumage intermixed with female feathers to some degree on
the right side of the head). The bird's rectrices (tail feathers)
were intermixed brown and black, although not strictly divided along the
central body axis. We have observed two other bilateral gynandromorphs
at Powdermill in 40 years--a Northern Cardinal
and an Evening Grosbeak.
In line with its plumage differences, the gynandromorph
towhee's right wing length (the smaller, female side) was 83.0mm, compared
to 85.0mm for its left wing; there were similar differences for tarsus
(27.0mm vs. 29.0mm) and hind toe without claw (10.0mm vs. 11.5mm).
Also interesting was the asymmetry in extent
of first prebasic (i.e., post-juvenal) molt between the towhee's wings.
Among passerines, males often molt more extensively than females, and this
bird was no exception--molt on the male side of this bird included secondaries
6-9, while on the right side only secondaries 8 & 9 were molted (molt
limits visible in the photo below). In the photo below, note also
differences in color of the molted secondaries and secondary coverts between
wings (left side black, right side brown).
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