Pictorial_Highlights_100207

PICTORIAL HIGHLIGHTS, WEEK OF 10/02/01-10/07/01

Sunday, October 7, 2001:

Several of our banding interns and volunteers--Adrienne, Annie, 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 gynandromorph towhee (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).

We 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:

recording 1

recording 2

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 Eastern Towhee, but a two-sided one! The technical term is bilateral gynandromorph.

Bilateral gynandromorphs, 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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