Pictorial_Highlights_101621

PICTORIAL HIGHLIGHTS, WEEK OF 10/16/01-10/21/01

Sunday, October 21, 2001:

The three banded today brought our Winter Wren fall total to 48, which exceeds our previous record fall total for this species established just last fall.

Here's no. 48 in a classic, tail-up, wren pose!

Saturday, October 20, 2001:

Banding highlights included another Orange-crowned Warbler and Red-breasted Nuthatch, as well as another late Magnolia Warbler. Eclipsing all of these highlights, however, was the first "Gambel's" White-crowned Sparrow ever banded at Powdermill. This northwestern subspecies of the WCSP breeds from Alaska and British Columbia to the Northwest Territories and northern Manitoba. The bird caught at Powdermill, a hatching year (HY) bird, was distinguishable from the usual eastern race by its light-colored lores (i.e., the light-colored supercilium extends over the bill) and its yellowish orange, rather than pinkish, bill.

Friday, October 19, 2001:

We had several banding highlights, including three Orange-crowned Warblers in one net round (bringing our fall total for this rare species to ten), two more Pine Siskins, and one new species for the fall--an adult Henslow's Sparrow. Although we also banded a HESP last fall, lack of suitable habitat in the banding area makes this species a very rare (only 11 have been banded here in 40 years) and always exciting catch for us.

Because HESPs are difficult to see well in the field, it is especially nice to be able to examine the colorful and intricate plumage of this species in the hand--the detail below is of the bird's nape and upper back feathering.

Thursday, October 18, 2001:

White-throated Sparrow is another species, like the Purple Finch discussed and pictured in yesterday's notes, having a very variable plumage--in this case, literally a plumage polymorphism. In WTSP, a specific chromosomal polymorphism gives rise to the so-called "bright" or "white stripe" and "dull" or "tan stripe" morphs, and these morphs, or plumage variants, can occur in both male and female and immature and adult birds. Although the genetics of this polymorphism suggest that all WTSP can be categorized phenotypically (i.e., in terms of the outward, morphological expression of their genetic make-up) as either "dull" or "bright," there is, in fact, considerable variation within each of these categories (i.e., the brightest individual among those having the "dull" chromosome variation may approach in appearance the dullest bird having the chromosome type associated with "bright" coloration). In WTSPs, the phenotypic differences between birds with the different chromosome types are most pronounced in alternate (i.e., nuptial, or breeding) plumage.

Today, however, we caught two birds (photo below) in basic (i.e., non-breeding, or winter) plumage that illustrate very well the extremes of the plumage polymorphism in WTSP. In this example it happens that the "bright" morph bird on the right was an adult (and probably a male based on wing length) and the "dull" morph individual on the left was an immature (and probably a female), but it is possible to find examples of the reverse case (i.e., "dull" adult males and "bright" immature females). The degree of the phenotypic differences between the morphs in fall, however, generally would not be as extreme in the reverse case.

The key phenotypic differences between the WTSP morphs are:

Bright Morph	Dull Morph
bright white median crown stripe	tan median crown stripe
black lateral crown stripes	mixed brown/black lateral crown stripes
bright yellow lores	dull yellow lores
gray, unstreaked breast	whitish, streaked breast
bright white throat patch without black malar streaks	dull white throat patch with distinct malar streaks

Wednesday, October 17, 2001:

We have already posted several pictures of Purple Finches this season, mostly adult males and molting birds. The plumage of adult females (and also immature males) is highly variable, often being more or less plain olive brown (top photo), but sometimes having a conspicuous tinge of greenish yellow, gold, orange, or even "purple" (bottom photo), especially on the rump, lower back, and greater wing coverts (and sometimes on the chin and throat).

Tuesday, October 16, 2001:

For the record, the busiest day ever at Powdermill was on 10/16/65, when 621 birds were banded (110 of which were Field Sparrows). FISPs would not have made up the bulk of a full catch today--we only banded three (they didn't even make the top five). This species is one of very few that has decreased in abundance over the program's 40-year history, undoubtedly due to habitat loss resulting from natural succession of the early old field habitats (once much more extensive at Powdermill) that they prefer.

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