Pictorial_Highlights_091822

POWDERMILL NATURE RESERVE
PICTORIAL HIGHLIGHTS
September 18-22, 2002

Sunday, September 22, 2002

We've discussed and shown pictures at least twice before of adult female Hooded Warblers with unusually extensive, male-like black hoods. Just when we think we've seen the most extreme case (see Past PIctorial Highlights for July, where we showed a very masculine appearing female HOWA that had a brood patch) , another one comes along that seems to push the limits of this variation further still!

Even knowing that the bird pictured below was an adult (by its fully pneumatized skull and fully molted wing plumage), it still might have been mistaken for a male! Note, however, that the black throat and breast are not really contiguous and just a little less intensely black than would be expected in an adult (or even an immature) male. The bird's somewhat short wing length (i.e., compared to that expected for an adult male) of 64.0 mm also fit our determination that it was, in fact, a female. In the field, however, the bird surely would have been assumed to be a male!

While the adult female HOWA above clearly represents one end of the plumage gradient within that age-sex class, today we banded (in the same net round) two hatching year male Black-throated Blue Warblers that just about exemplified both extremes for plumage variation within that age-sex class. The top bird in the photos below has the most white in its throat that we've ever seen, in addition to having markings around its eyes not unlike a female BTBW; the lower bird, in contrast, has a solid black face with only a trace of white feathering in its upper chin (adult BTBWs have a solid black throat, including their chin).

Saturday, September 21, 2002:
Many migratory species exhibit a phenomenon called differential migration timing, wherein the age and/or sex classes within a species follow different schedules (e.g., on average, males may precede females; hatching year birds may precede adults). Our catch of many wood warblers today seemed to be comprised of a larger percentage of adults than observed earlier in the season. 44% of all warblers banded today were after hatching year (AHY) birds, and, within some species, this percentage was much higher--e.g., 55% of Magnolia Warblers, 75% of both Wilson's and Nashville warblers, and 83% of American Redstarts banded today were adults.

Below are photos taken of adults of three warbler species banded today--from top to bottom (two views of each species): Nashville Warbler (AHY male), Black-throated Green Warbler (AHY female), and American Redstart (AHY male).

In the NAWA, the very distinct gray head and upper back (and veiled dark chestnut cap) is characteristic of AHY males; adult female BTNW fall somewhere between very dull HY females and the more extensively and intensely black-throated HY males; AHY male AMREs, of course, are unmistakable!

Friday, September 20, 2002:
NOTE: As promised, we have posted additional photos and measurements (Click here) for the late Yellow Warbler (of unknown subspecies) banded yesterday and pictured and discussed in yesterday's notes (see below). If this information should lead someone to a more definitive opinion concerning which subspecies it might represent, we'd appreciate hearing about it!

We banded 56 wood warblers of 16 species, led by Magnolia (13) and Cape May (7). Among the wood warblers banded today was an exceptionally late migrant hatching year (HY) female Cerulean Warbler. In over 40 years of banding, we have caught only 13 CERWs in September, the latest before today being on 9/15. That this ordinarily is among our earlier migrants is further evidenced by the recovery of an immature CERW, originally banded here on 7/22/73, in Tortuguero National Park, Costa Rica on 9/12 of the same year.

Our second Bay-breasted Warbler of the season was this colorful (not too confusing!) fall adult (AHY) male.

In fall adult male Rose-breasted Grosbeaks molt from their boldly patterned solid black, white, and dark pink alternate (i.e., breeding) body plumage to a more subdued, but nonetheless still striking, basic (i.e., winter) plumage. In this plumage, their solid black head and back, bright pink chest, and clear white rump patch appear mottled by feathers that are edged and spotted with dark buff and black.

BandersBeware: they bite just as hard in either plumage!

Thursday, September 19, 2002:

Most unexpected catch of the day was the Yellow Warbler, pictured below. We last banded a YWAR this fall back on August 4. Yellow Warblers are very early fall migrants, and it is very unusual for us to catch any after the end of August. In fact, only seven YWARs have been banded later than 9/19 (the latest on 10/8). At least one of these very late YWARs was formally determined by Dr. Kenneth C. Parkes, Curator Emeritus of the Section of Birds of Carnegie Museum of Natural History, as belonging to the Alaskan subspecies, Dendroica petechia rubiginosa. We have suspected that other of our late banded YWARs also belonged to this or another northwestern race (e.g., D. p. amnicola) on account of their comparatively dark greenish dorsum and generally dull coloration. Today's YWAR, however, was not very dark greenish above and seemed unusual primarily in being very dully colored, with medium to light grayish green upperparts (especially the upper back) and with very pale whitish yellow underparts. Very conspicuous was a light, whitish gray area around its eyes, particularly in the lores, and a thin whitish eye ring.

This YWAR, which was a hatching year bird and a female based on dull color and short wing length (58.5 mm), may simply have been a very dull (and very late) migrant of the widespread eastern race, D. p. aestiva. Oddly enough, the bird bore some resemblance to plates in Dunn and Garrett's (1997) Peterson Field Guide to Warblers showing first year fall females of the Caribbean "Golden" Warbler race, D. p. petechia. We plan to put additional photos and measurements on a separate web page within a day or two for examination by anyone who may be interested. We certainly will appreciate hearing from anyone who feels that they may be able to lend some expertise to the subspecific determination of this bird.

An adult male Wilson's Warbler banded today was a particularly nice example, with a very extensive glossy black cap that measured 18 mm long (about the maximum).

A Brown Thrasher banded today was an adult (AHY) with its characteristic bright yellow-orange eye.

One of the Rose-breasted Grosbeak males banded today (top photo below) was a clear second year (SY) bird that had not yet molted four very brown and worn inner juvenal secondaries (retained from its hatching year, 2001). Only the outer primary and the adjacent, almost full grown secondary #2 were still slightly in sheath, and it seemed likely that this bird would shortly "arrest" its prebasic molt, completing it at a stopover site farther along its fall migration route, or perhaps not until reaching its wintering grounds. By comparison, the bottom photo below shows another adult male RBGR banded today that had already completed its definitive prebasic molt. This individual, of course, had to be aged simply AHY, because after a complete prebasic molt in the fall SY and ASYs can no longer be distinguished by plumage. Occasionally, however, ASY male RBGR can be distinguished if they, too, show an arrested molt pattern. In their case, any unmolted outer secondaries will be blackish rather than brown and much less worn than the retained juvenal flight feather of a SY bird with arrested molt/

Wednesday, September 18, 2002:

Although the many flight call notes heard this morning were dominated by thrushes of several species, it was quickly apparent from the banding that a wide variety of other species had moved into our banding area at dawn, including twenty species of wood warblers, two of these being new for the fall: Yellow-rumped (Myrtle) and "Western" Palm Warbler. Our overall catch of 45 species today represents excellent diversity for this station--only one day last fall, on 9/22, had a higher species count of 46. This is the third day this fall that we have banded >100 birds and our first day banding >200 birds.

The WPWA (top photo) and both MYWAs (one pictured in bottom photo) were particularly nondescript HY females.

Among the seven Cape May Warblers (which, incredibly, is our highest daily count since 1995 for this volatile--in a population dynamics sense--spruce budworm species) were two males, one each in the HY and AHY age classes. AHY male CMWAs (top photo) are almost as brightly colored in the fall as in the spring; HY males (bottom photo), much brighter than females of either age class, differ from adult males in being less bright yellow below, with a narrower upper white wing bar and no trace of chestnut in their cheek patch.

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