This week marked the end of the Spring 2004 banding season here at Powdermill.  135 birds were banded, and, like last week, two new species were added to our season list, bringing our total to 99 species of birds  banded this spring.  Cedar Waxwing was again the top species for the week, with 28 banded.  Weather was drier than last week, with no real threat of rain affecting banding effort, but temperatures continued to reach into the high 70's and 80's, shortening our banding days somewhat.

We had help this week from Randi Gerrish, Dan Hinnebusch, Melissa Jakubcak, Mike Lohr, Felicity Newell, Janice Sweet, and Sandra Terwilliger.  Thank You!!

• The transition into the summer season through our last week of "spring" was heralded by our capture of the first locally hatched birds for 2004.  We banded three fledgling Song Sparrows this week.  The first two (one of these pictured below) were caught in successive rounds in the same net near the banding lab on Friday, May 28th and likely were siblings.   They, and a third juvenile SOSP banded later in the week, were aged local (L), as opposed to hatching-year (HY), because their juvenal plumage was not yet fully developed, they were incapable of strong, sustained flight, and they were still being cared for by adults (as evidenced by the protests while the young were being extracted from the nets!)

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At Powdermill, we always give banding priority to dependent young like this and/or to adults (especially females) that may be caring for young or incubating eggs.  Not only do we band and process these birds first upon returning to the banding lab from making our net rounds, we return them to the site of capture as soon after processing as possible.  In the case of recaptured banded females with edematous brood patches (see below), especially in very cool or very warm weather, we often record the band number and the bird's age and sex after extracting it from the net and simply release it on the spot.

• This time of year (namely, the breeding season) is particularly advantageous for banders because sex-specific physiological changes in many species can allow otherwise unknown sex birds to be designated as either male or female.  As most birders and banders know, there are many sexually dimorphic species (i.e. birds that can be sexed based on external characteristics, such as plumage coloration and/or size).  Sexually monomorphic species (i.e., birds in which females and males look exactly or very nearly alike), however, can only be sexed in the hand in spring and summer, and only if they show a cloacal protuberance (C.P.) or brood patch (B.P.).

In many monomorphic species, the male's cloaca becomes enlarged and bulbous during the breeding season, enabling more effective contact with the female's cloaca during copulation.  This is called a cloacal protuberance, or C.P.  During the developing stages, the swelling of a male's cloaca will not be as obvious in the hand as the one in the photo below (we barely even had to part this SWSP feathers to see its C.P.), but nonetheless can be identified by an experienced eye.

Females will lose the feathers on the belly area in order to have direct skin contact and maximum heat transfer to the eggs in the nest.  The photo on the right shows a highly developed B.P. with wrinkly and vascularized skin.  Similar to the development of the males' C.P., a female's B.P. will progress in stages, from shedding the feathers of the belly to the blood vessels increasing in size and number under the skin, until the patch is edematous (i.e. highly vascularized and swollen).  The photos below are of a male Swamp Sparrow (left) and female Gray Catbird (right) in breeding condition.

• We have previously posted pictures of Scarlet Tanagers on the website this spring but just couldn't pass up the opportunity to share a couple more pictures of these strikingly spectacular birds.  The top photo was one of the most brilliant adult males we have seen in a while.  Contrastingly, the bottom photo is of the head of a second year (SY) male that had an incomplete prealternate body molt, retaining scattered first basic head feathers (shown in the picture) and also yellowish first basic feathers along his flanks (compare with the photos from the more typically plumaged immature SCTA posted a couple weeks ago in Past Pictorial Highlights - May 11th).

 

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• The first of our last two new species for the spring was netted on Wednesday, May 26--an after hatch year (AHY) female Eastern Kingbird with a brood patch.  We regularly capture fewer than one of this species a year, and last year was one of twelve out of the past 43 years in which we "missed" banding EAKI, so we were excited to see her in our nets.  We promptly banded and processed her, took a few seconds for some quick photos (the bottom one with parted head feathers to show the very well concealed yellow/orange crown patch), and then quickly released her so she could return to her nest.

• Our second new species was captured three days later on Saturday, May 29, this immature (second year, SY) Great Crested Flycatcher of unknown sex.  This, like the kingbird, is a species we catch very few of each year so we were glad to add it to our species list for the spring.  Immature birds of this species may have had a fairly extensive replacement of juvenal feathers by this time of year, having undergone both prebasic and prealternate molts, therefore making ageing difficult.  This particular individual, however, molted its entire tail except for its, now very worn, brown, narrow and tapered juvenal rectrix 5, the second feather in from the right (R3 on the right is missing), clearly telling us it was an SY bird.  We noticed that the centrral two pairs of rectrices appeared fresher than the outer rectrices, in which case this bird had three feather generations making up its tail plumage:  juvenal, first basic, and first alternate.  The molts of many of the tyrannid flycatchers are complicated and more data are needed before we can fully describe the variation in their molt strategies within and across species

 

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• Sunday, May 30th, our last day of banding for the spring season provided us with a few final interesting opportunities for photos and discussion of the birds at Powdermill.  This immature (second year, SY) female Magnolia Warbler was a case of a very limited prealternate molt with extreme feather wear.  This bird was basically still in first basic plumage except for the four molted (black-centered) feathers on her back.

• Her only other freshly molted feathers were seven adventitiously replaced (i.e., after accidental loss) rectrices.  Note the marked difference in the appearance (color, shape, and wear) of the adult-like replacement tail feathers.

• Lastly, we banded this unusual, multi-colored adult (ASY) male Cedar Waxwing.  At Powdermill, we rarely catch adults with orange tail bands because the timing of their molt is past the period when Morrow's and Tartarian honeysuckle berries are fruiting (click here to read about the rhodoxanthin pigment in the berries that causes the variant orange feather color).  This was a unique bird because, not only did all but the central two pairs of rectrices have well developed orange tips (top photo), but there was also a hint of orange coloring on his flanks (bottom photo).

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Occasionally, we have caught adult waxwings that have a few orange-tipped rects which have been replaced mid-summer (late June-July) when ripe honeysuckle fruits are abundant at Powdermill.  This bird was unusual because it evidently molted in his orange tail band during normal prebasic molt last fall.  The slightly fresher, yellow-tipped central rectrices are replacement feathers grown relatively soon after the fall molt (as evidenced by the similar degree of wear).  While almost all of our orange tail variants are juveniles, again, because the molt of adult CEDWs at Powdermill does not coincide with the fruiting of the honeysuckles, studies by Mark Witmer ("Consequences of an alien shrub on the plumage coloration and ecology of Cedar Waxwings." 1996. The Auk. 113:735-743) of waxwings near Ithaca New York show that more protracted availability of ripe honeysuckle berries there does overlap with the timing of adult CEDW prebasic molt.  He also found that adult CEDWs from that region frequently had orange tail bands.  Presumably, the CEDW pictured below was from somewhere in the breeding range where the fruiting season for these honeysuckles is extended.

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• We have again included a mini photo gallery for the rest of our birds that provided great and interesting photo ops at Powdermill Nature Reserve this week.  Note:  You will have to use your browser back button to return

to this page from the links below.

• Rose-breasted Grosbeak (ASY/M)
• Gray-cheeked Thrush (ASY/U)
• American Goldfinch (ASY/F)

Last Updated on 6/2/04
By Adrienne J. Leppold