• June 24-30, 2002:  

 
• Four of the six OVENs were banded today on 6/30--three out of these four showed no signs yet of beginning prebasic molt and one was in the very earliest stage, having just recently dropped its first and second primaries.  As we have mentioned here before, it is very common for some kinds of forest nesting songbirds at Powdermill to leave their woodland breeding habitats shortly after completion of nesting (often in the company of  their fledglings) and move into the dense riparian and upland shrub- scrub habitats where our nets are located.  These more densely vegtated habitats not only provide additional cover and food for the inexperienced fledglings, but also a protected place for adults to undergo their annual wing molt, which, at its height, can reduce their flight ability and, consequently, their ability to escape predators.

• In order to study wing molt in a quantitative way, banders often assign a numerical rank (0-5) to each flight feather.  An unmolted feather receives a score of "0;" a feather just dropped or in "pin" scores a "1;"  in the "brush" stage up to 1/3 grown rates a "2;"  from 1/3 to 2/3 grown is a "3;"  from 2/3 to almost fully grown is a "4;" freshly molted and fully grown scores "5."  Prior to the onset of molt, birds have a total molt score of zero.   At  molt completion (all feathers scoring a "5"), for birds with nine primaries and nine secondaries, the total molt score is 90.  By scoring molt in this way, the timing and rate of molt within and between species can be easily compared.


Many species at Powdermill, including most American Redstarts, are well along with their molt now.  The photos below show two different second year (SY) male American Redstarts caught on 6/30 that were molting from their female-like gray and yellow plumage to their definitive black and orange.  The top bird's molt score was 12, while the bottom bird scored a 24.

• By way of comparison, the molting Yellow Warbler pictured below had a molt score of 20--a total of nine feathers, the inner six primaries and the inner three secondaries (also called the tertials) were actively molting.  This molt sequence--inner primaries first (beginning with primary 1 and proceeding outward) , followed by the tertials (inner secondaries 7-9; usually sec. 8 first, followed by 7 & 9) and, lastly, by the outer secondaries (beginning with secondary 1 and progressing inward toward the tertials)--is the characteristic molt sequence of most adult passerines.

• At the same time that we are catching many motley (i.e., molty) adults (some of which, like the SY-M AMRE below, are hardly even recognizable!),

 
we are also catching juveniles of many local breeding species.  When these are still clad mostly in their fluffy juvenal plumage, they can be puzzling as well!  Thankfully, most species begin molting out of this often nondescript plumage within days after fledging.  Do you know the species of warbler pictured below?  (Answer at the bottom of this page)

• June 3-23, 2002:   
  
  
• During the period, we banded an SY male Scarlet Tanager that had an unusual plumage.   To begin with, its prealternate body molt evidently was not complete--the bird still had a considerable number of  retained (and worn) yellow-olive basic body feathers.  Even those body feathers that had been replaced during the prealternate molt were orange rather than the usual scarlet red.

• But even more unusual were the bird's scattered white or partly white wing feathers.  All three outer juvenal primaries on the right wing, as well as one juvenal primary covert, were entirely white.   They were noticeably much more worn than the neighboring wing feathers.  This is because they lacked the melanin pigments that strengthen feathers and make them more resistant to abrasion.  In the closeup lower photo, compare the degree of wear between the tips of the white juvenal outer primaries 7-9, the normally pigmented (much fresher and probably adventitiously replaced) primary no. 6, and even compared to retained juvenal primary no. 5.   The bird's left wing showed only slight loss of pigmentation at the very tips of the outer two juvenal primary feathers, but had several juvenal primary coverts that were entirely white.

• We banded just two Golden-winged Warblers, both females, during spring.  Two more have been banded so far this summer, including our first male (an SY) for 2002.

• A Cerulean Warbler banded on June 9 was too late to be included on our list of birds banded this spring, and it was also a few days too late for visiting Cerulean Warbler researcher (and former Louisiana Waterthrush study field assistant), Kate Girvan, from Queen's University, and her field assistant Chris.

For her doctoral research under Dr. Raleigh Robertson, Kate has been mist-netting CERWs from throughout their breeding range (as far south and west as Arkansas and east and north to Pennsylvania and southern Ontario).  She plans to analyze isotope ratios from samples of feathers grown on the breeding grounds (i.e., retained juvenal feathers and/or feathers replaced during the prebasic molt) and on the wintering grounds (i.e., body feathers and coverts replaced during the prealternate molt).   Kate hopes that isotope information obtained from carefully selected feathers from CERWs caught at various locations throughout the species' breeding range will provide insights into possible differences among breeding populations in the location of their wintering grounds.

In the photo below of our recently banded SY male CERW, the blacker, fresher inner greater coverts (replaced on the bird's wintering grounds during its first prealternate molt) contrast with the duller three outer greater coverts and carpal covert (molted last summer during the first prebasic molt on or near the bird's natal grounds).  These first basic coverts, in turn, contrast with the retained juvenal primary coverts and alula.  Note, also, that there is the usual molt limit seen in many passerines between the molted (first basic)  alula covert (blackish with a blue edge) and the two larger browner retained juvenal middle and distal alula feathers.  In the case of this bird, the inner greater coverts, as well as any of the scattered darker median and lesser coverts, from the alternate plumage would be expected to have the isotope "signature" from its wintering grounds.  The outer greater coverts, as well as any of the scattered duller median and lesser coverts, from the first basic plumage (also, any of the retained juvenal flight feathers) would provide the breeding ground isotope signature.

Answer:  The juvenile warbler pictured above is a Yellow Warbler