Winter 2005/2006 Notes and Highlights for December 07 - December 31

• The start of the winter season at Powdermill is somewhat arbitrarily defined as the beginning of December.  As most birders and banders know, however, migration seasons do not stop and start on a dime, and migration schedules can vary somewhat from year to year.  Because of the late and somewhat protracted fall flight of northern species like Dark-eyed Junco, Fox and White-throated Sparrow, and American Goldfinch, we decided to include the first week of December in our fall banding total this year.  In fact, a fairly heavy movement of new birds into the Powdermill banding station continued well into the second and even third weeks of December.  With many December banding days totaling between 40 and 60 new birds, a lot of the captures during the month may well be better classified as fall migrants, rather than local wintering birds.  In fact, in December we banded more than twice as many birds as we recaptured--the opposite trend is what we ordinarily observe during the winter.   As of this writing, two weeks into January, the large numbers of birds present almost daily at the feeding stations in the last half of December seem to have dispersed.

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• Whether we call it fall, winter, or both, an unusually big December catch rounded out a very busy 2005 banding year and gave us a year-end banding total of 13,458 birds, our fifth highest total ever (our record high annual total is 15,172, set in 1982).  The 447 birds banded in December (74 of which from the first week of December were included in the fall season totals) set a new record for the month (previous high was just 312 birds in December 1985).  Our total for all of last winter (Dec. 2004-Feb. 2005) was just 242 birds.  American Goldfinch (189) and Dark-eyed Junco (136) topped the December species list.  The Dark-eyed Junco numbers are particularly noteworthy, because this is the first time in recent years that DEJU numbers have returned to more historic levels.  In all, we banded 907 Dark-eyed Juncos in 2005, which is our highest annual total since 1996, when 1015 were banded.

• With 189 banded this month, we don't have a good excuse for not trying to make good on Dr. David Norman's strong suggestion, when he guest-authored our web page earlier this fall, for us do a special Powdermill banding website feature on variations in goldfinch molt.  We'll start with this installment on seasonal plumage variation and differences in molt in relation to ageing and sexing.

• Determining the sex of American Goldfinches in spring presents no challenge.  Even as early as March, many birds have begun their prealternate molt, which, in males, results in the unmistakable bright lemon yellow body plumage and black cap.  In basic (i.e. fall/winter) plumage, males and females more closely resemble each other, because males lose their black cap (usually, but not always!) and birds of all age and sex classes appear rather dull brownish yellow.

 

 

Ageing, for the most part, is no more of a challenge in one season than another, assuming, of course, that you know where and what to look for and how to interpret what you see.  The series of photos and discussion below should provide a general guide to making age determinations throughout the year and sex determinations in basic plumage (fall and winter).
 

• The first prebasic (fall) molt in goldfinches is not too variable.  It ordinarily includes most or all lesser and median coverts; very rarely a few inner greater coverts.  Importantly, the carpal covert, indicated by the red arrows in the photos below, is never included in this molt.  While age determinations should never be made based soley on one criterion, we have found the appearance of the carpal covert to be a reliable indicator of age, as hatch year (HY) birds' juvenal carpal covert almost always has a conspicuous buffy tip or terminal edge.  This can be seen very well on the wing in the photo below left.  The photo on the right, however, appropriately revisits the statement above, that it is unreliable to depend solely on one criterion.  Natural variation in the extent of feather color and variation in the wear of feather edging, in particular, can be misleading.  The wing on the right does belong to an HY male goldfinch.  While not as distinct as the wing on the left, there is faint buffy edging on the carpal covert.  What further supports this being an HY bird, though, is the shoulder (lesser coverts).  It is more yellow/green and brown and not completely lemon yellow as would typically be seen in adults (see photos below).

 

 
 
 

Notice that the body plumage is not necessarily distinctive between the female (bottom left) and male (bottom right).   While no female would have the black flecking seen in the forecrown on the male bird below, some adult females may have more yellow in the throat and around the head than is seen on the HY female bird below.  So, sexing goldfinches in basic plumage is done by assessing the blackness of the wing.  The wings of males of any age are jet black in color, while females are dusky (occasionally very dark dusky!) brown.

HY Female                                                                               HY Male

• The photos below are given for comparison to the HY birds above.  Both individuals are after hatch year (AHY) or adults; the male is on the top and left in the photos below and the female is on the bottom and right.  Notice the carpal covert of both wings completely lacks any buffy edging and the shoulder of the male, in particular, is much more completely yellow.  Without direct comparison, the darkness of the female's wing below may be misleading, but with one of each in hand, the sleek blackness of the male's wing becomes much more distinctive.

AHY Male
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AHY Female
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AHY Male                                                                         AHY Female

• Finally, the photo below, again, makes the point that natural variation in plumages can always be expected and must be acknowledged.  As many applicable criteria as possible should be evaluated (quickly and efficiently in order to minimize handling time for the bird) before arriving at a determination of the age of a goldfinch (or any bird, for that matter) in hand.

• Despite there being a distinct white (not buffy!) edge on the carpal covert, this is an AHY male goldfinch.  Alone, the carpal edging itself could easily be misleading, but the overall appearance of the wing leaves no room for doubt that the bird is an adult.  Again, the complete bright yellow shoulder should be helpful but, further, their is simply one generation of definitive adult feathers on the wing.  Were it an HY, we would see much more worn and brown flight feathers and primary coverts, in the least, contrasting with darker, fresher looking inner greater and/or median coverts.  While not illustrated here, tail shape can also be helpful in ageing goldfinches.  Adult's tails tend to be much broader as a whole and more round than pointy at the tips.

• In conclusion, the above criteria are meant as an aid to banders in making the correct age and sex determinations of individuals in the hand with 95% confidence.  We have handled known immature birds that had precociously developed bright yellow shoulders and known adult birds with unaccountably dull green shoulders and edged carpal coverts!  It goes without saying that more than a few goldfinches have been banded as unknown age (U in fall or AHY after Jan. 1) at Powdermill; we've even been stumped by the sex of a few!  But, after all, isn't all this variation (expected and unexpected) what makes bird banding (the entire natural world for that matter) so darn interesting and exciting?!   It's certainly what helps make the carefully recorded and reported observations of bird banders from throughout the world so scientifically valuable.

• postscript: Appropriately, it is also worth mentioning that in Europe, edging on the carpal covert is well documented as being age related for the Bullfinch Pyrrhula pyrrhula.  In Lars Svensson's Identification Guide to European Passerines....for 1Y (HY) - 2Y (SY) spring: coverts of alula and carpal ill-definedly tipped greyish brown...Ad: coverts of alula and carpal well definedly tipped and edged greyish white.  This is well illustrated both in Jenni and Winkler's Moult and Ageing of European Passerines (fig 610 and 611 on page 189) and on David Norman's Merseyside Ringing Group Website, click on 'bird in hand' and then 'end of winter 26 March 2005.'  As always, we appreciate David's across the seas connection.

• Four Brown-headed Cowbirds banded in December set a new month record for the species and were the first of their species to be banded in a winter since 1998.  The HY female pictured below was banded on 21 December and two other females and the HY male pictured below were caught on 27 December.

• All of the cowbirds were aged based on the retention of a few to many (as is the case in the photo below) retained juvenal underwing coverts.  Notice, also, there is a retained juvenal (light brown and worn) feather just above the shoulder of the male in the photo above.

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• This HY Swamp Sparrow, banded on 14 December, was noteworthy as the first winter SWSP in nine years.

• Also banded on the 14th was this HY male Red-bellied Woodpecker.  Woodpecker molt can be somewhat confusing beyond a bird's first year of life because up to three generations of feathers can be represented in the wing plumage.  One thing that is uniform in eastern North American woodpeckers is during the first prebasic molt all primaries (not the associated primary coverts), but no secondary flight feathers, are replaced.  This molt limit is clearly evident in the spread wing photo below.  Notice also that greater coverts 4 and 6-10 have been molted and contrast with the outermost retained brown juvenal GCs.

• Finally, we end this update with one of the last birds banded in 2005, this HY male Northern Flicker, banded on 31 December 2005.  Although the primaries vs. secondaries molt limit can't be seen well in this photo, the difference in brightness of the yellow feather shafts between the molted primaries and the duller retained juvenal primary coverts can.

• We thank Pam Ferkett, Dan Hinnebusch, and Cokie and Annie Lindsay for their help with banding this month.

Last Updated on 01//09/06
By Adrienne Leppold and Robert S. Mulvihill