Early morning mist nets shimmered in the warm sun this past week, and although banding conditions were not ideal with it reaching near 80 degrees on multiple days, diversity continued to rise as we netted 18 new species for the spring.  Our top species, once again, was Ruby-crowned Kinglet with 47 new birds being banded, all females (see discussion on differential migration of kinglets from Pictorial Highlights, April 20-25).

Blue Jay came in second with 32 banded and in the photo below, Valeria Ojeda (far right), learns about Blue Jay molt and compares the differences between an adult (ASY; bottom bird) and immature (SY; top bird) with Powdermill bander, Adrienne Leppold, and Powdermill volunteer, Randi Gerrish.  Valeria is an ornithologist from Argentina studying Magellanic Woodpecker breeding biology for her Ph.D., and she particulary enjoyed the summer-like weather that persisted much of the week during her visit, seeing as it is now becoming winter in her home in northwestern Patagonia.

Randi Gerrish, Carroll Labarthe, David Liebmann, Felicity Newell, and Valeria Ojeda all helped with banding this week.  Thank You!

• Tuesday, April 27:  We banded three of the 18 new species for this spring on the first day of the week, including this SY male Sharp-shinned Hawk in the first net round of the day (the other two new species banded this day were Swainson's Thrush and Kentucky Warbler).  Notice the pattern on the breast is streaked rather than horizontally barred as would be seen on an adult.  The yellow eye color is also an immature trait and will turn red as the bird ages.

• On Wednesday, April 28, we banded an adult male Blue-winged Warbler.  While not a new species for the spring, it nonetheless was interesting, because it had two broad yellowish wing bars, rather than the two well-separated whitish wing bars usually associated with the species.

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Blue-winged Warblers and Golden-winged Warblers commonly interbreed, with their distinctive hybrids known as "Brewster's" and "Lawrence's" Warblers.  There is considerable variation in the appearance of these hybrids, the genetics of which were established in a classic paper by Carnegie Museum's own Dr. Kenneth C. Parkes (1951. The genetics of the Golden-winged X Blue-winged Warbler complex. Wilson Bull. 63:5-15), retired Senior Curator of the Section of Birds.
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The yellowish wing-barred Blue-winged Warbler banded this week (top bird in photo below), while not an example of one of these named hybrids, represents what Dr. Parkes termed a crossover-type Blue-winged Warbler, a possible outcome of interbreeding between a Brewster's Warbler in which a crossover had occurred in the usually linked genes for wing bar and underparts coloration, and a "normal" Blue-winged Warbler.   For comparison, the bottom bird in the photo, also banded this week, is of a "pure" Blue-winged Warbler (note its clearer and distinctly separate bright white wing bars).

 

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• Thursday, April 29:  We banded 23 species of birds making it the most diverse day yet this spring.  Four were new and included Yellow-throated Vireo, American Redstart, this handsome SY male Prairie Warbler (notice the worn, brown retained juvenal distal alula),

and this irascible looking adult (ASY) White-eyed Vireo.  "What are you lookin' at?!"

• Saturday, May 1:  One of three new species banded today were two Orchard Orioles, an SY male and

an ASY female, caught together in the same net.

• Below is a picture of their spread wings:  immature (SY) male on the leftand adult (ASY) female on the right.  In this species, which exhibits delayed plumage maturation, the male's body plumage clearly distinguishes it as a second year bird.  Still, it is always useful (a good training exercise) for banders to take advantage of handling known SY birds to look for wing molt limits.  Especially in comparison with an adult, one can gain confident knowledge of molts and feather wear on SY birds and develop an eye for seeing such differences.  The SY male molted all its greater coverts and all three alula feathers.  He also molted secondaries 7-9 (tertials; not very clear in the photo) and his outermost four primaries, leaving a retained block of juvenal flight feathers in the middle of the wing (notice the shaft color difference between the outermost molted - black veined - and innermost retained - brown veined - primaries).  In addition, the appearance of the primary coverts in the SY male, in particular, are worn and very washed out compared to the ASY female.









• We netted a Gray Catbird that had a leg deformity we have never before seen.  Unlike avian pox, which was seemingly very prevalent this past fall, in particular, and which causes wart-like blistering growths on the feet and legs, this looked like incompletely shed tarsal sheaths on both legs.  Because this significantly increased the thickness of both tarsi, which likely would have been irritated by the attachment of a band, we released the bird unbanded.  Has anyone else observed this condition or know its pathological basis (e.g.,  fungal or bacterial infection)?

• Finally, on Sunday, May 2nd, we banded two more new species for the spring.  An "easy call" SY male Indigo Bunting,

• and what, after some deliberation, we finally decided was an oddly plumaged ASY male Magnolia Warbler.

• Magnolia Warblers can be surprisingly variable in appearance in spring, often because of differences in the extent of their prealternate molt (we have even caught MAWAs well into spring still cloaked entirely in very worn basic plumage!).  The bird above, however, clearly had undergone a fairly extensive prealternate molt, in the process acquiring a full black mask, solid black rump, and broad white inner greater coverts associated with the breeding plumage of male MAWAs.  Its back, however, was not the expected solid black, but instead had black-centered olive green feathering, like a female.  The lack of any molt limits ruled out its being a young (SY) male (an age/sex class that can closely resemble adult females, even in spring), and the bird's wing measured 62.0mm, which is within the range for males but outside that for females, based both on measurements of 100 males and females in Pyle (1997) and on >8,000 MAWA banding records summarized in our own recently published Relationships among body mass, fat, wing length, age, and sex for 170 species of birds banded at Powdermill Nature Reserve (Eastern Bird Banding Association Monograph No. 1), in which the mean adult female wing length is 57.6 mm (range 54-61.5mm), compared to 60.9 mm (55-63 mm) for adult males.  Our final determination for this bird, all things quickly but carefully considered, was, as we said, that it was an oddly plumaged ASY male.

Last Updated on 5/05/04
By Adrienne J. Leppold