- July 22-28, 2002: A highlight of the week was our banding of an adult and a juvenile (photo below) Eastern Screech Owl. Banding assistant Brian Jones, who spearheaded our owl banding efforts last fall, was the one responsible for successfully setting nets to catch some of the suspected EASO family group that had recently become very active (and vocal) in the banding area . Brian took both the EASO and the GCFL pictures below.
- Also noteworthy, especially considering that it was among our few "missed" species this spring, was our first Great Crested Flycatcher (an HY) of the year.
- We banded our first "fall" migrant Yellow-bellied Flycatcher, a female with a refeathering brood patch (photo below). Recall that not too long ago (June 15) we reported on banding our latest ever "spring" migrant of this species! Among the similar looking Empidonax flycatchers, the YBFL has the most prominent ruff of chin and throat feathers, something that (at least to our eye) gives it a "cuter" more round-headed appearance than other species in the genus with which it might be confused.
- Among the six Black-and-white Warblers banded this week, all but one of the following six possible age sex classes were represented: HY-F, HY-M, SY-F, SY-M, ASY-F, ASY-M. One adult (i.e., AHY) male had proceeded so far with its definitive prebasic molt that the alula feathers from the previous feather generation(s) necessary for distinguishing between SY and ASY were no longer present; the other "adult" male clearly was an SY bird based on molt limits.
The photo below shows the alula of the HY-M banded this week. In BAWW, as in many passerines, the juvenal middle and distal alula feathers are retained for a little more than a year, until the very last stages of the second prebasic molt (i.e., the molt that an SY bird is, or soon will be, undergoing). The small proximal feather of the alula, the so-called alula covert (visible at the top center of the photo) frequently is replaced during the first prebasic molt. Our good friend and very observant fellow bander, Jim Gruber, long ago pointed out to us that the juvenal middle alula feather in BAWW differs consistently in its pattern from the equivalent nonjuvenal feather. The juvenal BAWW middle alula always has just one or two white corner spots that do not meet at the tip of the feather, whereas the adult middle alula has a variable, but always continuous white terminal band. This is very helpful, because distinguishing between juvenal and the equivalent or adjacent adult feathers often is a matter of judging more subtle differences in color, lustre, shape, and wear. Unfortunately, we forgot to take a photo of the alula of one of the adult BAWWs this week for comparison, but we will do so at the earliest opportunity.
- HY male BAWWs (top photo below) lack the black cheek patch and black throat present to varying degrees in adult males in basic plumage, but they can nonetheless easily be distinguished from females (e.g., the HY-F in bottom photo below) by their more clean black-and-white appearance (i.e., they lack the buffy tinge present on the white head and side feathering of female BAWWs) and by the much more distinct streaking of their underparts.
- July 15-21, 2002: We banded our first HY Cedar Waxwings of the year on 7/21. Both were caught together in the same net and both had bright orange (instead of the normal yellow) tail bands--a consequence of their being fed large quantities of rhodoxanthin-containing Tartarian honeysuckle berries--suggesting that they may have fledged from the same nest. As the picture below shows, the width of the tail band differed markedly between the two birds. In CEDWs, males tend to have wider tail bands, on average, and it is likely that these unusually narrow and wide banded HY CEDWs were a female and male, respectively. Note, the pinkish cast to the belly feathers of the bird on the right is abnormal, being another manifestation of its honeysuckle diet.
- Over the years, we have observed an effect of abundant honeysuckle fruits in the vicinity of our net lanes on the plumage of several species of birds, including Yellow-breasted Chat, Kentucky Warbler, and Scarlet Tanager. One might question how we could discern this red berry's influence on the plumage of a normally bright reddish orange species like SCTA. The answer is that we sometimes see abnormal reddish orange coloration in HY birds, and we have even seen adult males in the midst of prebasic molt (which ordinarily would replace scarlet body feathers of the alternate plumage with yellow ones) growing scattered bright orange, rather than the expected yellow, basic body feathers. Finally, there are females (normally yellow in all plumages), like the adult caught this week, that are so unusually yellowish-orange colored that they might easily be mistaken at a glance for a Summer Tanager!
- Note, however, that a Summer Tanager would have a proportionately larger (especially longer) bill without such a prominent "tooth" on the upper mandible
- During the latter half of July, it is not unusual for us to capture the first individuals of species that nest, on average, considerably farther north or at higher elevations than our banding station. Oftentimes, these are hatching year birds. This week, for example, we banded our first Canada Warbler (an HY female) since May 26. Although we have banded more than 50 here in the month of July (>30 in July 1977 alone), it is always a surprise to take a Tennessee Warbler out of our nets at this time of year!
A very worn adult (ASY) male banded on 7/16 provided our second earliest "fall" capture of the species. It still had a prominent cloacal protuberance and had not yet begun its prebasic molt. All of the TEWAs banded at Powdermill in July have been adults (both females and males) showing signs of recent breeding condition (old, unrefeathered brood patches or cloacal protuberances), many of them in an early stage of prebasic molt. The nearest known nesting grounds for this species is about 500 miles north of Powdermill. We have always conjectured that these adults, which have already made a long distance movements away from their breeding grounds by the time they reach Powdermill, might represent failed or nonbreeders; alternatively, dispersal away from the breeding grounds before molting may possibly be characteristic life history strategy of some populations of the species.
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- Finally, although our photograph didn't turn out too well, we want to share this picture of a Hooded Warbler. It was undeniably an ASY female (still with a prominent brood patch) but with an unusually extensive (even for an adult female), male-like black hood and throat (compare to the photo of the immature male HOWA posted with last week's notes below).
- July 8-14, 2002: We banded a juvenile Eastern Bluebird this week whose photo can be added to the collection of spot-breasted immature thrushes from last week (see below).
- We still have not yet banded our first HY Cedar Waxwing of the year. Among the six adult CEDWs banded this week was the extra waxy ASY male pictured below. Ordinarily, In CEDWs red waxy appendages are restricted to the secondary flight feathers of the wing, giving a usual maximum of nine wax tips per wing (seven wax tips is by far the commonest number, however). Rarely, some tail feathers will also have the tips of their shafts red. More rarely still, small red wax tips can be seen on one to a few inner primary wing feathers. The extra waxy CEDW banded this week had large wax tips on all eighteen secondaries, all twelve rectrices and, in addition, small wax tips on the inner four primaries of each wing, for an impressive grand total of 38 waxy appendages!
- Thanks to differences in the timing of the first and definitive prebasic molts of young and adult passerines, respectively (add to that differences between those that have been receiving large amounts of parental care and those that have been providing it!), for awhile near the end of the breeding season, the difference between hatching year (HY) birds and after hatching year (AHY) birds of many species is almost as simple as the difference between birds that look fresh and whole (e.g., the HY male Hooded Warbler banded this week; top photo) and those that look bedraggled and piecemeal (e.g., yet another motley SY male American Redstart; bottom photo)! Can any parents out there relate?!
- July 1-7, 2002: Comparison of the loose-textured juvenal plumages of three species of thrushes banded this week (top to bottom: Wood Thrush, American Robin, Veery)
- Unlike the true thrushes above, most of which are not very far along at Powdermill in early July with the replacement of their fluffy juvenal body plumage and wing coverts (i.e., the first prebasic molt), many hatching year (HY) Louisiana Waterthrushes (among the very earliest nesting species at Powdermill, with most young fledging between late May and early June) have already finished their first prebasic molt and now show no traces of their downy juvenal body plumage and wing coverts.
At Powdermill, at least, non-molting LOWAs in fresh plumage in early July certainly are HY birds, because adult (AHY) LOWAs are all in some stage of wing and tail molt (which HY LOWAs do not undergo) at this time of year. Later in summer and fall, however (i.e., following completion of both the immature and adult prebasic molts), when both AHY and HY birds of many species are superficially very similar, banders will necessarily rely on a variety of techniques for separating the two age classes. These techniques vary in their ease of use and their reliability--unfortunately, many of the easier to use techniques, such as tail feather shape, can be misleading.
As an example, one of the HY LOWAs banded this week (photos below) had very broad retained juvenal rectrices (tail feathers) that could possibly have caused it to be mistaken for an AHY if a decision were made based on this criterion alone. The bird's retained (but still very fresh) juvenal tertials, however, did show the dark buffy or cinnamon colored edging characteristic (to one degree or another) of HY wood warblers in the genera Seiurus (to which the LOWA belongs), Oporornis (e.g., Kentucky Warbler), and Wilsonia (e.g., Canada Warbler).
Notwithstanding this, as a general rule, we have found that it is best to use less subtle and variable criteria than either feather edging color or tail feather shape for making age determinations. In species for which they are known to be useful, close examination of wing plumage for the presence or absence of molt limits and/or assessment of the degree of skull pneumatization, although more difficult techniques to employ, certainly are more reliable.
