Pictorial Highlights_ June

POWDERMILL NATURE RESERVE
PICTORIAL HIGHLIGHTS
June 2003

Wednesday-Sunday, June 25-29, 2003: A total of 110 birds of 27 species was banded over the course of five banding mornings this week, bringing our summer 2003 banding total to just under 400 birds of 49 species. Among six new species for the summer 2003 season banded this week was an immature Black-billed Cuckoo that was almost entirely in juvenal plumage (larger photo on left below). Seeing this juvenile reminded us of another BBCU that we banded two falls ago. That obviously very late hatched juvenile (smaller photo on right below, published previously on this website) was only a little farther along with its first prebasic molt on October 6, 2001 than the juvenile banded just a few days ago on June 27, 2003. You certainly wouldn't guess from their plumages that they were captured on dates more than 100 days apart!--especially when you see the very different looking Yellow Warblers pictured below, which were banded on the same day and probably hatched within a few weeks of one another.

The true juvenal plumage of many songbirds is ephemeral--the first prebasic molt often starts to replace juvenal body feathers and wing coverts within days after fledging, and frequently well before the juvenal wing and tail feathers have grown to full length. Immature birds wholly in juvenal plumage may, in fact, be limited to nestlings and not quite volant fledglings in many species. A few species, however, notably Song Sparrow, Swamp Sparrow, and Gray Catbird, may actually spend several weeks flying around in their juvenal plumage before the prebasic molt begins.

The renowned ornithologist and bird artist, Dr. George M. Sutton, was among the first to systematically describe and illustrate the often fleeting juvenal plumage of songbirds. Shortly after receiving his doctorate, and while still at Cornell University, he made a study of the plumages of eleven "sparrows" nesting at the Edwin S. George Wild-Life Reserve in southeastern Michigan. His study, from July 2 to August 16, 1934, resulted in the publication of Bulletin No. 3 of the Cranbrook Institute of Science, entitled "The juvenal plumage and postjuvenal molt in several species of Michigan sparrows." The work is illustrated with eight charming color plates of cute-looking stub-tailed cardinal, bunting, towhee, and several sparrows.

In contrast to the two BBCUs above that were caught with similar amounts of juvenal plumage remaining on widely different dates, this week we banded two immature Yellow Warblers on the same day that were outwardly in very different plumage: one (top photo below) was >90% in juvenal plumage, and the other (bottom photo below) had already replaced about 90% of the juvenal body plumage and wing coverts ordinarily replaced in this species during n the first prebasic molt. Given the fairly rapid rate at which the first prebasic molt proceeds, probably no more than a few weeks separate the hatching dates of these two birds. We very rarely catch YWARs in their full mouse gray and white juvenal plumage, when they surely would be "charming" to look at. Most (like the bird in the top photo below) are already molting in at least some scattered yellow feathers by the time they are flying around enough to be caught in our nets, and by this time "charming" and "cute-looking" aren't words that necessarily come to mind!

For banders, catching birds in summer in this active stage of plumage development provides a great opportunity for learning about molt limits (where they are and what they look like). In the top photo below, showing the actively molting wing of the younger juvenal YWAR pictured above, only the small lesser coverts (the epaulet or "shoulder" of the wing) are molting--the remainder of the wing and the adjacent body feathers obviously are juvenal, as evidenced by their duller coloration and looser texture. In the bottom photo below, which is of the older juvenal YWAR pictured above, all of the feather tracts of the wing that will be replaced during the first prebasic molt are molting or have molted. This includes the lesser coverts (as in the younger bird), the row of larger median coverts beneath them, the row of still larger greater coverts (and carpal covert) beneath the medians, and, lastly, the small alula covert (at the top right of the photo).

The difference in structure and appearance of the molted median and greater coverts, compared to the equivalent juvenal coverts in the younger bird, is striking. The difference in the older bird in the appearance and structure of the molted coverts and the unmolted but comparatively colorful and more tightly knit juvenal flight feathers, large alula feathers, and primary coverts, however, is not as obvious, and it is this more subtle difference, the so-called molt limit, that banders are looking for in order to age birds from fall through spring.

Now, the third picture that would be nice to have in this series would be of a hatching year YWAR that has finished growing its first basic lesser, median, greater, carpal, and alula coverts. We'll add that at the earliest opportunity! Until then, if you're a bander catching birds at this time of year and haven't done it before, start taking a good look at which feathers are molting in the juveniles you catch--remember, you're seeing molt limits in the making!

Wednesday-Sunday, June 18-22, 2003: The photo below shows an American Redstart ASY male with the characteristic bunched appearance of its inner primaries that signals that the onset of primary molt (i.e., the shedding of the first primary) is imminent. The next photos show an unusually brightly plumaged SY male Indigo Bunting, and a closeup of its wing plumage, which, like its body plumage, showed much more extensive prealternate molt than an SY male from last week (pictured below).

Friday-Sunday, June 13-15, 2003: 55 birds of 20 species were banded over the weekend, led by Cedar Waxwing (12 banded), Red-eyed Vireo (8) and Yellow Warbler (7). Like the American Redstart banded (and pictured) last week, individuals of other species banded this week had already begun their definitive prebasic molt, including a second year (SY) female Blue-gray Gnatcatcher (in a fairly advanced stage of molt, with a refeathering brood patch and molt score of 15 out of 90; photo below), and also a female Louisiana Waterthrush in an earlier stage of wing molt (molt score 4 out of a possible 90; not pictured). The waterthrush, which we determined to be a female by wing length and cloacal morphology, showed no sign of having developed a brood patch this season, presumably because all of her nesting attempts were lost well prior to completion of a full clutch of eggs (a brood patch ordinarily does not develop until a clutch is nearly completed). LOWAs usually are persistent renesters, with some experienced females observed to make as many as four attempts in a season, when the first three were lost at the egg or early nestling stage. The female banded this weekend, however, was an inexperienced, SY bird, who may have given up after just one or two unsuccessful attempts.

An SY male Black-and-white Warbler banded on Saturday also was in the early stages of molt, with its first three primaries recently dropped (molt score = 3; bottom photo below). Although this, its definitive (i.e., complete) prebasic molt, eventually will erase the molt limit created by its incomplete first prebasic molt last fall (note, especially, the contrast between the molted proximal alula, or alula covert, black with a continuous white terminal edge, at the top center of the picture and the retained brown juvenal middle alula with its characteristic discontinuous lateral white spots), it will be possible to recognize it as an SY until very near the end of the molt, when the alula finally is shed.

Especially because retained juvenal feathers become very worn through the summer, molt limits, like the conspicuously very brown middle and distal alula on the otherwise brightly plumaged male BAWW, can actually be observed by birders in the field (enterprising birders could even make a project of grouping their observations of selected species according to age and begin documenting, for example, possible age differences in spring migration timing, singing behavior, and nesting habitat).

We banded some other second year males that also would show obvious wing molt limits when observed in the field. Both the Rose-breasted Grosbeak and the Indigo Bunting pictured below, however, were in worn, even scraggly, breeding plumage, each showing much less than full replacement of their first basic (i.e., winter) body plumage, so that their identification as SY birds hardly would have required a close examination of their wing plumage! Still, they looked pretty good in comparison to the exceptionally dull SY male RBGR and INBU pictured here previously.

Note, again, that the very brown juvenal alula (in the BAWW pictured above) or primary coverts (in the case of the RBGR and INBU picture below) can form a conspicuous patch on the folded wings of SY birds, which could easily be spotted in the field and used to identify their age, even if their body plumage were more intact (compare with the first Scarlet Tanager example below).

In the wing plumage of the RBGR above (first photo below), the freshest feathers (from the prealternate molt) are greater covert 8, with the very large white spot, and secondaries 8 & 9. The lesser and median coverts probably were molted during the first stage of a protracted first prebasic molt that began on the breeding grounds last summer, with the somewhat blacker outer greater coverts, carpal covert, and alula being replaced during the remainder of this molt later in the fall or early winter. In the INBU wing (second photo below) no feathers appear to be very fresh, but the outer 4-5 median coverts are visibly fresher (i.e., blacker and bluer) than the even more worn inner median coverts and, therefore, must have been replaced during the prealternate molt. The rest of the wing coverts, the alula, inner secondaries 5-9 and outer primaries 4-9, were all replaced during the first prebasic molt last fall or early winter.

In contrast to the SY RBGR and INBU above, an SY male Scarlet Tanager banded on Sunday (first two photos below) was in high breeding plumage (almost equal to any ASY!), notwithstanding its still obvious wing molt limits. In addition to all of its body plumage, this bird's extensive first prealternate molt included a few lesser coverts, its median coverts, greater coverts 1-8, all three tertials, and all twelve rectrices (tail feathers); primary 1 was replaced adventitiously on the right wing only.

For comparison with the precocious SY male SCTA pictured above, we have reposted a picture of the less colorful SY male from last week, along with a spread wing photo of that bird showing its much less extensive prealternate molt (only greater covert 6, and possibly 10, and the tertials were replaced during its PA molt, with the rest of the wing being first basic or juvenal plumage). Again, in many species such molt limits can actually enable accurate ageing of birds even under field conditions (especially with the extraordinary optics, not to mention heightened birding skills, so widely available these days!)

Wednesday-Thursday, June 4-12, 2003: We apologize for the longer than usual time between website updates. The reason for this was a good one, however--we were very busy getting ready for and carrying out Powdermill's second annual BioForay from 6-11 June! On behalf of Powdermill, we would like to thank all the invited experts and enthusiastic naturalists whose participation and diligent work made this event so purposeful, educational, and enjoyable!

The cover collage below shows a selection of images (all by Mike Lanzone) taken during Powdermill's BioForay 2003.

This still new (and improving!) Powdermill and Carnegie Museum BioForay event is modelled after a great tradition of the Brooks Bird Club, which has conducted its annual "Forays" to observe, document, and monitor the diversity of birds, ferns, fungi, flowering plants, reptiles and amphibians, and more in natural areas throughout West Virginia since 1959.

Like our inaugural BioForay last year, Powdermill's second annual BioForay 2003 brought together Carnegie Museum, Powdermill, and other regional scientists having expertise with one or more taxonomic groups of flora or fauna, along with avocational naturalists interested in learning more about nature, for the purpose of documenting and scientifically monitoring biodiversity on large study plots (about 25 hectares, or 70 acres, each) at Powdermill Nature Reserve (eventually, throughout the Laurel Highlands ecoregion of southwestern Pennsylvania). Detailed data collected during BioForays include not just a list of species and forms, but also measures of abundance, and all data are geospatially referenced within each plot so that possibly important patterns of ecological co-occurrence can later be described and explored. Each plot (two in 2002 and one this year) is established as a permanent study site that can be revisted and re-examined at different seasons and in later years. Biodiversity studied in this way becomes much more than a static list of species and forms--it becomes a dynamic process driven by ecological interaction and environmental change.

Of special interest to visitors to this web page may be the results of our bird survey efforts during BioForay 2003. We conducted a total of 35 point counts at 14 sites with the study plot and later mapped the territories of all birds using standard spot-mapping methods. A total of 46 species were observed on the study plot, which is a young- to medium-aged second growth mixed deciduous forest that has both upland and riparian habitats and a small unreclamed strip mine (abandoned in 1947) at its center.

Based on our bird surveys and on exhaustive territory mapping, the most common bird on the 25-hectare plot was, not surprisingly, Red-eyed Vireo (23.5 territories). What was surprising (and encouraging) was that the second most common species (almost as common as the vireo) was Scarlet Tanager, with 19.5 territories! In the map shown below, the grids are 50x50 meters, and the small striped circles mark the locations of our primary point counts. CLICK HERE to see a complete list of birds found on the BioForay.

And, yes, before, during, and after the BioForay, we actually did manage to band some birds! For the first couple of days of banding after the close of the official spring banding season on 1 June, we were still catching migrants like Yellow-bellied Flycatcher (four banded), Northern Waterthrush, and Canada Warbler. Just four days after the close of the spring season, we caught our first Great Crested Flycatcher, which had been one of our spring 2003 "misses."

Toward the end of the current period, on June 11, we caught and banded a second year (SY) male American Redstart that had already begun its prebasic (i.e., post-breeding, or fall) wing molt (first three primaries of each wing missing or in full sheath)! Talk about a short summer!

<HOME>

Return to Past Pictorial Highlights