Summer 2006 Notes and Highlights for the month of June

• June typically marks the transition into the summer season here at Powdermill.  While spring migration might linger on in some years with a few late migrants banded into the first week of June, this year was certainly not the case.  Some of the birds, American Redstarts in particular, were even already showing signs (onset of prebasic molt) this month that their nesting season is over for this year.  Blink and you really could miss the nesting season for many species--in fact, it is only a matter of time (perhaps a month or less) before we'll detect southward (fall) migratory movements of some individuals and species.

• Because there is less activity in the summer months, and also to minimize interruptions to breeding adults and their nestlings/fledglings, the Powdermill banding operation is scaled back during June and July.  We band only four days a week with a maximum of only 30 nets run on any given day (migration banding takes place six days a week with 60 or more nets operated each day, weather permitting).  Thus far, we have banded 364 birds of 49 species.  American Goldfinch topped June totals with 63 banded followed by Cedar Waxwing (47), Gray Catbird (36), Red-eyed Vireo (30), and American Redstart (22).  We thank Brent Worls, Jessica Scopel, Lauren Schneider, Jake and Courtney Hughes, Luke Pajer, Pam Ferkett, Christian Meny, and Jerry Simmons for their help this month with banding.

• Ironically, the first pictorial highlight for June was our one and only indubitable late spring migrant.  Banded on June 11th and tying for the latest recorded date of this bird at Powdermill, it was an immature (SY) Wilson's Warbler in incredibly worn 1st basic plumage; the bottom photo below shows the extreme wear on her wings and tail, perhaps something that contributed to her very late arrival at Powdermill.  This bird had very little fat and weighed just 7.7 grams when she was banded.   There are certainly no breeding accounts in Pennsylvania for WIWAs, and the nearest known breeding grounds for the species are the Adirondack Mountains in northern New York, where a very small disjunct population exists, and northern New England.

There have been sixteen other June captures of WIWA at Powdermill, about evenly split between males and females.  More than half of these had heavy fat deposits when they were banded, and two SY males banded in the first week of June were recorded as having partially developed cloacal protuberances.   It would be interesting to know if late birds like these (and especially very late ones like this June's individual) are, in fact, capable of continuing on successfully to their breeding grounds, or if they might need to stop short somewhere.  If the latter, then how would the failure to attain full physiological breeding condition affect the onset and timing of their "post-breeding" molt?  Presumably, and as we often witness with resident breeding birds at Powdermill (see AMRE discussion below), they initiate this molt much earlier than other breeding individuals of the population.

• As we've mentioned on the website frequently in the past, SY male American Redstarts are notably less successful at acquiring mates and territories during the breeding season and begin their annual prebasic (post-breeding) molt as early as early to mid-June.  The bird in the photo below is farther along in its molt because the picture was actually taken the first week of July, but given the extent of molt, it actually commenced a week or two ago in June.

• Another reason that we may see birds molting as early as mid-June is because they are an earlier arriving species that have already successfully completed nesting and raising young.  We have been studying Louisiana Waterthrushes at Powdermill as bioindicators of stream quality in the region now for 11 years, and we know the phenology of their breeding season very well.  They are certainly the earliest arriving neotropical migrant wood warbler with males establishing territories as early as late March.  In first nests, clutches usually are completed before the end of April.  In these cases, young would typically be fledged by the middle to the end of May.  In which case, adults begin molting in mid-June (not infrequently overlapping this with the last stages of post-flegding care) and begin actively migrating before the end of July.  This adult male LOWA, banded on June 16, was poised to do just that being well underway with his prebasic molt.

• Finally, we see many birds at Powdermill that have reached their breeding grounds here, show signs they have at least attempted to nest, but which apparently have had their breeding season cut short by failure, making yet another reason for the early onset of post-breeding molt.  This could have possibly been the case with the Black-and-white Warbler banded on 25 June.  She had already dropped her first three primaries and five greater coverts (P1, just breaking sheath, is slightly visible underneath the outermost greater coverts) and also showed physical evidence (an old unfeathered brood patch) that she had at least attempted to nest.  The comparatively advanced stage of molt for this female BAWW on this date suggests the possibility that her nesting attempt failed and that, for reasons we could only guess, she did not make a renesting attempt.

Postscript:  After reviewing data regarding the extent and timing of molt taken from birds at Powdermill over the last 10+ years, this is actually one of the earliest dates recorded for the onset of molt in BAWW.  The average onset of molt witnessed for this species at Powdermill is about the second week of July.  Thanks to Dr. David Norman for his work in summarizing this information (timing of onset and rate of the definitive prebasic molt of birds banded at Powdermill), which he and Bob Mulvihill will publish as part of an upcoming molt monograph.

• Some highlights of true products of the breeding season include a hatch year (HY) male (with the red juvenal crown) Hairy Woodpecker (top photo), a juvenile Red-winged Blackbird (middle photo), and an HY Rose-breasted Grosbeak male (bottom photos) just molting in its rose underwings.

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• Because there is less banding activity during the summer months, as mentioned above in the introduction, Powdermill Avian Research Center staff were able to lend a helping hand to a very different banding research project in the eastern portion of  the state, and also one right here at Powdermill.  First, we traveled to Harrisburg to assist Dr. Terry Master and two of his graduate students from East Stroudsberg University in marking chicks at a large nesting colony of Great Egrets and Black-crowned Night Herons (both endangered in the state of Pennsylvania).  Wade Island, in the Susqehanna River near Harrisburg, is home to PA's stronghold of these threatened breeding birds.  This particular study aims to learn more about adult foraging movements and dispersal, assess the competition from the newly arrived Double-crested Cormorants to the island, and hopefully, in subsequent years of the study, begin to analyze productivity, survivorship, and recruitment rates for this population.  In order to gain information about the latter three variables, Dr. Master has embarked on an effort to band chicks (and eventually affix some with radio transmitters), and this is where the Powdermill team stepped in to help.

• Once at the island, we were joined by Terry's two grad students working on this project, Brad Romano          and Don Detweiler.  In the photo below, Brad, on the ladder steadied by Don, is retrieving juvenile Black-crowned Night Herons from the nest for banding as Sara and Terry (off to the right) are prepared for any out chicks of Brad's reach that may jump from the tree.  The whitish film over all of the broad leaves in the trees and on the ground in the photo below is heron guano (i.e., dried excrement), which gave the island the distinct (and strong!) odor of fertilizer.

• We successfully captured and marked 13 juvenile Black-crowned Night Herons, which we all felt was a productive effort for our pilot attempts.  The top photo below is a close up of one of the 13 banded and in the bottom photo below, Bob Mulvihill measures the wing of a recently banded young.  Birds were also marked with a color band, in addition to the standard USGS aluminum band, for easy resighting of individulas in future seasons.  In the background of the bottom photo, Mike Lanzone tests out telemetry receivers that will be attached to birds caught during subsequent visits to the island in an effort to track the post breeding and foraging dispersal of birds from this colony.

• Following processing, all the chicks were promptly taken back to their nest sites and placed right back in the trees where they were found.  Below, Sara Nicholas pauses for a moment for a quick photo with one of the BCNH chicks before returning it to its nest.  On behalf of Terry and his ESU grad students, we thank the WRCP for its significant contribution to funding this important research project and Sara for providing a literal helping hand on top of that.

• Just shortly after returning from heron banding in Harrisburg, we welcomed Melissa Duron (right in the photo below), research biologist, and Maria Neal (on the left), research assistant, working under Dr. David Evers at the Biodiversity Research Institute in Gorham, ME.  Their visit to Powdermill was one of many scheduled stops in various locations around PA and NY collecting samples from forest songbirds to test for the presence of and levels of methylmercury (MeHg).  We were more than happy to be a collaborator in this important research project.

 

 
 
 
 
 

Recent studies have shown negative impacts from heavy acid rainfalls on the success of numerous breeding birds, possibly due to calcium depletion (i.e., leaching) of the environment.  Acid rain also tends to add sulfates to the soil which is known to increase MeHg production in wetlands, but new evidence has shown that there is also a relationship between high levels of MeHg in upland forests with acidic soils.  Because negative effects of Hg on aquatic ecosystems is well documented, there is reason to believe the same Hg deposition could be having negative effects on forest ecosystems as well.  As MeHg builds up in the soil and leaf litter of forest floors, it is absorbed by invertebrates.  Higher vertebrates, namely forest bird species that feed heavily on the invertebrates containing high levels of MeHg, will likely suffer negative effects (e.g., behavioral changes inconsistent with successful breeding).  In an effort to understand the possible links between environmental stressors, in this case MeHg, and neotropical migrant songbirds within their breeding range, the Biodiversity Research Institute is working to develop an exposure profile to MeHG for breeding birds in NY and PA.

• To do so, levels of MeHg must be derived from soil samples, invertebrate samples, and blood samples taken from the birds inhabiting the same forest habitats.  While seemingly invasive, it is no more harmful on the bird than drawing blood from a human would be.  A brachial vein under the wing is punctured with a small needle and capillary tubes are then filled up with the beads of blood that form.  Once a small sample has been collected, pressure is applied with a cotton ball and the blood quickly clots, closing the puncture opening.  In the photo below, a blood sample is being collected from a Wood Thrush.  Thrushes, in particular, were targets in this study because the previous year's pilot study showed them to contain high levels of MeHg, and there is building evidence that some populations, especially at higher elevations in NY are in serious decline.

• In addition to the blood sampling, all birds were banded, aged/sexed, and standard measurements were taken.  In the top photo below, Maria measures the bill of another Wood Thrush and Melissa collects a blood sample from an American Robin in the bottom photo.  Other species of particular interest, in addition to  thrushes, were vireos and warblers, all birds whose diet is principally comprised of forest invertebrates during the breeding season.

• In addtion to sampling birds caught as part of the everyday banding activities at Powdermill, we also happily assisted Melissa and Maria in capturing birds on nearby Powdermill Run (where Louisiana Waterthrushes were particularly targeted) and also on top of Laurel Ridge at Spruce Flats Bog.  This was of particular interest because they feel that evidence from previous research suggests birds in heavily acidified habitats such as subalpine and bog habitats may be at greatest risk.

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• We even managed to catch a heron of our own that the BRI girls were more than thrilled to opportunistically collect a sample from from.  Again, as a top level predator in an aquatic environment, it likely faces a greater risk from MeHg.  On Friday, June 23, we banded this extremely handsome adult male Green Heron.

• The top down view shows the once sought after plumes from herons and egrets that were used to adorn ladies hats and sold as part of the millinery trade until the birds were finally offered protection under the Migratory Bird Treaty Act instituted in 1918.

• As described in Ralph S. Palmer's Handbook of North American Birds, Volume 1 (published by Yale University Press in 1962), sexes appear similar in all ages.  Like most herons and egrets, however, the soft parts (namely bill, eyes, and/or legs) may acquire brighter colors during the brief span of the breeding season.  The photo on the bottom is a close up of the face, in particular the loral area (the blue soft part in front of the eye).  This bird was sexed based on the exceptionally deep blue/purple lore, glossy black bill, and bright orange yellow eyes.

Last Updated on 07/06/06
By Adrienne J. Leppold and
Robert S. Mulvihill