Summer Season--1st Half
NOTES & HIGHLIGHTS
(7 June-3 July)
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Banding effort in summer is reduced
somewhat to 4-5 banding days per week (down from six per week during migration
seasons). This resulted in 20 banding days during the period.
Daily banding totals ranged from just four birds on June 9 to 24 on June
22. Despite the seeming lateness of the spring migration at
Powdermill, there were no lingering migrants into the early part of the
summer period covered in these notes. Similarly, there was little
or no hint of any fall migratory movement by the end of the period.
Notwithstanding this, there were plenty of signs, even before the end of
June, that the nesting season already is over for many birds at Powdermill
and that it will not be too long before we do begin to detect true southward
movement of migrating songbirds.
.
Thus far this summer we've banded
268 birds of 40 species and
processed an additional 104 recaptures. To date, American Redstart
tops the summer banding list (44 banded), followed by Song Sparrow (38),
Yellow Warbler (16), Cedar Waxwing (14), Red-eyed Vireo (14), and American
Goldfinch (14), and Louisiana Waterthrush (11). Volunteers and visitors
during the period included Carole Shanahan, Pam Ferkett, Randi Gerrish,
Pete Spino, David Liebmann, Reed Peters, Andy Homsey, John Parran, Dr.
Jeff Watson (North of Scotland Director with Scottish Natural Heritage
and author of the definitive The Golden Eagle, published by Princeton
University Press in 1997) and Dr. Todd Katzner (Director of Conservation
and Field Research at The National Aviary)
.
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Totals given above for Song Sparrow
and Louisiana Waterthrush reflect additional banding effort in connection
with two research projects at Powdermill. A new study of Song Sparrow
molt biology was initiated by Grace Greenwood (pictured below), a Master's
student at Georgia Southern University. Grace's advisor, Dr. C. Ray
Chandler, is a Powdermill Avian Research Center Research Associate who
has worked with us at on a variety of research studies over the past fifteen
years. The most recent of these examines consequences for wing morphology
of variation in the extent of the highly variable first prebasic molt in
hatching year (HY) SOSPs. Our paper currently is in press in the
Journal
of Avian Biology, and Grace's graduate research study is designed to
assess possible factors, such as hatching date and body condition, that
may influence observed variation in extent of this molt. In
the photos below, Grace bands fledgling and nestling SOSPs on her study
plots.
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Additional Louisiana Waterthrushes
continue to be banded at Powdermill each summer in connection with what
now is a long-term (this is our tenth consecutive season) study of its
breeding and population biology, specifically to monitor effects of acidification
(by acid rain and/or abandoned miune drainage) of the forested headwater
stream habitats required by this specialized riparian songbird. Jessica
Maggio (below), a graduate of St. Mary's College in Maryland, is our Netting
Environmental Fund (of The Pittsburgh Foundation) intern working on the
waterthrush study this summer. Her work involves monitoring the activities
of up to twelve nesting pairs on two streams. One of these streams,
Powdermill Run, is exceptional quality and supports maximum nesting densities
of the species, while the other is degraded by acidic abandoned mine drainage
and supports only a small fraction of the number of nesting pairs found
annually on Powdermill Run. In the photos below, Jessica bands a
ten-day old LOWA nestling.
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Although it hasn't affected our
banding totals for the summer, work being done by another intern, Emma
DeLeon (below), working at PARC under a Brackenridge Fellowship from the
University of Pittsburgh Honors College has been a valuable addition to
the avian research activities at PARC. Emma, under the direction
of her faculty advisor, Dr. Tony Bledsoe, has been working closely with
Mike Lanzone, PARC's Assistant Field Ornithology Projects Coordinator,
to record individual variation in flight call vocalizations of wood warblers
after banding, to analyze acoustical data (continuous recordings of the
flight calls given by nocturnal migrants flying over Powdermill in spring
and fall) collected over the past several migration seasons, and to study
vocalizations given by wood warbler young and their parents at or
near their nests. In the photos below, Emma holds a Kentucky Warbler,
places it briefly in a fabric acoustical recording cone, and analyzes (with
Mike) the spectrograms of some recorded flight call notes. For some
more information on intern projects at Powdermill, go to www.powdermill.org/research/avian.htm
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We'll start the pictorial highlights section of this update
with photos of two "side-burned" warblers, Kentucky (left photo; same bird
being held by Emma in the photo above) and Yellow-throated (right photo),
netted during the period. Both birds were aged SY, and the KEWA,
in particular, was in comparatively high plumage for his age; the YTWA
was a recaptured bird (from earlier this spring), so it does not appear
in the table of banding totals for this season.
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Birds in beginning to middle stages of their definitive
prebasic (sometimes called post-nuptial or post-breeding) molt already
were showing up in our nets by mid-June. This included Yellow Warbler,
American Redstart (an early molting SY male banded on June 13 is pictured
below), and Black-and-white Warbler. These earliest molting
birds likely are failed or non-breeders. By accomplishing their molt
2-3 weeks earlier, they probably will be in a position to depart the breeding
grounds well ahead of individuals of their species that bred successfully.
This is because the added energetic and nutritional demands of molt (as
well as reduced aerodynamic performance) typically select for minimal overlap
between it and any breeding (nest building, egg laying, incubation,
and care of nestlings and fledglings) or migratory activity.
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The importance of molt for preserving the insulatory and
flight performance of feathers, which become increasingly worn over time
due to exposure to sunlight, physical abrasion, and feather degrading ectoparasites
and bacteria, is particularly obvious in summer. Adults of most songbirds
undertake the only complete molt of their plumage for the year immediately
following the breeding season. This means that during summer, prior
to the onset of this molt, their feathers are in their most worn condition
(especially those not replaced during the recent prealternate molt).
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Individuals can vary greatly in the degree of wear,
depending on the habitats they have used, the environmental conditions
they've encountered, and the parasite loads they've experienced.
In the case of second year (SY) birds, any retained juvenal feathers will
be among the most heavily worn feathers seen by banders at this time of
the year. This is because those feathers had poorer structural integrity
in the first place (being less heavily pigmented and more lossely knit),
and because they have been exposed to wear for a year or more, from the
time they were first grown in, beginning when the birds were nestlings.
Pictured below is a good illustration: the extremely
worn retained juvenal rectrices (especially the very exposed central pair
of tail feathers) of an SY female Baltimore Oriole banded on June 12.
More subtle is the contrast between the very worn grayish retained first
basic head feathering of an SY female Northern Parula banded on June 19,
compared to the less worn, more bluish alternate feathers on the forecrown
that were included in an unusually limited prealternate molt by this bird
earlier in the spring.
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At first glance, it appeared as though an SY male Scarlet
Tanager banded on June 14 might already have started its definitive prebasic
molt, the molt which results in the change from a bright scarlet orange
breeding plumage to a much duller olive and yellow non-breeding, or basic,
plumage. Closer examination, however, revealed it to be a case similar
(but certainly not as subtle!) to the NOPA above. The yellow underparts
(bottom photo below) and scattered olive green feathers above (top photo)
are, in fact, basic feathers retained following an abnormally incomplete
prealternate body molt in the case of this individual. The wear differences
between the two feather generations are more evident in the case of the
back feathers, because these are more exposed to the feather-degrading
effects of UV rays from direct sunlight.
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The photo below shows another interesting contrast between
orange and yellow feather coloration. AMRE males have a plumage sequence
that is characterized as "delayed plumage maturation," which means that,
unlike most other songbirds, immature male AMREs do not have in their juvenal
plumage, and do not acquire after their first prebasic or first prealternate
molts, significant adult male-like plumage characteristics. Instead,
they remain female-like in outward appearance (including yellow tail spots)
through the end of their first breeding season as adults. It is during
their second, definitive prebasic molt that they acquire the jet black
and bright orange coloration we associate with males of this species (if
you think about it, it's the reverse case of the "confusing fall warbler!")
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This SY male American Redstart, however, adventitiously
replaced half of its juvenal tail. Thus, even when juvenal
tail feathers are molted prior to their normal molt, they nonetheless are
replaced by feathers that have a strong suggestion of the fully adult male
coloration. And, as has been shown on this website many times
before, examples such as this also can be instructive as to the difference
in rectrix shape between juvenal and non-juvenal feathers, the former being
more acutely pointed at the tip (second photo below).
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In a different case, the fully grown adventitiously replaced
feathers of an ASY female were deficient in carotenoid pigmentation and
also were abnormally short. Apparently, this bird was more nutritionally
and/or energetically stressed when its replacement tail feathers were growing
in.
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The pictures below show an example not of a difference
between age classes in the occurrence of red color, but rather in the location
of it in the plumage. Caught together in the same net, the juvenile
and adult male Downy Woodpeckers pictured below both have red head feathers.
These feathers occur on the crown in males in juvenal plumage and on the
back of the head (the so-called "nuchal patch") in adult males. Of
course, the softer, grayer plumage and much shorter bill also serve to
distinguish this juvenile from its parent.
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Continuing the color theme that seems to have taken over
this update, we go from red to ruby red. Fully half of the Ruby-throated
Hummingbird banded during the first half of the summer season have been
adult males. This is an unusually high percentage for this species
in which adult males suffer disproportionately high mortality during the
breeding season because they have much smaller body mass than females and,
therefore, cannot endure periods of unseasonably cool or inclement weather
as well. The early summer at Powdermill has been unusually warm,
with daytime temperatures consistently in the high 80°s or low 90°s
throughout most of June and overnight temperatures rarely dropping below
60°F.
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Midway through the period covered by this update, Powdermill
conducted its fourth annual BioForay, a joint research and education project
designed to assess and monitor patterns of biodiversity on a large (ca.
75 acre) study plot at Powdermill (Powdermill comprises 2,200 acres in
all). As in the past, more than 30 scientific experts in taxonomic
specialities ranging from springtails to slugs and snails to flowering
plants and ferns to mosses and lichens to beetles, butterflies, and moths
and to birds (of course!) are joined by 30-40 enthusuastic "avocational
naturalists" who relish the opportunity to spend time in the field assisting
the experts and learning the correct methods for scientifically sampling
and identifying plants and animals of many kinds.
The theme for this year's BioForay, "You never
know what you will find...," was in honor of the exciting discovery that
Ivory-billed Woodpeckers are alive and, we all hope, doing well in some
extensive tracts of remaining old growth swamp forest in Arkansas.
Powdermill's own Mike Lanzone was among those assisting with the search
for the Ivory-bill and among the few involved with the search who actually
sighted one (you can read about Mike's Ivory-bill experience in the current
newsletter of the 2nd Pennsylvania Breeding Bird Atlas--click on PennsylAvian
Monitor under "Recent News").
In addition to incorporating an Ivory-bill image (drawn
by Carnegie Museum's Jane Hyland) on the official BioForay 2005 t-shirt
(design shown below), we made something of a contest out of who could find
an Ivory-bill somewhere on the 75-acre BioForay plot.
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A fairly realistic Ivory-bill cutout decoy (photo below)
finally was spotted (near grid post I-4; "I-4"y-bill--get it?!) in the
waning hours of BioForay 2005 by sharp-eyed avocational naturalist, Linda
Hess.
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Finally, those of you who follow this website on a regular
basis know that Powdermill's Bander-in-Charge for the past year and a half
has been Adrienne Leppold. In addition to very capably running the
banding program while Bob Leberman has pursued his semi-retirement and
Bob Mulvihill has focused primarily on coordinating the 2nd PBBA, Adrienne
also did an excellent job as stand-in webmaster for this site through mid-spring
of this year when she left Powdermill for a short time to serve as a field
supervisor in a study of nesting seabirds on an island in the Maine Coastal
Islands NWR system. Adrienne has extensive experience studying seabirds
in Alaska, but she has always wanted to work on this study of nesting terns
off the Atlantic Coast. Well, Adrienne's working sabbatical away
from PARC will be over in another few weeks, when she will again return
to take over the reins of the banding program and this website. Undoubtedly,
she will bring back with her some exceptional pictures from her experience
and will share some of these on this website. Until then, we want
to share some excerpts from a recent letter she wrote to the PARC staff:
Hi All,
Island life is pretty great. Migration was phenomenal!
I couldn't believe the fallout of warblers, thrushes, flycatchers, all
feeding amongst the same rocks in the tidal area (right in our backyard)!
As far as the seabirds, it''s been really nice to be back on the coast.
Mainly just terns, gulls, and guillemots on our island, but we got to help
out with some censuses on other islands last week and saw tons of razorbills
and puffins, seals, and even a minky whale! We have tern chicks popping
out everywhere...[I'm] trying to avoid as much pooping and pecking as possible.
I've decided I can identify species just by how hard they hit. Common
Terns are fierce!, but I'm loving every minute of it.
Can't believe how fast it's going by. Only three weeks left on the
island. I'll be back at Powdermill before you know it.
--Adrienne
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Hurry Back, Adrienne! Warbler "chicks" are popping
out everywhere here!
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Last Updated on 07/07/05
By Robert S. Mulvihill
