Avian highlights for the month of
March usually include the arrivals of our first Red-winged Blackbirds,
Eastern Phoebes, and American Robins; our overwintering American Goldfinches
progressively molting into their lemon yellow breeding plumage, and good
numbers of migrant Song and Fox Sparrows and Dark-eyed Juncos. Well,
this year was no exception. EAPH, AMRO, RWBL, Field Sparrow, and
Ruby-crowned Kinglet rounded out the 20 species banded this month, hinting
at warmer days ahead, more migrants, and even breeding birds (PA
Breeding Bird Atlassers - are you ready?!). Song Sparrow (76
banded) and Dark-eyed Junco (64 banded) topped the banding totals this
month.
This adult male Red-winged Blackbird
(a companion shot to the one on our home page) was the first of six caught
this month and, in fact, all were adult males. Similar to the differential
spring migration in Ruby-crowned Kinglets that we've discussed time and
again on this website, RWBL's males preceed females at Powdermill by nearly
a month or more. Not only do we see differential migration among
sexes, but as this case illustrates, it is also common for adults to precede
immatures during migration and in arriving on the breeding grounds.
This phenomenon is true for many species.
Perhaps the Black-capped Chickadee
caught on 12 March
was an early spring migrant, or perhaps it was just a winter resident new
to the Powdermill nets. Whatever the origin of the bird, upon even
a quick glance at the wing and tail, its age was no mystery. While
we admit to finding Black-capped Chickadees among the harder birds to age,
there are some things, about this bird in particular, that made it a clear
SY (second year) and that can be applied across the board for this species.
Most banders know that tail shape
can be useful in ageing birds. Immature birds tend to have more narrow,
pointed tail feathers and adults tend to have broad, more truncate tail
feathers. However, this is also the most common accidentally lost
and replaced group of feathers, often resulting in juvenile or immature
birds having replacement retrices closely resembling those of an adult.
This circumstance is illustrated in the photo below. All but three
of this chickadees tail feathers were lost and regrown at some point during
the winter leaving a stark contrast between the lost and more freshly replaced
rounder tail feathers and the retained more narrow and pointed juvenal
tail feathers. Hence, retained juvenal tail feathers = SY.
Imagine for a moment, though, that
this bird lost and replaced all of its tail feathers, and the replacement
ones were uniformly fresh and truncate. Would you have rethought
your ageing of this bird and considered ASY?
. .
Maybe for a moment, but because
tail feather shape should only be used in conjunction with identifying
a definitive molt limit (or lack thereof) on the wing, we can still make
the correct age determination for this bird as SY. The photo below
highlights the very subtle molt limit among the greater coverts, the outer
two being retained juvenile. Had the wing caused any confusion in
ageing this bird, and since one should never age a bird solely based on
the appearance of tail feathers, we would have aged this bird less precisely,
but not incorrectly, AHY (after-hatch year).
As we mentioned above, we find chickadees
among the hardest species to age because there is frequently a pseudo molt
limit among the outer greater coverts. However, in the case of the
bird above, the molt limit among the outer greaters is real.
While the color does fade a bit distally on the wing, the outer two greater
coverts, and for that matter the retained carpal, alula, and primary coverts,
are identified as retained feathers because of their much more washed out,
worn, and lightly pigmented appearance. Furthermore, we've observed
that retained feathers on members of the tit family (Paridae) will sometimes
be longer than the replaced ones (the step down visible in the photo above
is the opposite of what you might see on a Catharus thrush where
replaced/molted inner greater coverts are longer than retained outer greater
coverts).
For those fortunate to have obtained
a copy of the out of print Moult and Ageing of European Passerines
by Jenni and Winkler, this difference is also shown among their many pictures
of birds from the genus Parus, particularly in Fig. 432 on page
149 for Blue Tit and Fig. 439 on page 151 in the account for Great Tit.
We were very fortunate to have help
from a crew working with the Student Conservation Association (SCA) one
day this month and in return we were more than happy to show them the ins
and outs of bird banding. In the photo below, the crew is getting
up close and personal with one of the many chickadees banded this month.
What a great, hard working crew!
Getting the banding area set up for the upcoming seasons can be quite a
chore...setting up 70 nets let alone clearing and trimming the brush from
the net lanes. Especially since the snow fall last October, there
were plenty of branches that needed clearing. Thank you so much SCA
for your hard work helping us to prepare our net lanes for this season!
The SCA offers programs for high
school students, as well as college internships, that expose and introduce
participants to working within the natural world. The hope is that
these work experiences will instill in SCA participants the ethics of conservation
and inspire in them a lifelong dedication to environmental stewardship.
In this way, the SCA program benefits our society and the environment.
For more information about SCA, please visit www.thesca.org.
As mentioned in the introduction, this adult Field Sparrow
was among the first new species for the spring.
We've often compared bird banding
at Powdermill to Christmas morning. Whether its checking nets or
reaching in the bags and pulling the next bird out to be banded, you just
never quite know what you are going to get. Well, Sunday, March 26
was no exception. Bi-catches, for example, of insects, are always
a part of banding and operating mist nets. But we've also caught
frogs, fish, snakes, bats, deer, chipmunks, squirrels, and even an opossum
in the nets before! Add to the list Meadow Vole--sure, it looks
kind of cute, but...
After losing the first two battles,
bander-in-charge, Adrienne Leppold, managed to win the fight and disentagle
this small rodent (with its very BIG teeth) from the net....and she's still
got the battle scars to prove it.
From the beginning to the end of
the month there was a marked transition in the appearance of the goldfinches
visiting our thistle feeders. The adult male in the top photo was banded
on March 3, still with its basic brown back and whitish underparts, and
without a trace of a black crown. The second year male banded on
March 30 (bottom photo), well along with its first alternate molt, was
showing much lemon yellow breeding plumage on its back and belly, with
black crown feathers replacing the drab olive ones from its first basic
plumage. Another, more subtle seasonal color change in goldfinches
and some other species can also be seen in these two photos--the change
in bill color from mostly dark and dusky to brighter orange (the bill of
the bottom bird will get even brighter).
Lastly, we thank all the volunteers
that helped with March banding: Jessica Scopel,
Keri Parker, Pam Ferkett, and Greg George.
