Update #3
6-12 Jan. 2003
We have had a busy week here. Because the weather has been relatively mild,
with no storms, we've been able get out in the field often and collect samples
from abandoned colonies near the station. The more I go out, the more
of these sites I find in this area. It raises the question as to whether
or not all these abandoned sites were occupied at the same or different times
in the past? If they all date to the same age, it would indicate a substantial
increase in the number penguins that were breeding here compared to today.
At present, there are approximately 105,000 breeding pair in this region (Windmill
Islands and coast; see map at (Windmill.pdf) and
that number has been increasing since the 1960s, according to my colleague,
Dr. Eric Woehler, who has been studying the penguins here for many years.
So, the abandoned colonies could reflect an even larger number of penguins that
were here at some time in the past. I'm anxious to sample a number of
these sites so that we can obtain radiocarbon dates on them and start finding
some answers to these questions.
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| One of our abandoned colonies near a radio
antenna (back left) on west Bailey Peninsula. Note also the pebble mounds
behind this site where other abandoned colonies are located. |
When we're not out sampling sites in the field, we are in the lab processing the
sediments that we excavated from the sites. These sediments contain the remains
of penguins that died on the colonies in the past, plus any food remains that
passed through the gut of the penguins and was deposited in the colony from their
guano. Fortunately, after hundreds of years, the guano no longer smells
bad and is completely degraded into the sediments. So, we can find remains
of the fish and squid that the penguins ate in the past as well.
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| Michele washing sediments in the lab. |
Steve checks over the sediments drying in trays
after washing. |
To extract all the organic remains from these sediments, we begin by
washing them through three screens with mesh sizes ranging from 1/4 inch to
very small openings at less than 0.001 inch. These screens sort the various
sizes of rocks and organic remains from the sediments while washing away the
fine silts. Then, we can quickly look through the pebbles trapped by the
top screen to recover any bones there and throw the pebbles back outside.
The second screen contains more gravel-sized rocks. These we dry and sort through
in the lab using a low-power magnification lamp and we often find small pieces
of penguin bone and eggshell, fish bones, and squid beaks. Once sorted,
we can discard these rocks back outside as well. Now we've reduced the
overall weight of the sediments considerably and the finer sediments from the
last screen will have to be shipped back to my lab in Wilmington to sort under
a low-power microscope. It is in these sediments where we'll find more fish
bones, otoliths, and other organic remains that will tell us the most about
penguin diet in the past.
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| Steve sorting through washed gravel-sized sediments
to recover small bones, eggshell, and squid beaks. |
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| Penguin bones and eggshell fragments recovered from the sediments
from an abandoned colony. |
Yesterday we visited a new area for us since we arrived here. We had an opportunity
to go down the coast by boat and visit Hall Island, a large island with over 10,000
pair of Adélie penguins currently breeding there. The island is rocky, with
lots of hills and ridges, and even has a few small lakes formed by snowmelt.
The penguins are breeding primarily on the ridges which become snow free from
the winds early in the season. Near the active colonies, there also are mounds
of pebbles from abandoned colonies. Another person studying the birds here,
Frederica Oliver, showed us where she had found many of these sites. There are
lots of abandoned colonies here, probably at least 20 of which some look fairly
old. So, once again, we have an area rich in penguin history that I hope
we can sample while we are here.
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| Abandoned and active penguin colonies on Hall
Island. Note the chicks in the right photo, only a few weeks old. |
My next update will provide more information on our next excavations.
Steve Emslie