Update

We have been unable to complete fieldwork for over a week due to constant snow and/or winds that kept us from going out in the zodiacs. However, on Wednesday the weather finally cleared and we began work at the abandoned penguin colony on Lagoon Island a few miles from the station. We excavated a 1x1 meter square to sample this site, similar to how we sampled the active penguin colony on Ginger Island last week. We excavated in 5 cm levels and screened all the sediments on the beach using buckets of seawater.

We stopped digging after reaching a depth of 30 cm as our pit was filling with water seeping in from snowmelt. However, we recovered quite a few penguin bones (see photo) many of which are from small chicks indicating that these birds were born on the island. What was unusual, though, was that we were not finding the hundreds of eggshell fragments that characterize other abandoned colony sediments. Either this site is not an abandoned colony and the bones accumulated in some other manner, or the eggshells had not preserved. We will have to look carefully at our screened sediments and the organic material we've recovered to better understand this deposit.

Click on photo to take a closer look at the penguin bones

On bad weather days, we spend our time in the lab looking through our samples. Over the past week, we have been studying the material collected from the modern colony on Ginger Island. This sediment is rich in penguin bones, eggshell fragments, fish bones and otoliths (fish ear bones), and squid beaks.

The otoliths in particular are important as they can be identified to the species of fish they came from. In addition, they preserve well in the sediments and pass through bird stomaches essentially undamaged. With the samples from Ginger Island, I'm already noticing a lot more fish otoliths from this colony than I've found in other sites in the Peninsula. While I still need to quantify this observation, it may be that the penguins on Ginger Island are feeding on fish more heavily than penguins at other locations in the Peninsula. If so, it may be due to poor krill availability in this area or other, unknown factors. As with most science projects, new questions always arise while collecting your data--that's what makes it so interesting and stimulating.

In addition, science also requires that you are flexible in your research. We came to Rothera hoping to find lots of abandoned penguin colonies. We need to survey the exposed ground surface to find these sites and these areas are usually snow-free by this time in the Antarctic summer. Unfortunately, there has been more snow persisting this summer than usual. In fact, I've been told that last summer at this time the station had little or no snow cover left on the islands and other areas that normally would be exposed. So, the snow cover has hindered our search for abandoned colonies and we have found only the one on Lagoon Island. However, to make the most of our limited time here we are developing other projects.

One such project that also relates to climate history in the region involves the study of raised beaches (see photo). These beaches were formed during periods of higher sea levels in the past, when the earth's climate was warmer than today. At Lagoon Island, there are three beaches visible: the modern beach, and two successively higher beaches formed of cobbles, pebbles, and sand. In the photo, the lines point to each of these beaches with the modern beach on the far left. The highest beach on the right is the oldest and is approximately 2.6 m above current sea level. If we can find organic debris buried in this beach, such as old scallop or clam shells, we could obtain a radiocarbon date and know approximately when sea level was at this height.

Click on photo to look closer at the Raised Beaches

In addition to looking at these raised beaches, we also have been studying the diet of the skuas (flying birds related to gulls) that live on Lagoon Island. There is a large population there, at least 50-75 breeding pairs. Another island nearby has about 100 more breeding pairs. All these skuas must be supported by a rich food supply nearby and we suspected that this food consisted primarily of fish, especially Antarctic silverfish, one of the primary diet items of skuas in other parts of Antarctica. So, the other day Jenny and I went around to the skua territories on Lagoon and scooped up feces samples for analysis. We collected 50 samples, using a spoon and plastic bag, and then washed these samples through fine-mesh screens.

Although it doesn't sound very fun, what we recovered was quite interesting--dozens of otoliths representing the fish these birds have been eating. We will collect another sample next week and track the diet of these birds during our time here. It adds one more piece of information on the ecology of seabirds in this part of the Peninsula.

Questions, Comments
email David Hughes, djh6183@uncwil.edu
Last updated February 29, 2000