 Radio Script 2001 __________________ Kittiwake Contrast
STORY: Saint George Island is a 12-mile-long promontory in the heart of Alaska's Bering Sea, some 300 miles north of the Aleutian Island chain. Saint George's steep cliffs make perfect nesting places for millions of red- and black-legged kittiwakes. In fact, 80 percent of the world's kittiwakes make Saint George their home. In recent years, however, Saint George's kittiwake population has been declining. Scientists theorize the declines may be linked to dramatic changes in the productivity of the Bering Sea that has made food harder to come by. Yet, to the south, a much smaller population of kittiwakes seems to be thriving on Bogoslof Island, a one-mile long dimple in the vast sea. Vernon Byrd, a biologist with the U.S. Fish and Wildlife Service, is among a cadre of scientists trying to find out why seabirds are doing well in one place but not the other. BYRD: "The idea was to take a look at how kittiwakes are responding to environmental conditions. Our objective was to contrast populations at two locations that are geographically close together in the Bering Sea, but that had different oceanographic characteristics and had historic population trends that were different." Although both islands are in the Bering Sea, that's about all the two have in common. While Saint George sits atop the outer continental shelf, where the water is relatively shallow, Bogoslof teeters atop water thousands of feet deep. Here, upwelling currents bring nutrients and fish to the surface, where they're easy prey for hungry kittiwakes. BYRD: "We've seen populations change like this. The question is why. The next step is to look at productivity at the site where they have increased. In other words, if it's very different at Bogoslof then we can conclude that the food web is somehow not affected by the same things that have caused it to be less productive for the kittiwakes around Saint George. So, it will be a series of these comparisons that will ultimately allow us to understand the ecosystem processes that cause these changes." While some researchers have focused on capturing, measuring and banding chicks, others have set their sights on understanding just what kittiwakes are eating—to see if there are differences in kittiwake diet between the two islands. They could do this the old-fashioned way—by killing dozens of seabirds and examining their stomach contents. But Sara Iverson, a physiologist at Dalhousie University in Nova Scotia, Canada, has found a better way. IVERSON: "I've found that fatty acids, which are sort of the building blocks of fat, can reveal a great deal of information about an animal's diet, especially as you move up the food chain. There are roughly about 70 fatty acids that can be identified. They differ basically according to ecosystem and species feeding habits. So what happens is you get herring that feed on one sort of diet, and you get pollock that feed on another. And because fatty acids travel up the food chain intact, the fat that is stored in the predator begins to reflect and look like a mixture of what it's consuming in its diet." Without killing the seabird, Iverson is able to pluck a small amount of fat from the bird. The fat sample is sent to a lab where technicians produce a profile of the fatty acids contained in the seabird's tissues. From that, she can tell what the seabird ate—not just that day, but over the last several weeks. IVERSON: "For stomach contents, you have to kill the animal, and it only gives you a snapshot of what it's recently eaten, not necessarily what it's been making a living by. Fatty acids provide an integration of diet over a longer period of time. We're trying to use this as a tool to see what these birds are doing in these different areas." Of course, before researchers could examine a piece of seabird fat and tell you what it's been eating, they first had to measure the fatty acids of the seabird's prey. This gave them a kind of fingerprint to look for. IVERSON: "It's kind of a pattern-matching issue. You take a fat sample from the predator and try to figure out what types of species it's eating and what levels of species it's eating." Sara Iverson and Vernon Byrd say understanding the diets of the two seabird colonies will go a long way toward understanding how the Bering Sea ecosystem works. Their project is funded by the North Pacific Marine Research Program, established by Congress to pinpoint the causes of Bering Sea changes and species declines. They say scientists will monitor the production of chicks and their growth to see how the two colonies fare over time. OUTRO: This is Arctic Science Journeys Radio, a production of the Alaska Sea Grant Program and the University of Alaska Fairbanks. I'm Doug Schneider. Audio version and related Web sites (sidebar at top right) Thanks to the following individuals for help preparing this script: Sara Iverson Vernon Byrd Arctic Science Journeys is a radio service highlighting science, culture, and the environment of the circumpolar north. Produced by the Alaska Sea Grant College Program and the University of Alaska Fairbanks.
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