25 October 2009

Analysis of Trumpeter Swan Habitat Underway for Greater Yellowstone Region

Research is currently underway in the Yellowstone National Park region to understand habitats features of breeding habitat available for the majestic Trumpeter Swan, the largest swan in the world.

Laura Cockrell - a Master's program student at the Department of Biological Sciences of Eastern Kentucky University - is evaluating the "Historical Nest Site Use by Trumpeter Swans in the Greater Yellowstone Ecosystem."

The study revolves around the use of LANDSAT imagery in an "attempt to find ideal Trumpeter Swan nesting habitat based on the spectral reflectance" shown by the aerial images of habitat conditions, Cockrell said. This analysis includes a comparison of recent and historic images to "determine if the satellite images can be used to detect changes in the habitat over time. We are trying to see if the LANDSAT images can determine habitat features that have changed over time, which would cause the swans to abandon previously used nesting sites."

Laura Cockrell, with Grizzly Lake (one of our territories sampled) in the background. Images courtesy of Laura Cockrell.

Laura Cockrell, in an orange safety-vest worn when sampling in the eye of the public; in this case, along the roadway where Pelican Creek meets Yellowstone Lake.

"I plan to discern differences between historically used ponds and currently used ponds, and to identify local and landscape-level features that may have changed over the years and influenced the nesting preference and success of breeding Trumpeter Swans," Cockrell said in her research proposal. Information derived from the satellite imagery will be further evaluated, based on on-site evaluations conducted during the field studies phase of her research, that will include measuring vegetation, food availability, distance from the nesting pond to nearby ponds, water quality and an evaluation of the extent of lead present at nesting sites.

"The Yellowstone nesting population of Trumpeter Swans has decreased a great deal in the last few years, to the point that only three pairs of Trumpeter Swans occurred in the park" in 2009, with only one pair attempting to nest, she explained in an email.

"Although it has been long thought that the population that is nesting within the park is a sink population, which relies on populations in higher quality habitat outside of the park as the source population, there is still an interest - primarily fueled by bird watchers - in why the Yellowstone Park nesting population has declined."

Weather is a prominent, potential factor.

"Currently the Palmer Drought Severity Index shows that the Greater Yellowstone Region has been in an extended drought, which is likely a factor in the decline. Nesting populations outside the park have also recently seen reductions in nesting attempts as well as cygnets produced."

During July this year, Cockrell, and Matt Manuel, the research assistant, traveled to Yellowstone to sample habitat characteristics of sites historically used by Trumpeter Swans. Line transects were used to evaluate aquatic vegetation in 16 former swan territories, she said. The next onsite visit will be during late August and early September, 2010, when 20 territories can hopefully be sampled.

"I am using the UTM coordinates of line transects to determine the reflectance characteristics of the LANDSAT images and evaluate whether the LANDSAT reflectance is capable of determining" the suitability of the habitat for swans.

By mapping nesting locations and characteristics of "used" versus "potential" habitat, her research can be used to identify potential nesting sites. This information is expected to be a "valuable tool" for achieving objectives for management of the Trumpeter Swan in the Greater Yellowstone ecosystem.

An example of LANDSAT imagery showing Trumpeter Swan habitat. This is an image of the "undisclosed location" where the swans attempted to nest during the summer of 2009.

If the research works as planned, "it will allow the park an easy method to track the quality of nesting locations," she said. "As the park does not actively manage for wildlife, but instead attempts to have a 'hands-off' approach to allow nature to take its own course, no management efforts are in place to improve or create nesting sites within the park. If conditions continue to change in an unfavorable manner, it is possible that resident swans could leave the park entirely, however this tool could help park biologists to monitor locations for potential future nesting swans. We certainly hope that natural conditions will change in time that the swans will again be successful within the park, however we cannot predict how the conditions will change.

"If this tool does work, managers of areas outside the park (e.g. Red Rocks Lake NWR) can use it to locate suitable nesting habitat, as well as locating suitable habitat outside of managed areas that could potentially be preserved. As the park population is thought to be a 'sink' population, with the breeding population outside the park as the 'source'. If these sites can be located and managed appropriately, there will be a greater number of swans looking for potential breeding sites in the future, and hopefully moving back into the park as conditions improve.

"As the Greater Yellowstone Ecosystem is linked as a whole, it will be beneficial to evaluate these locations and protect them from development or degradation. The trumpeter swan was brought to the brink of extinction, and the Greater Yellowstone population has been critical in bringing the entire trumpeter swan population back to stable levels. Through management efforts within the GYE, we are now seeing relocation and breeding efforts in the US and Canada trying to restore populations in historical areas, including much of the mid-west. If we can fine-tune this tool to locate these ideal sites, it could potentially assist agencies who are attempting to find suitable relocation sites for their population restoration efforts.

Her biological research with the Trumpeter Swans is a continuation of Cockrell’s interest in studying waterfowl, which started with a college course.

"I became interested after working in my undergrad at California State University, Chico (my hometown college) where I took a natural History course on waterfowl from Jay Boggiatto, Cockrell explained. Under Professor Boggiatto, "I worked on a wintering ecology project with American and Eurasian Wigeon, as well as working for the California Department of Fish and Game, monitoring for waterfowl die-offs during the winter and Wood Duck monitoring during the spring and summer. I also worked for the California Waterfowl Association banding ducks in the Sacramento Valley."

The swan project was started by her adviser, Dr. Robert Frederick, whom did work similar to this during a sabbatical in 2006, working with Rick Sojda from the United States Geological Survey. "My graduate work is a continuation of the work that he began which originated by trying to find appropriate wintering locations for trumpeter swans in the Greater Yellowstone Ecosystem."

A trumpeter swan research sign posted in the Targee National Forest, just south of Yellowstone Park.

An "undisclosed" location where trumpeter swans attempted nesting this year. The birds are visible in the distant background.

The trip to evaluate swan habitat at Yellowstone Park last summer, was her visit, Cockrell said. "It was an amazing experience, especially working for over three weeks. The majority of park visitors never travel through the back country, whereas the majority of our work took us through back country hiking trails. We sampled across virtually every area of the park this year, and I look forward to traveling back to the park next year and seeing an entirely different season of the park, as well as new sampling locations. Traveling through areas such as the Lamar and Hayden Valleys were incredible with the amount of wildlife present. We were forced to re-think our travel plans more than once because of wildlife (such as a bison 'surprise' or grizzly kill along a hiking trail)."

"We went into this project not expecting to encounter any of the swans, however we were excited to see a total of five trumpeter swans during our trip; one pair that attempted nesting and failed, one pair that did not attempt to nest, and a solitary swan who has lost its mate and has not yet re-mated (we did not locate the third pair during our trip this year). It was rather bitter-sweet to see the swans - they are beautiful birds but it was sad to see them knowing that no cygnets were produced. The solitary swan prevented us from sampling the territory since drought conditions have shrunk the pond it was on to a size where we could not sample without disturbing the swan, which would have violated park policy. In all of our swan sightings, we were very careful to minimize any potential disturbance that would cause the swans to abandon their chosen territory.

"It was definitely an incredible journey!"

A $10,000 grant from the Yellowstone Foundation was provided for this research to fund a stipend, and to pay for lodging and travel and field equipment, and for which Cockrell is very appreciative.

Staff at Yellowstone National Park were also very helpful: "Thanks to Dr. Doug Smith of YNP for his help coordinating my field research and funding, and to Christie Hendrix from YNP permit office, Lisa Baril, Leslie Henry, and Josh Irving (all of YNP) for their assistance with field work. A big thanks to Matt Manuel, who was my field assistant during the entire trip, and to Dr. Frederick - my adviser at EKU." Additional financial support is being provided by Eastern Kentucky University.

A final report for this project is expected in October 2010.

Cockrell hopes to continue working with waterfowl following the completion of her thesis research and coursework at EKU.

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