A West Virginia University graduate student was recognized for her research into wild bird populations by the Association of Field Ornithologists.
Crissa Cooey, a doctoral student in WVU’s Division of Forestry and Natural Resources, took first place in the graduate student poster competition at the association’s recent annual meeting. The award was given for her presentation on age and gender population demographics for Double-crested Cormorant populations living around the Door Peninsula of Wisconsin.
Cooey was previously honored by the Wildlife Society for work that explored methods of determining a bird’s age, which provided the foundation for this current field work.
“Once birds become adults, it is impossible to tell how old they are,” Cooey continued. “Their feathers don’t turn gray like hair does for mammals. You can’t age them by wear of teeth because they don’t have any teeth. Their skin is completely covered by feathers, so you can’t see any wrinkling.”
“It’s notoriously difficult to determine a bird’s age,” said Hillar Klandorf, a professor of animal physiology in the Davis College of Agriculture, Natural Resources and Design and one of Cooey’s advisors and collaborators. “The traditional method of determining the age of birds is through banding, and that’s very labor intensive.”
Cooey found that the least intrusive means of obtaining a usable sample was to take it from the patagium, a fold of skin that makes up the leading edge of a bird’s wing. She then closed the wound using a special tissue glue. Recovery time was shorter for these birds than other methods, and the samples offered accurate information on their ages.
“Since then I have taken the live sampling technique to the field, but I have also looked at other population demographic parameters as well,” Cooey said. “My main research objectives were to determine if management practices of Double-crested Cormorants around the Door Peninsula were causing a shift in survival and fecundity for various age classes of the bird.”
Cooey and colleagues from WVU and the USDA’s National Wildlife Research Center Mississippi Field Station, Horicon National Wildlife Refuge and Wisconsin Wildlife Refuge surveyed four field site islands in 2010 and 2011. Hat and Jack were the managed islands where egg oiling occurred both years to prevent the eggs from hatching, and shooting occurred in the second year to reduce the number of breeding birds on the island. Spider and Pilot were the unmanaged islands.
“We trapped birds using modified leg hold traps and took skin samples and blood samples from them before they were banded and released,” Cooey said. “The skin samples were analyzed for pentosidine concentration. Once the concentration was established, age was estimated using the age prediction model.”
A total of 276 birds were sampled. The unmanaged islands had a larger population of younger adults breeding on the islands. The managed islands had more middle aged adults breeding on the islands. This suggests that there is an age shift of breeding birds based on management practices.
Blood samples were analyzed to determine the gender of the birds. More males were sampled on Hat, Jack, and Pilot islands. This suggests that males were found to be more tolerant of management than females.
The recognition of Cooey’s work by the Association indicates a new wave in wildlife population research.
“One of the primary limiting factors for modeling avian population changes has been the inability of biologists to correctly age birds beyond general categories of adults and juveniles,” said Jim Anderson, one of Crissey’s advisors and a professor of wildlife and fisheries resources at WVU.
“The continued development and refinement of this technique by Crissa will improve the ability of wildlife managers to effectively conserve and manage wild bird populations,” Anderson added. “It is indeed a significant accomplishment for Crissa to be recognized for her novel research contributions by the AFO and I am very proud of her efforts.”
The Association of Field Ornithologists is one of the world’s major societies of professional and amateur ornithologists dedicated to the scientific study and dissemination of information about birds in their natural habitats.