We took blood samples from least auklets caught during Seabird Summer Camp last year. These blood samples were spun (using a centrifuge) to separate the plasma from the red blood cells, and frozen plasma samples were sent to Dr. Sasha Kitaysky at the University of Alaska, Fairbanks (UAF) for analysis of Corticosterone levels.
Corticosterone (also known as CORT) is a hormone that is produced in the adrenal glands. CORT is produced during periods of stress, and researchers have figured out that levels of CORT in the blood of seabirds can tell us how hungry they are. If CORT levels are high, then birds are hungry and local food availability is low. If CORT levels are low, then birds are finding plenty to eat. Learn more
Figuring out the amount of food available to seabirds is complicated. The amount of food available to seabirds depends on many factors, including the depth and density of prey, and the distance of prey from the colony. Measuring zooplankton and fish availability in the ocean also costs a lot because it requires lots of boat time and expensive equipment.
Measuring CORT levels in birds caught at the colony is a much cheaper and easier method of determining local prey availability. We’ve learn all about Seabirds as Indicators of the Marine Environment, and the amount of CORT circulating in the blood of breeding seabirds has become one of the tools that biologists use to understand changes in the marine environment and the resulting effect on the food that seabirds eat.
Dr. Kitaysky and students analyzed the plasma samples during the winter, and student Alexis Will recently met with students via SKYPE to explain the results. Dr. Kitaysky has collected Least Auklet blood samples on the Pribilofs for many years, and this long-term collection has shown that CORT levels increase with local water temperature. CORT (stress) levels are lower when local water temperature is cold. Least Auklets eat zooplankton, and there are more zooplankton for the birds to feed on when ocean conditions are cold.
The collection of the 2013 blood data added to Dr. Kitaysky’s long-term data set and our understanding of the relationship between CORT levels, water temperature and food availability. Check out the results here.
Casper Merculief, 6th Grade
“Alexis Will taught our class and the 7th and 8thgraders about corticosterone on Skype. First she talked about CORT being an indicator for the stress levels in a bird. Soon after, she showed us a graph of the amount of CORT in the birds of St. Paul and St George over one summer. St. Paul had high CORT levels but St. George was still really close. She also talked about how colder waters means less stress on the birds. Lastly, she told us the causes of the stress; hunger, pollution, environment disturbances, and predators. It was fun skyping with Alexis and learning about CORT.”