Tracking Seabirds using Geolocation Data loggers; an interview with Rachael Orben, PhD student at University of California, Santa Cruz. Seabirds spend the majority of their lives at sea searching for food. Knowing where birds go during both the summer and the winter is important for understanding where birds find food and what regions of the ocean are important for seabirds.
Geolocation loggers are tiny electronic devices that have a sensor that records light levels and an internal clock. The time of sunrise and sunset can be determined from light levels, and this information allows researchers to calculate the location of the bird (latitude and longitude).
What is your job? I am currently a graduate student studying for my PhD in Ocean Sciences at the University of California Santa Cruz. As part of my degree I spent 4 summers on the Pribilof Islands using geolocation loggers to track the winter migrations of black-legged kittiwakes, red-legged kittiwakes, and thick-billed murres.
Why do people study seabird movement with geolocators? These geolocation loggers are incredibly small and can be attached to leg bands for long periods of time, which gives scientist the unique ability to study the winter migrations.
What question are you most interested in? I am most interested in how these small seabirds are able to survive and find food in the harsh winter conditions of the Bering Sea and North Pacific.
How do you study these questions in the field? Geolocation loggers are able to tell us about where birds go. However, to actually get the data you have to find the bird that is carrying the geolocation logger a year later and re-catch it! Luckily, like most seabirds, kittiwakes and murres return to the same nest and ledge year after year, but catching a bird the second time is always harder than the first. We used a number of methods to recatch birds including a noose pole, nest snares, and a net gun.
What’s the most exciting or interesting experience you’ve had studying seabird movement? Before we started using geolocation loggers to track birds from the Pribilof Islands no one had any idea where these birds spend their winters so I find plotting every track exciting. It is incredibly impressive to see how far some of the kittiwakes traveled. About 1/3 of the Pribilof black-legged kittiwakes winter in the western North Pacific close to Japan.
Map showing where black-legged kittiwakes that breed on the Pribilof Islands spent their winters between 2008-2011. Red indicates areas where most time was spent.
The first time that I plotted the tracks from the red-legged kittiwakes I almost didn’t believe what I was seeing. These birds actually remain in the Bering Sea for most of the winter, but most of them traveled north and then west to the coast of Kamchatka before returning to the Pribilofs.
For Pribilof black-legged and red-legged kittiwakes there is almost no overlap in where these species winter which is really interesting since these species do share foraging areas as well as the cliffs during the breeding season. As you might imagine, with their short wings the thick-billed murres didn’t travel nearly as far as the kittiwakes during the winter. However the geolocation loggers that we used for them also had a depth sensor and over the winter we had birds dive to 200m, which is equally as impressive.