Sound Science: Where do puffins go in the winter?

New tracking technology sheds light on seabird migration

Researchers at Prince William Sound Science Center have just begun to scratch the surface of their first year of data tracking adult Tufted Puffins in the Gulf of Alaska during winter. Some of these results are challenging conventional knowledge about the species. Starting in July 2018, research ecologists, Kristen Gorman, Mary Anne Bishop and Anne Schaefer set out to track Tufted Puffins during the over-winter period by deploying geolocator, or GLS, tags on adults nesting at Middleton Island in the Gulf of Alaska.

The goal of the study is to fill knowledge gaps in Tufted Puffin ecology during the non-breeding season — specifically aiming to reveal where the puffins winter in the Gulf of Alaska. Puffins have never been seen in abundance during historical winter seabird research surveys, so Kristen and Mary Anne hypothesized that puffins migrated away from the coast to waters in the central North Pacific where they were unlikely to be seen.

Researchers used a “burrow scope,” a tube with a miniature infrared camera on the end, to see if the banded puffins were in their burrows. The use of this technology allowed the scientists to be less disruptive to the puffins, who are known to be sensitive to disturbance during the breeding season.

Kristen and Mary Anne’s interest in exploring puffin movement coincided with both a growing concern for Alaska’s Tufted Puffin populations, along with advancements in tracking technology that allow scientists to attach extremely lightweight GLS tags to leg bands that can be safely deployed on seabirds.

During their first summer of field work on Middleton Island in 2018, Kristen and Anne successfully outfitted 30 adult breeding puffins with GLS tags. These tags are archival, meaning that the data are stored directly on the tag. While data archiving allows for the tags to use less battery power, resulting in lighter-weight tags, data archiving also requires that the tags be physically retrieved to download the data. Thus, Kristen and Anne returned to Middleton Island in June of 2019 to retrieve the 30 GLS tags deployed in 2018.

Puffins typically return to the same nesting burrow each year. Burrows are typically excavated by the birds into soft soils along a hillside that allow them to take off readily to forage as puffins are not incredibly agile fliers. Ideally, the researchers expected to find the same puffin they had tagged the year before back in their burrow raising another chick, which allows for tag retrieval. Amazingly, Kristen, Mary Anne and Anne had great success in 2019 retrieving GLS tags. Of the 30 burrows that had been occupied by tagged adults in 2018, 29 burrows were active with an egg present and many burrows were attended by an incubating parent.

By the end of the 2019 field trip, the team was able to retrieve 16 GLS tags, considered by Kristen to be a great success. Puffins dive to forage in the water and the researchers were concerned about what the impacts of the diving would be on the tags. Would the tag’s plastic casing survive? Did the tag operate properly, and would the data be accessible?

Fortunately, the data from 15 of 16 GLS tags were perfect, complete with 11 months of light level information to discern location (latitude and longitude), wet/dry cycle and sea surface temperature information. Only one tag had a battery that failed halfway through the year, resulting in a partial dataset. Of the tags that were not retrieved, Kristen is hopeful they will find these during the field season in 2020. For the birds that did return with tags in 2019, Kristen and Anne removed the plastic band holding the geolocator and took body condition measurements, as well as feather and blood samples for stable isotope analysis. The team banded an additional 30 puffins with GLS tags in 2019, which will be retrieved in 2020.

Researchers were thrilled that the GLS tags did not cause any harm to the legs of the puffins, and that the geolocators had not been damaged by the cold saltwater.

Data analysis for this project is no small feat. Each of the 16 geolocator tags have tens of thousands of lines of data. Light level measurements can be processed with a series of algorithms to determine latitude and longitude, which are associated with a timestamp for a record of the puffin’s movement. This information can tell us how puffins are using different habitats in the ocean relative to season and aspects of the annual cycle such as molting.

In the early fall, puffins undergo their primary molt, losing all their flight feathers for a period of time. This molt is a critical part of the non-breeding season for puffins as they need to be able to find food in their immediate vicinity. If the birds are spending a disproportionate amount of time in one area in the fall, it is likely where they are going through their molt.

Although the researchers have not yet had time to process the data to this extent, they have compiled all the overwinter data together to get an idea of the general areas the puffins are using. From preliminary analysis, it appears that the puffins are restricted to the Northern Gulf of Alaska, contrary to the distribution into the central North Pacific they had expected. From Middleton Island east to Southeast Alaska, the puffins stayed much closer to the coast than expected.

“The big thing here is their ability to find food,” Kristen says. “What will be interesting is to see how variable the tracts are between years. It might give us a sense of whether there are consistent regions of the ocean that are entraining food for the puffins.”

Another aspect of the study aims to compare the movement data from GLS tags with oceanographic variables and body condition data. When analyzing the stable isotope signatures of the initially tagged birds, Kristen found that the isotope data predicted the body condition of adult females. Kristen suspects that these different isotope signatures, which signify feeding on different levels of the food chain, will be related to different foraging locations. It will be interesting to see where individuals are spending their time relative to isotope signatures and body condition as an enhanced body condition can set them up for a successful breeding season.

Over the next few years Mary Anne, Kristen and Anne will focus on analyzing the data obtained by the geolocator tags. By sharing insight into the currently unknown movement ecology of Tufted Puffins, conservation steps can be taken to ensure their survival in the years ahead.