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Seabird Telemetry 2008

Bering Sea Project Seabird Telemetry crews have been tracking black-legged kittiwakes that are raising young on St. Paul and St. George islands to learn more about their foraging patterns offshore.

A challenging year

kittiwake tracks2008 was a year of comparatively low nesting success for kittiwakes on both islands -- apparently due to low food availability -- but fortunately kittiwake nests did not completely fail on either island.

Researchers noted that St. George kittiwakes did NOT seem focused on foraging over the shelf break or over the Pribilof Canyon, contrary to expectations. Instead, most foraging trips were long distance and involved directed flight far beyond the shelf break to foraging areas in deep water.

One St. George kittiwake even flew all the way to Bogoslof Island, despite raising a chick on St. George! To a lesser extent, St. George kittiwakes also foraged over the shelf using circuitous, searching flight, and nearshore over the island’s shallow kelp beds.

Above: At-sea GPS tracks of chick-rearing Black-legged Kittiwakes at St. Paul (N=18) and St. George Islands (N = 18) during July 2008. (Bathymetry map: dark grey: 5-100 m, light grey 105-200 m). See larger image

Different island, different strategy

St. Paul kittiwakes apparently favored a different foraging strategy. While a few of the St. Paul foraging trips were long distance flights beyond the shelf break, the majority were over the shallow waters near St. Paul. Like the St. George kittiwakes, some St. Paul kittiwakes foraged over the shelf using the same circuitous, searching flight, the type of foraging trip that we expected would prevail for St. Paul kittiwakes.

So although St. Paul and St. George kittiwakes displayed a similar range of foraging strategies, the focus for St. George kittiwakes was the deep waters to the southwest, while the focus for St. Paul kittiwakes was the nearshore. Amazingly, there was no overlap in the foraging tracks of kittiwakes from the two islands, suggesting that neither group was targeting foraging hotspots.

What does this mean?

We don’t know yet whether these foraging patterns and the differences in kittiwake foraging patterns between St. George and St. Paul are typical or reflect the scarcity of food for kittiwakes raising young in 2008. Continued study in 2009 and 2010 should help resolve this uncertainty.

Kudos for the field crews

The two Seabird Telemetry crews -- Rosana Paredes, Nathan Banfield, and Caroline Poli on St. George Island, ably assisted by Ann Harding; and Rachael Orben, Ana Santos, and John Warzybok on St. Paul Island, ably assisted by Alexis Will -- have done an absolutely fabulous job of collecting these data. They have frequently had to work under adverse conditions with temperamental new technology, but they were always determined to overcome the obstacles and collect these completely novel foraging tracks.

They collectively deserve all the credit for the success of this first field season, especially the two crew leaders: Rosana Paredes and Rachael Orben. Without these "dream teams" in the field, there would have been little to show for this first field season, which happened to be a year of low food availability and mediocre nesting success for both kittiwakes and murres on the Pribilof Islands.

Read more about Summer 2008 fieldwork in the Pribilofs and on Bogoslof Island