Researchers must work hard to study the Cassin’s Auklet in its habitat. Due to its secretive nature and because it is a seabird, its preferred environment is far out to sea and on small unpopulated islands free from introduced mammalian predators. To study its breeding habits calls for an even heartier scientist, for this auklet visits its colony only at night, and its days are spent out to sea, foraging for its young. The Cassin’s Auklet is a member of the alcid family, a group of diving seabirds that include the well known puffins. Its shape has been described as similar to a small nerf football!

These slate-grey colored fast-flyers are able to forage over great distances to feed their young, as USGS researchers at the Western Ecological Research Center found out in a recent study at California’s Channel Islands. But exactly how far out to sea will nesting auklets go in order to forage for “seafood” for the single chick in their nest? For three successive years, over the three months during each springs breeding season, the researchers worked diligently to survey the Cassin’s Auklets foraging behavior.

Researchers Josh Adams, John Takekawa, and Harry Carter undertook their study beginning in 1999. The study “used radio telemetry to measure foraging distances and individual home-range areas among individual auklets from two colonies in the northern Channel Islands, California.”

In order to accomplish their research, the scientists needed to radio tag a number of breeding auklets. They were able to successfully capture, tag, and record data from a total of 99 birds. Important to their successful work: ATS Avian Transmitters, Model A2100. Using these transmitters, the scientists could verify the presence or absence of the Cassin’s Auklet when they are most difficult to locate – at night. In fact, in order to capture and radio tag the seabirds, the researchers worked though the night; this is the only time the birds visit their brooding grounds, dug into burrows or nestled within a rocky crevice, where they attend to their chick and catch up with their mate for the night.

Having completed tagging, the research could begin. Two methods of tracking were used: aerial and fixed unattended stations. Aerial tracking techniques were used to locate far ranging auklets during the day as they foraged far out to sea. A total of 116 tracking flights were flown in either Cessna or Partenavia aircraft in order to complete the study. Two wing-mounted directional yagi antennas were connected to an ATS two-way antenna switchbox, whose output was routed to an ATS Model R4000 Scientific Receiver on-board the aircraft.

At night, the researchers were able to determine presence or absence of the birds once they had returned to their nesting colonies. This was accomplished through the use of multiple fixed unattended monitoring sites, where ATS Model R4000 Scientific Receivers were connected to ATS Model D5041 Dataloggers. Two different antenna set-ups were employed. One used dual H-type antennas, the other, an omni-directional dipole antenna. This type of monitoring site allows for extended periods of automatic, unmanned transmitter monitoring and attendant data acquisition.

According to the author’s published paper, this important study is unique in being the first “extended observation of the distribution and movements of Cassin’s Auklets through their provisioning period.” For these far reaching birds, the scientists even considered pelagic wind data that had been observed and recorded by the National Data Buoy Center over many years (it turns out the prevailing winds made little difference in the distances the birds flew). After considerable analysis, the researchers determined that these populations of auklets had flown an average of 38 km from their nesting habitat, which consists of a burrow around one foot deep, beneath dirt and brush. Data from their study also indicated that a few of the trips taken by the birds were upwards of 95 km from their nest.

Past research had found that Cassin’s Auklets average 45 km/hour in flight, and spend about 17 hours per day out to sea. Therefore, the researchers determined, “an auklet flying 10% of the time would have a maximum foraging radius of 38 km, very close to the average maximum foraging distance that we determined for auklets (30-37 km).”

In a complementary study Adams et al. analyzed the food brought back by parents to feed their chicks; observations indicates that these auklets feed on the same prey as blue whales, salmon, and basking sharks: krill. The auklets use their wings for propulsion in order to swim under the sea in search of food. Dives are about 1 minute long and birds may reach depths >30 meters.

As recently as the early 1990’s, most research work designed to calculate foraging distances of alcids have used cursory time/speed/distance calculations based on observations at the colony, or has required use of ships for direct observation of birds at sea. However today, similar research utilizes modern radio telemetry equipment and techniques. This has helped make the researchers work more efficient, and more economical, while still allowing for direct observation of the species. Right now, birds of all species are in-flight the world over, and some of them, like Cassin’s Auklet, are being continually tracked and observed by scientists, many times with the help of ATS transmitters, receivers, and antenna systems.

Adams, J., Takekawa, J.Y., and Carter, H.R.. 2004. Foraging Distance and Home Range of Cassin’s Auklets Nesting at Two Colonies in the California Channel Islands. The Condor 106:618-637.

Adams, J., Takekawa, J.Y., and Carter, H.R.. 2004. Stable foraging areas and variable chick diet in Cassin’s auklets (Ptychoramphus aleuticus) off southern California. Canadian Journal of Zoology 82:1578-1595.