For more information on species & ecosystem science:

Wildlife Science

Fish Science

Habitat Science


Lead Scientist: Scott Pearson

Ecoregions: Puget Trough, Northwest Coast

Ecological Systems: North Pacific Maritime Coastal Sand Dune and Strand, North Pacific Coastal Cliffs and Bluffs


Photo by Peter Hodum

Rhinoceros Auklet with a bill load of sandlance on Protection Island

Click on photo to enlarge
Photo by Peter Hodum

Volunteer researchers Nathalie Hamel from the University of Washington and Lucho Alva from IMARPE in Peru help with fish measurements


Photo by Peter Hodum

Rhinoceros auklet burrows on Protection Island


Photo by Peter Hodum

Undergraduate University of Puget Sound student, Emma Kelsey is wearing a visor and holding a cable of an infra-red camera probe used to assess auklet burrow occupancy and reproductive success. Emma received a University Scholarship to assist with this project.


Diet composition (% by weight for each primary species) in the diet of rhinoceros auklet chicks on Protection and Tatoosh islands in 2006 and 2007.


Seabird Ecology

Rhinoceros Auklet Ecology

Project Description

Evidence suggests that bird populations in the Salish Sea (Puget Sound, Strait of Juan de Fuca and Strait of Gerogia) are declining. The mechanisms responsible for these apparent declines have not been identified. Unlike many species of seabirds that use the Salish Sea during migration or for over-wintering, rhinoceros auklets (Cerorhinca monocerata) depend on this region for reproduction. As a result, population trends are more likely to be tied to events occurring locally. In addition, as a top-level piscivorous predator, the species is particularly susceptible to fluctuations in forage fish populations. These characteristics make the rhinoceros auklet an ideal candidate for assessing the health of the Salish Sea ecosystem. An additional advantage to using this species is the availability of historic data from the 1970s for assessing population trends.

To assess whether or not Salish Sea marine birds, and rhinoceros auklets in particular, are diet limited, we are comparing reproductive success and chick diet of rhinoceros auklets nesting on Protection Island in the eastern Strait of Juan de Fuca (2006-2009), on Tatoosh Island on the western end of the Strait (2005-2009), and on Destruction Island on Washington's outer coast (2008-2009). To put our data in an historic context, we compared our data to similar data gathered in the 1970s. In addition to examining potential mechanisms for seabird declines, this Sound-coast comparison helps us determine if events unique to the Sound are driving the declines or if declines are part of events occurring at much larger spatial scales.

Greater than 95% of the North American population of the rhinoceros auklet occurs in Washington, British Columbia, and southeast Alaska. Nearly all of these birds breed on eight large colonies, of which Protection Island in Washington is one of the largest. The importance of this island to the species as a whole inspired us to assess changes in its population using a stratified random sampling scheme.

This work was funded by the SeaDoc Society, U.S. Fish and Wildlife Service and Washington Department of Fish and Wildlife.

Key Findings

  • Preliminary results suggest that diet quality (calories Preliminary results indicate that burrow occupancy was extremely high on the coast and in the Salish Sea in 2006 (~80%) but dropped somewhat in 2007 (Protection = 65%, Tatoosh = 76%).
  • Preliminary results indicate no difference in hatching or fledging success between islands or between the 1970s and 2006-2008.
  • On the coast, burrow occupancy was quite low during the anomalous 2005 season, when it dropped to only ~50% on Tatoosh, suggesting that climate forcing can have a significant impact.
  • In the Salish Sea, sandlance and to a lesser degree herring made up the majority of the diet. On the coast, Rhinos brought back a different and more diverse diet.
  • Bill load size did not differ among islands or years suggesting that this metric is not sensitive to changes in marine conditions. In 2006 and 2008, Birds foraging on the coast (Destruction) or birds with the option to forage in the Salish Sea or coast (Tatoosh) returned with fewer - larger fish with significantly higher energy content (KJ/g). There were no differences in energy content per bill load between the Salish Sea and coast in 2007. This lack of difference was driven, in part, by an increase in larger, energy rich herring in the Salish Sea in 2007 and a concomitant decrease in sandlance.
  • Diet composition on the coast appears to vary significantly among years but varies to a much lesser degree in the Salish Sea. Preliminary results indicate lower food quality in the Salish Sea. In addition, it appears that diet quality and composition are particularly sensitive to changes in the marine environment.
  • In 2008, we estimated that there are 54,113 ± 9,390 (95% CI) burrows on Protection Island. This estimate is approximately 51% greater than previous estimates. Using infra-red camera probes to assess burrow occupancy, we estimated occupancy to be 66% ± 5% (95%CI) which is very similar to previous occupancy estimates. Using these two values, we estimate that there were 71,430 ± 13,514 (95%CI) birds breeding on the island in 2008. These results make Protection Island the third largest rhinoceros auklet nesting colony in North America. The concentration of such a large portion of the North American rhinoceros auklet population on Protection Island suggests that population trends and success on this island has significant implications to the species.

What's New

  • We are currently analyzing our 3-island diet quality, diet composition and reproductive success information with the goal of producing a manuscript for submission to a journal in the spring of 2010.
  • In 2009 we completed our field work for an island-wide estimate of burrows and occupied burrows on Destruction Island and will report our results in the late winter of 2010.
  • In 2010, we will conduct similar burrow count estimates for Smith Island and work on producing a manuscript explaining our methods and presenting the 3-island burrow estimates and the rhinoceros auklet habitat associations.  Identifying habitat associations provides critical information needed for maintaining and restoring auklet habitat.   
  • These burrow and population estimates can be repeated in the future to provide colony trends.