[Tweeters] How do Cassin's Auklets work?

[Pearson, Scott F (DFW) via Tweeters]

All,

The Islands off the Washington Coast are all managed by the USFWS Washington Maritime National Wildlife Refuge Complex.  The only coastal seabird breeding rocks/islands not managed by the Refuge belong to the Makah Tribe (Tatoosh and associated rocks) and Destruction Island (still under USCG management).  Public access is restricted to all of these islands to reduce impacts to breeding birds and because they are extremely difficult to access and are extremely fragile (native vegetation and potential for erosion).

Cassin's breed in burrows on a number of our offshore rocks and islands.  For example, Alexander is riddled with Cassin's burrows but this Island also has many Fork-tailed Storm Petrel, Leach's Storm-petrel, Tufted Puffin, and Rhinoceros Auklet burrows along its upper slopes.  The native vegetation is mostly intact on Alexander due to the lack of human visitation.  Whereas islands like Destruction and Tatoosh, both of which have had considerable human activity post-contact (they both have lighthouses), has a lot of non-native vegetation and even non-native species like the European hare on Destruction that has caused considerable erosion and loss of seabird nesting habitat.  In the short time that I have been going to Destruction (almost annually since 2007), I have seen portions of the slopes slide into the ocean that supported dozens of Puffin burrows.  It is clear to us that the rabbits are responsible for much of the erosion.

If inexperienced people were to start visiting these islands (like kayakers), they would likely introduce non-native vegetation that could make the islands unsuitable to burrow nesting seabirds and they would likely collapse many burrows with adults, eggs, and/or chicks inside.  I have spent the past couple of decades working on seabird colonies and I still feel very uncomfortable with any human activity (including my own) on these islands.  To minimize impact and to gain information on population trends, we (USFWS and WDFW) have been placing acoustic monitoring devices on islands like Destruction, Carol, Alexander, Jagged, and the Bodeltehs.  These devices allow us to track vocalization rates over time as an index of abundance and to assess trends.  We are also attempting to compare calling rate with burrow density.

As Bob pointed out, these birds return to their colonies after dark.  Based on our acoustic monitoring of Alexander for example, Cassin's don't return to the colony until about 3 hours after sunset and leave the island a good hour or two before sunrise.  The best place to see these birds is on pelagic trips.  When we are surveying the offshore environment, we tend to start to encounter Cassin's just before the shelf-break.  Unfortunately for us (and maybe Cassin's) our shelf-break is relatively far offshore than in some areas off Oregon and California.  But, I have also seen on Cassin's in Port Townsend Bay - like all species, you can see them out of range especially after storms.  For maps of the offshore distribution of some of our seabirds, check out the following:

https://repository.library.noaa.gov/view/noaa/9329

https://espis.boem.gov/final%20reports/BOEM_2021-014.pdf

Good luck!


Scott


Scott Pearson, PhD
Senior Research Scientist
Wildlife Science Division
Washington Department of Fish and Wildlife
1111 Washington St. SE
Olympia, WA  98501
360-584-2107

he/him/his

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