Kelly & Tweeters,

According to an article entitled "Caspian Tern Research on the Lower Columbia River," 388 tern nests were built on the barge anchored in Commencement Bay, but the barge was removed before the eggs hatched.
There was a discussion of this on Tweeters in 2001.
I also found an article on the feasibility of using barges as tern nesting habit.
There is an article archived by JSTOR, available through college and university libraries that subscribe to it, called Diet of Caspian Terns in Commencement Bay.
Links:
http://www.columbiabirdresearch.org/Season_Summary_2001/01SeasonSummary.pdf
http://mailman2.u.washington.edu/pipermail/tweeters/2001-June/016249.html
http://oregonstate.edu/robylab/pdfs/Collis_et_al_2002b.pdf
http://www.jstor.org/pss/1522274

Sandy Daniels, Enumclaw Plateau
Ladyhawk707 AT msn DOT com