Tweets,
As mentioned by Bruce we had a great day at sea today. The link below will take you to my photos of "The" petrel. I managed exactly 30 pics of which 15 were of perfectly focused waves. The 10 I have posted are the best of what's left. None has been modified except for cropping. I have made no contrast, luminance, temperature, or sharpening edits, just cropping.
Looking through Onley and Scofield (2007) the light smudge on the flank at the back of the wing, the relative lack of contrast between the "M" on the wing coverts and the back/rump, and the cap being darker around the eyes than on the nape started to make me nervous (that is, I became less convinced of Hawaiian). However, everything I have found on the net contradicts Onley and Scofield on the importance of those characteristics. Considering what I have found on the web, today's bird lacks any dark smudging in its axillaries (seen consistently in varying degrees of every photo, and drawing I have found of "Dark-rumped" Petrel taken/made near the Galapagos Islands, and its tail is shorter than the same Galapagos birds. Today's bird's plumage seems consistent with the birds seen of California, which to my understanding have all been called Hawaiian.
Hawaiian has my unprofessional vote for what it is worth.

Link to my photos from today:
http://www.pbase.com/hoodedcrow/hawaiianpetrel

Links to the more useful sites I visited:
http://montereybay.com/creagrus/DRPE_id.html
http://fog.ccsf.cc.ca.us/~jmorlan/drpe081306.htm

List of resources consulted (with varying degrees of usefulness) from my personal library.
Seabirds; Harrison (1983)
Seabirds of the World; Harrison (1987)
Albatrosses, Petrels, and Shearwaters; Onley & Scofield (2007)
I also checked out "dark-rumped" petrels in the 2008 Rare Birds Yearbook, The Birds of Hawaii and the Tropical Pacific, Birds of Peru, and Birds of South Asia The Ripley Guide (Barau's Petrel), but they don't really tell us anything the first three don't.

Good Birding,
Matt Pike
Lacey WA
hoodedcrow3b at yahoo.com