I went out and did a seawatch this morning and got almost
all the way through the hour without seeing anything unusual.

At about 10:10hr a a shearwater flew by at about 250m out.
My first impression was, "oh, Buller's Shearwater, cool."
It was the size of a Sooty (or a bit smaller) did more
flapping then gliding, low over the water and had a well
defined "W" shape from above. The back was gray, the greater
and median coverts were very dark gray and the secondaries
except for the tips were silvery white and very flashy.
The primaries were dark.

Then the bird banked. It was not light bellied. The underwing
looked very similar to the underwing of a Sooty, but had a distinct
dark break at the wrist. The belly was uniformly gray, about the
same color as the mantle. Throat was gray, though paler then
the belly. The bill was dark. The tail seemed wedge shaped.

Is there a dark morph Buller's? If not, any other speculation?

http://home.pacifier.com/~mpatters/obrc/shear_sp.jpg
--
Mike Patterson Alas, to wear the mantle of Galileo,
Astoria, OR it is not enough to be persecuted
celata at pacifier.com by an unkind establishment,
you must also be right.
---Robert Park
http://www.pacifier.com/~mpatters/bird/bird.html