The booby this morning at La Jolla Cove was a near adult, somewhere in late 2nd-cycle.
It showed, as Dan Jehl described, basically all white plumage on body and wings except for the black remiges, some brown speckling to the upperwing coverts and back, and a brownish head.
Howell and Zufelt’s new Oceanic Birds book says [pp. 306-07] that 2nd-cycle Nazca boobies show a brown shawl to the crown and nape, whereas Masked boobies at that age show a white head and neck.
So even not having seen the bill very well [although I thought it was orangey at the base], this field mark of the brown crown and nape on an otherwise near-adult bird, if correct, would identify the bird as a Nazca.
As Dan mentioned, it was very similar in plumage to the bird seen at Dana Point until a week or so ago.
Also, it was no more than 200 yards offshore, heading south in a direct fashion.
Stan Walens, San Diego
August 24, 2019; 3:10 pm