Today's pelagic didn't turn up any review list birds, but we did eventually run into a jaeger that Tim spotted on the water. We slowly worked up to it and it made a couple passes around the boat.
The easiest ID feature is the medium length pointed central tail feather; we get probably 5-10x as many juvies as adults at Tiscornia, it almost feels like cheating to get a close adult.
The marbled face, breast, and belly pattern are winter features.
The clean brown underwing marks it as an adult; per the Olsen and Larsson Jaeger book 2- and 3-year-old birds will retain at least some juvie feathers.