This Pelagic Cormorant on the north side of the park appeared to be bathing. It was probably wetting its feathers in preparation for a day’s work diving for its meals. Cormorants don’t waterproof their feathers with preen oil the way ducks do. Wet feathers help them dive and swim underwater quickly and efficiently. See more about them at the Cornell bird lab website and the Audubon website. The Cornell coverage of the related Double-crested Cormorant talks about preen oil and wet feathers; it says
Cormorants have less preen oil than other birds, so their feathers can get soaked rather than shedding water like a duck’s. Though this sounds like a liability, this is thought to be an adaptation that helps cormorants hunt underwater more effectively.
The wet feather adaptation accounts for the familiar sight of cormorants standing on land and spreading their wings to dry in the wind and sun.