I'm not sure about ebird-specific requirements requiring a separate list
for seabirds.
But you might find this article about the top "yard lists" interesting :
https://www.birdwatchingdaily.com/beginners/bird-friendly-yards/a-yard-like-no-other/
It features both Paul Lehman's home at Cape May (316 species), and Jim
Stevenson's list in Galveston (318). I've seen photos of Paul on the roof
of his home with massive optics, no doubt picking up seabirds for his yard
list.
The article specifically mentions seabirds and raptors being included.
