Most of these oystercatchers are standing on one leg and sleeping with their beak tucked under their wing yet they have an eye open.  Apparently many birds sleep with one eye open and half of their brain awake. This is called unihemispheric slow-wave sleep (USWS) allowing birds to detect approaching predators while still getting a bit of rest so they are able to decide whether to keep one half of the brain awake or allow both halves of it to sleep. This enables them to spring into action quickly from rest if a threat approaches while still being able to satisfactorily sleep if no threat arises.  When migrating long distances where there are few chances for rest, birds can use USWS to both sleep and navigate at the same time. In the extra none of the oystercatchers seem to be asleep

Turnstones and gulls were joining them on the rocks and probably waiting for the tide to recede while nearby, male eider ducks were busy cooing and trying to attract females in the relatively calm water after the recent rough seas.