I photographed this Pied-billed Grebe on 4-7 in NE Ohio. It was swimming near some coots and buffleheads but no other grebes that I could see when it would stretch its wings out and hold them in this position for a short while then slowly pull them back in. The grebe is in breeding plumage but the behavior looks like more of a threat display than courtship, or was it something else?
At this time of year, it may just be exercise in preparation for migration. Masses of scoters winter near the mouth of the Delaware Bay between New Jersey and Delaware. They move around a bit Dec-Feb, but come March you can see them picking up in large groups and flying in large circles. Kind of like people tuning up at the gym at the end of winter to get ready for outdoor activities. I guess even waterfowl have a "bathing suit season."
Jim, one other thing about this bird that makes me think it's tuning up is the condition of the plumage. If you look at the wings near the body, there are nice fresh feathers. If you start to move out the wing, there are big patches of dull brown old feathers. Go further yet and the alulas (those 3 longer feathers at the bend of the wing) look new. The coverts sticking up behind the older feathers look new too. I don't know how grebes molt but if this bird has recently molted in its new flight feathers, it might have been flightless not that long ago which would explain the need to exercise.
Thanks Paul and John for the info, it never occured to me that it may be exercising. It did do some wing flaps also, so yeah, probably just a strech but the length of time it held them and the way they're tilted forward made me think it was displaying.