Strung Out

Had such good luck last Sunday by the rocks at Fort Fisher, we made another visit today. Tide was going out, so less wave action and no surfers. Saw these birds last week, very close to shore, but couldn't adjust from my slow, water smearing shutter speed in time to capture them. This time, there were many more of them but off at a distance. They seem to follow along in single file, swooping and curving like a long kite tail. Anyone know what kind they are?

If you look closely you can see another string close to the left edge right at the water line.

This should definitely be Viewed Large