In the past I have been asked what a wrack line is by friends when I have mentioned it while talking about my shorebird photography. A wrack line is an area on the shore just above mean high tide where wave action can deposit driftwood, seaweed, manmade items, eelgrass, the remains of marine creatures and small invertebrates and can be a prime feeding ground for birds and animals that are hunting for food.
I photographed this Short-billed Dowitcher and the out of focus Sanderling the day after a storm had pushed mounds of Sargassum seaweed onto the wrack line and the birds were busy looking for food within it. This Dowitcher gave me a nice wing stretch before it moved further down the beach.
A word of warning; if the wrack line does have the remains of marine creatures in it you may have to hold your breath when near it because it can smell absolutely horrible.