Top left and right: Semipalmated sandpiper, Lower left: Spotted sandpiper, Lower right: White-rumped sandpiper. The photos were all taken on the same day at Totman Cove.
"Peeps" is birding slang for any of a number of North American sandpipers. Their vocalizations are numerous versions of the sound, "peep peep peep." Even though it's only the first week of August, they are beginning to congregate for migration, so there are a lot more of them around these days. The youngsters accompany their parents, adding to the numbers and also the difficulty of identifying them. The plumage of the newbies is not as distinct as they will be next year. They also move really fast on the ground and in flight, so it's hard to get a good look, unless you can get a photograph. And as we know, that presents its own challenges. They can be seen singly, as in the case of the Solitary Sandpiper pictured below, or in large groups skimming the water surface in wheeling arcs. Peeps and plovers, at the end of summer, separate the men from the boys (as my father would have said) in the world of birding identifications. 
These two photos of Semipalmated sandpipers were taken within a second of one another as the birds turned en masse against the sunlight, making them look like completely different birds. I was whizzing along in our small boat when they whizzed by me even faster. I nearly broke my neck and fell out of the boat trying to turn fast enough to photograph them. My husband, the helmsman says he would like advance notice when I intend to spin in my seat like that, lest I tip us over. Imagine that. In my efforts to be sure about identifications, before opening my mouth or zipping the keyboard beneath my fingers, I have spent way too much time beating myself up plowing through bird books. Ultimately, I'm probably wrong anyway. If I have mis-identified any of these, I'm sure my loyal readership will let me know. It's a lot more fun racing around in a tin boat with a boyfriend than it is looking through field guides anyway. I'll leave the academics of birding to those with less imagination than I have.
This is a Spotted sandpiper beautifully camouflaged against the rocks. I've only seen them one at a time and always like this scurrying across the rocks.
Solitary Sandpipers don't hang out with other sandpipers. I only see one or two a year. When I took this shot, I thought I was photographing another Spotted Sandpiper, which I had just seen moments before. It wasn't until I developed the photo that I realized they were not one in the same.