Bird Sighting on the Shenandoah

I went bird watching this afternoon along the Shenandoah River. A dank, dark and dreary day. The light filtering through the monotonous cloud cover was flat and made everything else look rather flat too. The river was slate grey lacking any blue or green to reflect. Wild life was few and far between but I did make a few sightings and practiced identification.
I used my car as a blind, pulled off whenever I saw motion on the water, and rolled down my window to use my field glasses. This worked well, as the birds seemed to feel totally unthreatened. I saw many groups of Canada Geese waddling along the shore, upending in the water, or standing motionless on the flat rocky areas midriver. I also saw two species of diving ducks.
Two pairs of Hooded Mergansers were feeding out in the middle of a wide expanse of the river. Each duck completely submerged beneath the water when it dove, but one drake was always left alert and watching, like the periscope on a submarine. The Hooded Merganser drake has striking black and white bars on his wings and shoulders. He has a sail shaped white crest flaring back from his black head. The crest can be that can be raised or lowered which was startling and confusing as I tried to make out the "shape" of the birds head--it kept changing! This was the most exciting find as these birds are "fairly common" as opposed to "common."
At one spot protected from the wind by high banks, several species were congregating in leisurely groups where a cluster of flat rocks formed an ersatz archipelago. Five or six pairs of Common Mergansers appeared to doze with their bills turned back and hidden under their wings, while other pairs paddled calmly back and forth nearby. Mingled in were the everpresent geese, and mallards. Mallards are "dabbling" ducks per Peterson, so now I have the word for their bobbing pattern of feeding, they quickly upend to snap a morsel than right themselves like a rubby ducky in a bathtub. I have seen them diving too when a tidbit is out of reach.
I saw one little shore bird skittering along nearby--It was pale colored and seemed to have 3 dark rings around its neck, but the most similar looking bird in My Peterson Guide of Eastern and Central North America had two rings: a Kildeer?
I tried to interpet the behavior of three crows that flew down to the rocks after surveying the scene from a nearby tree. They appeared to be honing their beaks on the rocks, or perhaps attempting to scrape some substance off of them? One crow would be "honing" while the other two kept watch in different directions. A small mess of starlings fussed around this scene as well, flying up to perch in the trees, then soaring across the rocks, alighting briefly, then back up again. The Mergansers, although "common" were very beautiful. The males had immaculate white breasts and flanks, glossy black-green heads and bright red bills and feet. The females had ruddy brown feathery crests that I found in very good taste with their dress of muted grey.

This site has a great photo of the Hooded Merganser and you can listen to its call. Sounds like a frog, very strange! http://www.ducks.org/hunting/waterfowlGallery/61/index.html
Here is some interesting information about the Common Merganser. They are the first duck to move north in the spring and the last to go south in the fall...
http://www.seaduckjv.org/infoseries/come_sppfactsheet.pdf