This is the video of the Fish Crow that I recorded from Fort Erie, Ontario on January 15, 2012. You'll need to turn the volume up as it is a fairly quiet video with a bit of background noise. Feel free to leave comments on what you think.
0:01: You hear me go "shh", right when an American Crow calls.
0:02: The Fish Crow calls (very short, nasally single note)
0:03 - 0:06: An American Crow calls several times
0:10: The Fish Crow does the same nasal note, and you hear me say "It just called again" right after.
0:13: The Fish Crow calls immediately once I finished saying "It just called again"
0:18: The Fish Crow calls a final time.
Throughout the duration of the observation, we only heard the single nasal call note from the Fish Crow, and we didn't hear the double "uh-oh" note that they also do. It responded to the playback I played on my phone which was the first vocalization that is given for the app "IBird Explorer Pro 2". Its call sounded identical to this recording. It called between 5-10 times after I played the call note on my phone several times. After that, the bird was silent until I prompted it by re-playing the call on my phone. It continued like this until the bird flew across the river with the rest of the American Crows. While we most likely saw the bird, we couldn't pick it out from the other American Crows. I never got a really good look at any of the crows in the tree.
After that observation we spent the next half hour watching and listening to the thousands of American Crows swarming by. Many landed in trees for several minutes before continuing. None of the other crows made the Fish Crow-like nasal "cah", despite many attempts with playback on my phone.
I don't have any video editing software so the video is pretty rough. If someone is able to edit the video to clean up some of the background noise/make the crow calls louder, let me know and I'll send you the file.