Buckthorn berries are different. They cluster, but around the stem.
http://www.ext.nodak.edu/extnews/newsrelease/2004/090904/07makesu.htm
If they're chokecherries, they are wonderful. They also make a good chokecherry wine... If you taste them straight though, you'll think ugh... Because they're really sour, and they'll make your mouth pucker.
Did you ever find out/verify if these were chokecherries?