Dear etaoin: sorry about that. I didn't realize it was so limited. His CD is quite good, and with it I think goes access to some of his online stuff, but I haven't tried it.
I was hoping someone might know why rooks' range seems so limited. I remember the bill is different, which may limit their choice of nutriments. But why should they be common in UK, but not in MA?

Here's a site from Wales,UK, with a picture, showing whitish patch at base of bill, which should make them easy to tell from crows, if North American ones are like this.
http://www.fishing-in-wales.com/wildlife/birds/rook.htm