I thought about this again this morning. There is another possibility, it could be a Blue Jay. Our Blue Jays have about 7 different calls including one that sounds rather like someone hitting a 3" PVC pipe on the open end, Booonk Booonk. Something like that. Could that be your bird? I guess you'll just have to invite me out to do some birding and fishing with you!

All the best, and enjoy the birds!

Dave