the Adventures of Nicki and Ricky: Mystery Shell Tree in Bloomington, MN

While exploring the strip of beach behind their house, siblings Nicki and Ricky find a tree surrounded by broken shells. A perfect mystery for Detective Ricky and his sidekick (errr, partner) Nicki! Looking closer, they discover broken shells in the tree's branches as well as piled on the ground.
But how... and why... did they get up there?
It's a MYSTERY!
Don't speculate... it's time to INVESTIGATE!