In early March of 2001, I built two Gilbertson style Bluebird nest boxes made from 4 inch PVC plastic drain pipe and installed them on my Bluebird trail.  This was my first effort to make nest boxes from plastic which included some design changes from the Gilbertson original.

During one of my first nest-checks that spring, I found much to my despair, a pair of  Tree Swallows that had apparently starved to death in one of the 4" plastic nest boxes.  At that moment, I remembered reading years previously that a Bluebird nest box should never have an inside cavity dimension less than 4 1/2 inches.  According to the author, a dimension less than 4 1/2 inches would not provide enough space for the birds to open their wings and "flap-jump" to the entrance hole.  Even though my PVC nest boxes had grooves in the plastic for use as a "ladder" to climb out of the box, the swallows were apparently too crowded to escape from my "trap".  I was devastated and vowed to myself that I would never make another nest box from 4" PVC.

I was, however, still intrigued by the thought of making a round nest box.  Later that spring, I was working in my wood shop attempting to build a "stove pipe" style predator guard for the mast of my Purple Martin house.  I was making it from 6" PVC and had a 10' piece of the pipe laying on the floor.  I also was preparing natural gourds for use as nest structures for Purple Martins, and was cutting the threaded tops from one-gallon plastic bottles to be attached to the gourds as access ports to the gourd cavity.

While taking a break, I glanced at a piece of 6" PVC and a few 1-gallon plastic bottles which were laying side-by-side on the floor and noticed the similarity in their outside dimension.  As I picked up a section of PVC and one of the plastic bottles, I slipped the bottle into the pipe and realized how well the two pieces fit together..........I experienced a true epiphany and bells began to ring in my head.  Six inch PVC pipe would allow more space for the birds to exit the nest box unlike the 4 inch box with which I had experienced the Tree Swallow tragedy.   In a  matter of seconds, I developed a prototype nest box in my head that turned out to be what I now call, the Slippin' Silo, because of the way the round plastic bottle slips neatly into the round PVC pipe.

After that eventful night in the shop and having had my "first vision", there were many long hours of planning and design changes to perfect the model that is available today.  The early prototypes were designed to satisfy some of my own needs and desires in a Bluebird nest box.  I was never satisfied with any designs that I read about or built myself.  But after working with the silo design, I realized that it did everything I ever wanted a Bluebird nest box to do.  It also appeared to be satisfactory for smaller cavity nesting birds.  After placing a few silos on my Bluebird trail for field-testing, other bird enthusiasts saw them and wanted one of their own.  My own field-tests suggested that the silo idea worked well and proved that the neighborhood birds loved them. I made several more boxes for friends who had expressed an interest in owning their own Slippin' Silo so they could field-test them also.

At this point, the "word spread" about Worley's Slippin' Silo nest box.  Requests for silos began to come in from far and wide.  I soon realized that the little PVC nest box that I made for myself was highly desired by others, and so, I began to make and sell Slippin' Silos.  User feedback can be viewed by clicking here.