Is the poop coming from birds perched on the vine or directly from nesting activity? Perhaps it would be feasible to suspend some replaceable cloth to catch the poop.

I don't think there is any birds nesting at this time of year? They have just come back each Spring. This is just the first time we've had a build up of poop. I really don't want something visible hanging there to catch the poop... I was thinking of the chicken wire as a deterrent. ? I'm wondering why now there is poop when there wasn't before. I haven't noticed an increase in birds- it's just weird.

Since the wisteria is a huge and powerful vine unless kept diligently pruned to remain unnaturally small maybe having it wrapped around the post etc. is not going to work out anyway - and the plant should be removed.

This would of course also take away the place for the birds to hang out.

There are tall native conifers in this region with wisteria vines growing all the way to their tops. In time the trunks of full-sized wisteria vines become quite stout. I have also seen a big one sending out runners across the top of a bed, like a sheet of piano wire. Not really a plant for a small space in a modest setting.