You can hang CDs or other shiny things. There is even shiny tape marketed as a bird deterrent. There are also bird of prey decals you can stick in windows that might deter smaller birds.
If there doing flybys there is nothing you can do. If there is a roosting area in which they sit, you need to make this less attractive to them. The ideas that Steve mentioned works, but for larger flat areas bird spikes that can be purchased at some home centers can be glued to the flat areas making it impossible for them to land.
Some people hang blank CD disks to scare away creatures...they are shiny and move freely in the wind. You can chose something more attractive and try that.
Thank you for the suggestions but this doesn't answer my question because the column is near the front door so I can't hang cd's. It is also not a nesting area. I am not even sure how they can land as there is no flat surface, just a vertical column. The problem area is facing the house partially under the porch so they aren't just flying by. Any other suggestions would be greatly appreciated.
is there any way you can take a photo of the offending column and porch area? There is really only two ways this is happening. Roosting on something above or flying by. How bad is it?
I was bothered by this same problem. I kept getting a mess on my front porch. One day I was out there and a little bird simply flew over to the brick arch and landed on a vertical surface...their feet have claws that allows them to sit anywhere! I learned then that all I could do was continue to clean up the mess. I pour warm water over the spots, give it a few minutes to soften and then rub it with a paper towel under my foot! I don't know if WD40 will hurt your posts or not but it would make their traction not as easy! Sometimes there just is no solution.
Just ask them to stop, lol...that works as well as anything.