Birds perching onthe top of balustrades and guardrails can be a real nuisance.
At the very least you can get bird poop all over the place.
If there are parrots around I have known them to start chewing the wood.
Some of the solutions such as plastic spikes or non drying slimy paint aren’t always sutable solutions.
When I saw this solution at a house I visited I had to share it on this blog.
Basically 4 lengths of fishing line are stretched between staples driven into the uprights to provide an almost invisible but effective barrier to any birds wanting to perch on the rails.
For short distances between uprights you won’t need intermediate supports.
For longer lengths this simple support of two galvanised brackets seems to work well.