You'll need to get some more plants and net them to keep the pigeons off.

How about staking several parallel lines over the plants and taping aluminum strips to the lines so they hang vertically. The reflection and motion kicked up when they try to land could scare them off.

Netting is far more likely to be successful Loosestrife our pigeons aren't at all bothered by CDs suspended from lines

Thanks Moon growe. I did have then netted but somehow it had got open and in they went!!!!
Thought it might be a new set of plants but was checking?

In any case hang CD's and blast them with a good dose of Led Zeppelin.

You obviously don't know how tenacious our pigeons are Loosestrife!