Presumably you are in the US, as we don't have cardinals here in the UK (except for the occasional rare migrant/escapee). They are the equivalent of sparrows here (very common), but are much more attractive i.e. bright red plumage with a crest.
I don't know WHY you would want to get rid of them - they are just sharing your neighbourhood as they are entitled to do.
Perhaps they are wondering how to get rid of the unfriendly humans in your area - they have probably been there longer than you and it is you who are the interlopers!!!