[MontyCarloHall]

You are correct; birds are not sensitive to capsaicin [0]. Seems this is specifically confirmed for pigeons [1].

Perhaps the cinnamon or vinegar are the true repellents?

[0] https://pubmed.ncbi.nlm.nih.gov/11853675/

[1] https://pubmed.ncbi.nlm.nih.gov/3797018/