Actually, if using the negative association, Starlings and Seagulls are the “rats” of the bird world, Starlings being the most damaging and invasive bird in North America… And, you should check out the CDC website as to how many diseases you can get from a pigeon as opposed to a cat or dog. The “dirty bird” belief is actually a myth. The “rats with wings” statement was coined by the head of the NY dept of parks in 1963. He said “the biggest problems in the parks are the homeless, immigrants and pigeons. They’re all rats, but at least the pigeons are rats with wings”.
You should read Colin Jerolmack’s “The Cultural-Spatial Logic of Problem Animals” who states “It is the low status of animals like the pigeon that enables the thought of killing them to be funny.”