Catching a pigeon is extremely difficult and risky, as demonstrated in this short documentary on the subject.
Ducks (and bears) that eat a lot of salmon eggs taste horrible, like rotten fish. Wild hares that live close to cities are noticeably different, and have a worse taste than wild hares with no human influence.
Hmm… the above posts have me thinking cows should be fed Montreal seasoning.
Mmmm… Squirrel Chili! 
Surely city pigeons are the same species as that which we raise and butcher and serve as squab. Squab is about my favorite meat in the whole world - it tastes a lot like foie gras.
However, fattening the bird in captivity with grain and in clean conditions is a lot different than feral birds eating trash. I’m sure there’s a big taste difference.
When I was an undergrad, I worked for an environmental science firm that did inspections of abandoned buildings and property slated for redevelopment. In downtown St. Louis there are a plethora of these to walk, so I’ve seen my fair share.
I can’t tell you how many squater fires we walked up on that had piles of pigeon carcasses laying around. Seriously, if I had to guess a number, a thousand wouldn’t be an exaggeration. So by my reasoning they couldn’t be that bad.