I'm not aware of any contaminant that builds up in the breast tissue of birds where it would be enough to be a concern... urban or rural. Especially "big cities" in North Dakota. In my career as an "environmental chemist" I've never come across a presentation or paper that documents such a contaminant.
Numerous peer-reviewed studies of contaminants suggest any concerns are unfounded. Probably stemming from a "filth phobia" that is generally a useful innate fear. A fear that is probably ancient in origins - when not cooking/handling properly combined with poor hygiene (poop on your meat) killed or sickened those who didn't pay attention to "filth phobia".
It's not like pigeons eat poop/chemicals guys... they eat grains, fruit, and maybe an invertebrate now and then. And maybe some bread, french fries, popcorn or something they MIGHT stumble upon occasionally in the big cities of ND.
You pigeon loathers look a little like cavemen - "ugh... bird poop bad... pigeon bad... me no eat pigeon".
MAYBE "pigeon liver bad in Bangladesh or some horrible place..." but not breast meat.
Exhibit A:
http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.1022.2734&rep=rep1&type=pdf