Yes it is illegal. Chicago is the only large city in the United States to enact such a ban.
No, that is not really accurate. Certain residential areas are zoned to make it unlawful to raise pigeons, but there are pigeon clubs in the city and pigeon lofts. Any person can keep pigeons in a non residential area. See Municipal Code of Chicago, Chpt. 7-12-387.
It is not unlawful to feed wild pigeons in Chicago either. It is unlawful to scatter or dump seed or vegetable matter where rats can find it, but if you feed them by hand or make certain they eat all that is given with no waste, not illegal.
Why not let it go? They don't call them homing pigeons for nothing.
millions of pounds over a span of many trips
There is about 69 to 84 types of pigeons