I just read "Pigeons" by Andrew Blechman, which uses pigeon racers as its main through-line. Among other interesting facts in there: the pigeons you find in cities are not wild animals, but feral ones - they are all descended from domesticated animals. That has practical consequences because for example it's illegal to hunt wild animals in New York City, but the law doesn't apply to feral animals. Thus, there are (or were, when the book was written a few years ago) people who throw big nets over pigeons in NYC and sell them for a few bucks apiece in Pennsylvania, where they are (legally, still) shot for sport.