It’s the morning of June 12th, 1944 and a pigeon named Paddy is making an epic 368 kilometer journey. He manages to dodge Nazi falcons then beats on through stormy weather, flying an average of 79 kilometers per hour for almost five hours straight. Paddy’s carrying the first news  of the D-Day invasion back to England. He wins a medal for gallantry for this accomplishment. Paddy was one of around 250,000 pigeons used by the British during World War II to speedily transport secret messages. In fact, pigeon delivery systems are ancient human practices. Seeing their meat as a protein source and their nitrogen-rich poop  as the perfect fertilizer, humans brought pigeons into captivity as far back as 10,000 years ago. We then tapped into other traits. Pigeons are naturally speedy  and possess a powerful homing instinct that drives them to navigate long distances back to the location they consider “home.” So we began developing pigeon posts and breeding and training them for racing. In a hobby called  “pigeon fancying,” people selected for traits  like head plumage and fabulously feathered feet. As we carried pigeons around the world, they escaped or were released, forming the wild urban flocks we're familiar with today. Pigeons are now one of the most abundant, widespread species on the planet, managing to thrive in chaotic cities. They owe their success to an ideal combination of traits, including some that were accentuated by humans. Unlike birds that nest  on the ground or in trees, pigeons were originally cliff-dwellers. City buildings mimic  their natural habitat. And pigeons set a notoriously  low bar when it comes to homemaking. Add some sticks to any window ledge or highway overpass and it's a great spot to raise babies. This unfussiness allows them to live  in environments where more specialized species can’t. As generalists, pigeons take advantage  of urban food waste. With an organ in their throats  called a crop, they can gorge themselves when food is available and store some for later. They provide “crop milk” to their young instead of having to fetch them live food. Chicks grow quickly with this  fat and protein-rich meal. If conditions are right, pigeons breed year-round and produce new offspring every six weeks. They actually have higher breeding rates in cities because of the abundance  of food and shelter. These booming populations  attract predators. New York City is home  to a million pigeons, which support large populations of raptors. But pigeons’ aptitude for swift flight, further exploited by being bred for racing, means they’re made  for high speed chases. Compared to barn owls, which are a similar size, pigeon wing bones are thicker  and more curved, providing extra space for muscle mass. They can reach speeds  of 125 kilometers per hour. And their large flocks ensure safety in numbers and more eyes on the lookout. While pigeons play a starring role in urban wildlife, we’re not always enthusiastic neighbors. In 1966, New York’s parks commissioner coined the term “rats with wings” and it stuck. Indeed, their poop, which we originally cherished  as fertilizer, presents a unique problem. Just one pigeon can leave behind  11 kilograms of acidic excrement per year, which, in the United States,  scales to about $1.1 billion in structural damage annually. Though incidents of infection are rare, this poop can host fungi  that are harmful to people if inhaled. They may be numerous, noisy  and a little too keen on your lunch, but the pigeons that swirl around us are evidence of an ancient,  ongoing relationship. Their rise to world domination has been a collaborative effort. For better or for worse,  we did this to ourselves.