In the wild, all individuals of a species usually look much the same. Robins, for example all have gray backs and red-orange breasts. All crows are black. But the pigeons we see around the world are a different story. They show remarkable color variation, just like cats and dogs. Why? They are all descended from the blue-bar Rock Pigeon (to learn about color-morph definitions, click here), but over hundreds of years pigeons were selectively bred by humans for their colors, homing instincts, or racing abilities. As a result, captive flocks of different-colored pigeons were established all over the world. Eventually, captive birds escaped into the wild to become the feral, common pigeon flocks we see today.

Feral pigeons have adapted to life in cities, in suburban parks, on beaches and on farms. They have had established populations in North America for 400 years and on other continents for much longer. And despite this, their populations continue to have individuals of many different colors. They have never reverted to the colors of their wild relatives in the Mediterranean and beyond. No other feral animal has kept so many domestic colors for more than a few generations.

Scientists believe there are at least three possible explanations why there are so many colors of pigeons across the world:

1. They don't have many natural predators in cities. Predators tend to attack the "odd one out". For example Peregrine Falcons or hawks will kill the one red bird in a flock of blue-bars. But in cities, there are few predators to eat the colorful or odd-colored birds. Therefore these birds may survive to breed and pass their unusual colors to the next generation.
2. Food is abundant in cities. When food is in short supply, animals will fight among themselves to get it. The winners (the dominant individuals) get to eat first. If blue-bars, for example are dominant, they will win all of the food fights and thus be the only birds that can survive and breed. But in cities, where food is plentiful, food fights would be few, and all morphs would be able to survive and breed.
3. Assortative mating. Maybe multiple color morphs continue to persist because city pigeons choose mates by their colors. For example, some birds may choose mates of their own color. This is called assortative mating. Others may prefer mates of different colors. Because colors are inherited, the colors of parents will determine the colors of their young.
   

Observations made by PigeonWatchers counting the different color morphs and recording the colors of courting pigeons in many different cities can help scientists learn:

• why pigeons continue to exist in so many colors
• which color morphs pigeons prefer for mates

To learn more about studying pigeons, click here.