When observing the pigeons that inhabit our cities, the common assumption is that they are simply grey birds. The true coloration of the Rock Pigeon (Columba livia) is far more complex and varied. This single species is the ancestor of all domestic pigeons, and the vast array of colors seen in urban environments is a direct result of thousands of years of human domestication and interbreeding. Understanding pigeon color requires looking at the ancestral wild type, the variations in feral flocks, and the underlying genetic mechanisms that drive this diversity.
The Ancestral Rock Pigeon’s True Colors
The wild form of the Rock Pigeon possesses a distinct and standardized plumage, which serves as the blueprint for all other color variations. The primary body color is a pale bluish-grey, a shade that gives the species its scientific name, livia, which translates to “leaden” or “bluish-grey.” This wild coloration is now relatively rare in urban populations due to widespread interbreeding with domestic escapees.
A defining feature of the ancestral Rock Pigeon is the presence of two black bars that run horizontally across the pale grey wing. The lower back area, or rump, is a clean white patch, which is an important field mark for identifying the pure wild type. The neck and upper chest feathers exhibit a striking metallic iridescence, displaying glossy shades of green, purple, and reddish-purple that shift with the light.
This standard “blue bar” pattern is the genetic benchmark against which all other color mutations are measured. The pale grey pigment is distributed consistently across the body, with the denser black pigment restricted to the two wing bars and the terminal band on the tail feathers. The clarity of these markings in the wild form contrasts sharply with the mixed and muddied patterns seen in today’s city flocks.
Understanding Color Variation in Feral Populations
The multitude of colors and patterns observed in city pigeons, often called feral pigeons, is a direct consequence of their domestic history. Feral populations are descendants of domestic pigeons that escaped or were released and interbred with wild-type birds. This introduction of domesticated genes into the wild gene pool is responsible for the dramatic range of phenotypes seen across metropolitan areas.
The ‘checker’ pattern is common, where the two wing bars of the ancestral type are replaced by a dense, checkered appearance across the wing shield. This pattern is caused by a mutation that increases the amount of black pigment, spreading it into the areas that would be pale grey. A further increase in this pigment results in the ‘T-pattern check,’ where the wings appear almost entirely black.
Pigeons also exhibit solid color morphs, such as those that are black or reddish-brown. The solid black appearance, known as the ‘spread’ phenotype, is a dominant trait that obscures the underlying wing pattern. The base color can also be reddish-brown, often referred to as ‘Ash-Red’ in genetic terms, which is a common base color mutation introduced through selective breeding.
Beyond these base color and pattern variations, you will frequently encounter pied or mottled pigeons. The pied pattern is the presence of unpigmented white feathers mixed with colored feathers across the body. This is caused by genes that prevent pigment from reaching certain feather follicles, creating the patchy, multi-colored birds seen foraging in parks and on sidewalks.
The Genetic Basis of Pigeon Pigmentation
Pigeon color is determined by the interplay of two types of melanin pigments: eumelanin and phaeomelanin. Eumelanin is responsible for the black and grey coloration, while phaeomelanin produces the reddish-brown and yellow colors. The specific color and pattern a pigeon displays are controlled by a few major genetic loci that dictate the type, concentration, and distribution of these two pigments.
The base color of a pigeon is controlled by a sex-linked gene that determines whether the bird will be Blue/Black (the wild type), Brown, or Ash-Red. Blue/Black and Brown pigeons rely on eumelanin, while Ash-Red pigeons produce phaeomelanin for the reddish color. The blue coloration of the wild type is not due to a true blue pigment but rather a structural effect where clumped black eumelanin granules refract light to create a bluish tinge.
Another group of genes controls the wing pattern, which includes the Bar, Check, and T-Pattern Check series. These genes govern how much eumelanin is deposited on the wing shield feathers, creating the contrast between the pale background and the darker pattern. The Bar pattern is considered the wild-type standard, while the Check and T-Pattern Check are dominant mutations that progressively increase the area of black pigment.
Modifying genes refine the final appearance, including the ‘Dilute’ and ‘Spread’ genes. The Dilute gene acts by halving the intensity of the base color, turning Blue/Black to a lighter Silver and Ash-Red to Yellow. The dominant Spread gene takes the dark pigment from the tail-band and spreads it over the entire body, converting a Blue Bar pigeon into a solid Black one by masking the wing pattern.