Description:
The mottling gene in chickens creates a pattern of white spangles across the tip of usually black feathers (2). It is a fairly common mutation, and the birds will exhibit more white across the feathers and more white-tipped feathers overall as the bird ages (4). It has also been suggested that the mottled gene is the same as the recessive pied gene in chickens (5) (3).
It is completely recessive, meaning you will only see white spangling with two copies of the gene. It is often used in combination with other mutations to create varieties such as Millie Fleur (Mahogany + Colombian + Mottled), Speckled (Wheaton, Gold Dilute, Mahogany, Mottled), and Porcelain (Mahogany + Colombian + Lavender + Mottled) (2).
The APA recognizes the following breeds with mottling: d'Anver, d'Uccle, Cochin (bantam), Cornish (bantam), Houdan, Japanese, and Java (4).
They also recognize the following breeds with Millie Fleur: Old English, and these breeds with both Porcelain and Millie Fleur: d'Anver, d'Uccle, and Booted (4). Spangled is an accepted variety for Aseel, Cornish, Malay, Old English, and Sussex are recognized for their speckled variety. (4)
Mottled x Mottled = 100% Mottled
Mottled x Non-Mottled = 100% Carriers (will not appear mottled, but carries the gene)
Mottled x Carriers = 50% Mottled, 50% Carriers
Carrier x Carrier = 25% Mottled, 50% Carriers, 25% Non-Mottled
Carrier x Non-Mottled = 50% Carriers, 50% Mottled
References & Further Reading
Kinoshita K, Akiyama T, Mizutani M, Shinomiya A, Ishikawa A, Younis HH, et al. (2014) Endothelin Receptor B2 (EDNRB2) Is Responsible for the Tyrosinase-Independent Recessive White (mow) and Mottled (mo) Plumage Phenotypes in the Chicken. PLoS ONE 9(1): e86361. https://doi.org/10.1371/journal.pone.0086361
SOMES JR, RALPH G. "The mottling gene, the basis of six plumage color patterns in the domestic fowl." Poultry science 59.7 (1980): 1370-1374.
Li, Jingyi. "Gene mapping of morphological traits in chickens." (2017).
American Poultry Association. (2023). American Standard of Perfection (45th ed.)
Carefoot, W. C. (1987). Evidence that the mottled (mo) and pied (pi) plumage genes of the domestic fowl are identical. British Poultry Science, 28(4), 753–754. https://doi.org/10.1080/00071668708417013
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