Description:
The beard and muff gene in chickens causes the bird to present feathers from the side of the head around to the bottom of the beak, creating a "beard" like look. The muff is defined as the feathers from the side of the head, and the beard is the feathers directly under the beak, though they are both controlled by the same gene. This mutation also causes the wattles on the bird to shrink somewhat and be covered by feathers.
In heterozygous form (one copy of beard and muff), the bird will just have a smaller beard and muff, with shorter feathers than the full bearded counterpart. The fuller beard is almost always preferred.
APA Recognized bearded breeds include the Polish, Silkie, all of the Belgium Bantams, Favorelles, Ameraucana, Sultan, Crevecour, and Houdan.
Breeding with Beards: For more information about breeding with this kind of gene, including tips and tricks and a full explanation of how these results were calculated, please see here.
In this case, it is called Bearded just to shorten it, but it refers to both the beard and muffs on a bird.
Bearded x Bearded = 100% Bearded
Bearded x Non-Bearded = 100% Partial Beard
Bearded x Partial Beard = 50% Bearded, 50% Partial Beard
Partial Beard x Partial Beard = 25% non-Bearded, 50% Partial Beard, 25% Bearded
Partial Beard x Non-Bearded = 50% Partial Beard, 50% non-Bearded
References & Further Reading
Guo Y, Gu X, Sheng Z, Wang Y, Luo C, Liu R, et al. (2016) A Complex Structural Variation on Chromosome 27 Leads to the Ectopic Expression of HOXB8 and the Muffs and Beard Phenotype in Chickens. PLoS Genet 12(6): e1006071. https://doi.org/10.1371/journal.pgen.1006071
Dementieva NV, Shcherbakov YS, Ryabova AE, Vakhrameev AB, Makarova AV, Nikolaeva OA, Dysin AP, Azovtseva AI, Reinbah NR, Mitrofanova OV. Comparative peculiarities of genomic diversity in Gallus gallus domesticus chickens with decorative plumage: the muffs and beard phenotype. Vavilovskii Zhurnal Genet Selektsii. 2024 Feb;28(1):108-116. doi: 10.18699/vjgb-24-13. PMID: 38465249; PMCID: PMC10917671.
Somes, Ralph G. Jr., "International Registry of Poultry Genetic Stocks" (1988). Storrs Agricultural Experiment Station. 29. https://digitalcommons.lib.uconn.edu/saes/29