Description:
The ear-tuft gene in Japanese quail is very similar to the tufted mutation in chickens, though it presents as a simple recessive gene instead of incomplete dominant (2) and is not entirely lethal. It causes the quail to grow feathers from the side of its face in a similar manner to the throat-tuft gene also found in quail, though the feather placement will be slightly higher on the skull and thus much more extreme (3).
It also causes major structural changes to the head of the bird itself, including a curved head shape (in the more extreme cases, the skull forming a club shaped fusion in the embryo), slightly misshapen or even missing portions of the jawbone, and an overall more angular look to the head (1). About half of the birds in studies displayed noticeable and major skeletal changes to the head because of the ear tuft mutation (1). The feathers coming directly from or slightly below the ears also impacted the ear canal itself, leading to a collapsed ear canal and overall issues with hearing on about 90% of birds with the ear tuft gene compared to a much lower rate with the throat tuft gene (2). Birds can still live perfectly normal lives and reproduce despite any abnormalities caused by the ear tuft gene, and studies have shown that these defects can repair themselves during growth (4).
When the ear tuft gene and throat tuft gene are crossed, the birds tend to inherit the structural issues from both, and it leads to a wide array of extreme issues. Most common are large holes near the ear tract where the canal should be, collapsed jawbones, and bones protruding from the side of the face along with feathers (3).
It is not formally in public hands, though birds with feathers appearing from the neck have been documented several times outside of labs and do exist (5)(6). It is unknown whether this is the ear tuft gene, the throat tuft gene, or even a separate mutation entirely. Birds in the same line also tend to have feathers on the back of the head. (6) It appears that the feathers coming from the throat also display the similar patterns to the breast plumage.
Breeding with Ear Tuft:
Ear Tuft x Ear Tuft = 100% Ear Tuft
Ear Tuft x Normal = 100% Ear Tuft Carriers (ETC), these look like normal birds
Ear Tuft x ETC = 50% Ear Tuft, 50% ETC
ETC x ETC = 25% Ear Tuft, 50% ETC, 25% Normal
ETC x Normal = 50% ETC, 50% Normal (all will look like normal birds)
References & Further Reading
TSUDZUKI, Masaoki, and Noboru WAKASUGI. "Genetic Head-Skeleton Abnormalities in the ET (ear tuft) Strain of Japanese Quail A Defect Associated with the Incomplete Closure of the Hyomandibular furrow." Japanese poultry science 25.4 (1988): 207-217.
Tsudzuki, M., and N. Wekasugi. "A genetic defect in hyomandibular furrow closure in the Japanese quail: the causes for ear-opening abnormality and formation of an ear tuft." Journal of Heredity 79.3 (1988): 160-164.
TSUDZUKI, Masaoki, and Noboru WAKASUGI. "External and lnternal Abnormalities Exhibited by the Crossbreds between the Ear-Tuft (hfd) and Throat-Tuft (hfdTt) Mutants of Japanese Quail (Coturnix coturnix japonica)." Japanese poultry science 28.3 (1991): 131-141.
TSUDZUKI, Masaoki, and Noboru WAKASUGI. "Repair of the hyomandibular furrow closure defect in the ET strain of Japanese quail." Japanese poultry science 25.5 (1988): 278-287.
Estrada, Alex. Facebook, Coturnix Quail Colors and Genetics group, November 17th 2024. "Post discussing quail genetics." Accessed August 2, 2024. https://www.facebook.com/groups/550750305134029/permalink/708846385991086/.
White, Kate. Facebook, Coturnix Quail Colors and Genetics group, March 31, 2020. "Post discussing quail genetics." Accessed August 2, 2024. https://www.facebook.com/groups/550750305134029/user/100025081121061.