Found this link: http://www.araucana.net/introaraucana/
Here is what they say:
Tufts technically called peduncles (gene Et, autosomal dominant), appear as upturned feathers, that protrude near the ear on the birds. They are basically an organ attached to the bird’s body that protudes or flowers in stalk-like manner. This explains why they are either there or not — they do not appear as the bird ages but are there from the start.
They also some in several types including ST (single tufted) or DT (double tufted) as well as shapes. It is preferred by most fanciers that they are the double tufted and required for exhibition. Unfortunately, tufts are autosomal (not sex linked), dominant and lethal particularly when paired, so that the chicks die literally in their shell (DIS) during 17-19 days of incubation. Some do hatch, though most of these die within a week from what is commonly described as a “failure to thrive”. If things were not complicated enough, post-hatch mortality is also significantly greater among tufted chicks than among non-tufted chicks. Where most breeds get hatch rates of 90%; Araucana breeders get successful hatches (double tufted & rumpless) of anywhere from 55% to 25%, including the posthatch period.
....
From what I understand, it isn't just extra feathers, but a mutation causing a growth. Probably a double mutation is connected to other mutations inside the body. Possibly issues in the brain or other growths or deformities. It's like how white boxers (the dog) are often deaf because the lack of pigment in the brain leads to developmental issues. Same with how lethal white hamsters (two copies of the lethal gene) generally die before birth but sometimes are born missing eyes, limbs, etc.
Here is what they say:
Tufts technically called peduncles (gene Et, autosomal dominant), appear as upturned feathers, that protrude near the ear on the birds. They are basically an organ attached to the bird’s body that protudes or flowers in stalk-like manner. This explains why they are either there or not — they do not appear as the bird ages but are there from the start.
They also some in several types including ST (single tufted) or DT (double tufted) as well as shapes. It is preferred by most fanciers that they are the double tufted and required for exhibition. Unfortunately, tufts are autosomal (not sex linked), dominant and lethal particularly when paired, so that the chicks die literally in their shell (DIS) during 17-19 days of incubation. Some do hatch, though most of these die within a week from what is commonly described as a “failure to thrive”. If things were not complicated enough, post-hatch mortality is also significantly greater among tufted chicks than among non-tufted chicks. Where most breeds get hatch rates of 90%; Araucana breeders get successful hatches (double tufted & rumpless) of anywhere from 55% to 25%, including the posthatch period.
....
From what I understand, it isn't just extra feathers, but a mutation causing a growth. Probably a double mutation is connected to other mutations inside the body. Possibly issues in the brain or other growths or deformities. It's like how white boxers (the dog) are often deaf because the lack of pigment in the brain leads to developmental issues. Same with how lethal white hamsters (two copies of the lethal gene) generally die before birth but sometimes are born missing eyes, limbs, etc.
