Fallow in the Turquoise Parakeet

What is the Fallow mutation?

Fallow is logged in this calculator's reference data as an autosomal recessive melanin mutation with red eyes, kept as a distinct locus from Dun Fallow and Faded even though all three belong to the same general "fallow-family" pattern seen across parrot species (red eyes plus lightened melanin). Species that carry multiple fallow-type mutations — cockatiels are the most studied example — treat each named variant (bronze, dun, ashen and so on) as genetically distinct, which is the same approach taken here.

How it works, in plain terms

Fallow-family mutations partially disable the pathway that produces and darkens eumelanin, in both the feathers and the eyes. With less functional dark pigment in the iris and retina, the eye reads as red or plum instead of the normal dark brown/black — a reliable field mark, visible even in young birds. In the feathers, black areas soften toward a warmer or greyer tone depending on exactly which fallow-family mutation is involved.

Autosomal recessive inheritance, explained

Fallow sits on an ordinary autosome, so cocks and hens inherit and can carry it identically. As a recessive trait, it takes two copies to show:

• One copy (split) — the bird looks completely normal but can pass the mutation to offspring.
• Two copies (visual) — the bird shows red eyes and lightened coloring.

Genotype → phenotype