2. Mutations‎ > ‎

2.5 Grizzling Factors

  There a many mutations that cause a grizzling effect on the feathers of the pigeons. Grizzling is usually described as a salt and pepper effect. This means that white and color patches can be seen on the same feather (though some grizzling factors do cause some feathers to be white and others to be colored). There are different kinds of grizzle, and are considered to be allelic (mutations at the same locus).

Note: I have no reference material or personal breeding results relating to the grizzle genes (other than classical grizzle), if anyone does and is willing to share pictures and reference materials, please let me know (leave a comment)

Grizzle

  Classical grizzle is ubiquitous with the Dragoon breed. This grizzle removes color from the proximal part of the feather (the part closest to the pigeon's body). Looking at a single grizzled feather, one would see a white base, a grizzled center and lastly a fully colored tip and outside edge. Grizzle is an incomplete dominant allele, with the symbol G, with g+ being the symbol for wild-type allele at this locus. Grizzle is an incomplete dominant since the homozygous birds (G//G) look different from those heterozygous for the trait (G//g+).

Heterozygous Blue Bar Grizzle Valencian Figurita (Photo by Jim Gifford)

Grizzle interacts differently with different patterns. The lighter the pattern on the pigeon, the more heavily grizzle is expressed. This means that a T-pattern grizzle will show visible grizzling only around the head and maybe on the neck and breast (and when spreading the wing or tail it would be possible to see the grizzle effect on the flights and tail feathers as well). While on a bar pattern, the grizzle would extend to the wing shield (as seen in the Figurita above). Spread also limits the expression of standard grizzle to some degree, giving rise to birds that are often called pepper-heads. These birds have a salt and pepper look on their heads only, while the rest of the bird seems black.

Heterozygous Blue Check Grizzle Racing Homer Hen (Author's Own)

Homozygous grizzle birds show what is called a stork marking. Color is limited to the head, neck and the ends of the long feathers (the flights and tail). A picture follows.

Homozygous Blue Grizzle Budapest Highflier (photo by Jim Gifford)

  The Aviphillia website has a very good picture of a homozygous blue grizzle (I cannot use it in this site due to copyrights).

Tiger Grizzle

  Tiger grizzle is an allele of grizzle, symbolized by (GT). Tigered birds do not show the grizzling on each feather, instead causing fully colored feathers and white feathers side by side, giving an effect similar to normal or classic grizzle. This mutation is also an incomplete dominant, and homozygous birds end up being almost pure white. Tiger grizzle birds are born with almost normal feathering, but moult into more white in their adult plumage.

Blue Spread Heterozygous Tiger Grizzle King (photo by Jim Gifford)

  Tiger grizzle and classical grizzle together will produce both phenotypes. This means these two alleles are co-dominant (both expressing at the same time, and both dominant to wild type).

Other factors

  • Undergrizzle (Ug) - An incomplete dominant that has similar but less extreme effects than classic grizzle.
  • Drizzle (Drz) - An incomplete dominant mutation (studied by Larry Long)
  • White Grizzle (GW) - A grizzle factor that shows much increased amounts of white.

White Pied (Splash) versus Grizzle

   It is very important not to confuse grizzle birds with pied birds. Pied birds have a patchwork appearance, with the areas between colored feathers and white feathers (mostly) clearly delimited. There is never a grizzling effect on individual feathers. Pied birds do not moult into their white plumage like tiger grizzle, but have white in their nest plumage as well.

  It is also possible for a bird to be both pied and grizzled, and in some cases can only be proved by performing breeding tests. Below is a racing homer that shows a white pied phenotype as well as grizzle.

Young White-Pied Blue Check Heterozygous Grizzle Racing Homer
(bred and photographed by Becky Mishak)

Grizzle and Bronzing

  Grizzle can also act as a bronzing agent though the mechanism of this bronzing is not well understood. These bronzed grizzles show bronzing in the colored parts of the feathers, especially those parts of the feathers that would make up the pattern of the birds. The result is a bronze and black barred grizzled blue, often called tortoiseshell.
 
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