Vulture Hock

Vulture hocks are a gene that causes the feathering down the thigh and shank to come to a point well past the hock (3). It is likely correlated to the ptilopody (foot feathering) gene, but is not the same (1)(3). Not all breeds with the foot feathering gene have vulture hocks, but all bird with vulture hocks are ptilopodyl (1).

It is believed to be the same gene in both pigeons and chickens, with both species sharing the same inheritance and general characteristics of the mutation (2)(1), but no linkage tests have been done to prove the gene, chromosome, or locus of pigeons and no hybridization tests have been able to confirm this theory.

While it is not believed to cause any health issues in poultry, it is only recognized in certain breeds for aesthetic purposes. Widely believed to be a simply recessive gene (1), there is some controversy over whether the vulture hock may actually be an incomplete dominant trait (7)(8), or a trait caused by multiple genes working together (3).

The gene itself, while it cannot be traced back to the ancient junglefowl that chickens originated from, is very similar to genes found in fossils of the Microraptor Gui (9). There are currently studies being done to study the muscle growth and development in poultry with vulture hocks to see if they correspond with growth patterns of dinosaurs, and the possible devolution of additional wings (3).

The APA requires vulture hocks in the Booted Bantam, d'Uccles, Silkies, and Sultan. It is also naturally found in the unrecognized breeds of the Breda fowl and both the rare Ispemic and Bulgarian Dzhinka.

It is considered an extreme defect to the point of being a disqualification in all other breeds.

Breeding with Vulture Hocks:

Vulture Hock x Vulture Hock = 100% Vulture Hock offspring

Vulture Hock x Feathered Foot = 100% Vulture Hock Carriers (VHC)

Vulture Hock x VHC = 50% Vulture Hock, 50% VHC

VHC x VHC = 25% Vulture Hocked, 50% VHC, 25% Feathered Feet

VHC x Feathered Feet = 50% VHC, 50% Feathered Feet

Using the chart above, we can see that vulture hocks are particularly difficult to breed out. It is impossible to tell a bird that carries one copy of the vulture hock gene from a bird that is just plain feathered feet without very strong records keeping and test breeding. To read up on how to breed out recessive traits, please see the blog post linked here.