You know, could be the silkie in question is a dwarf, but of a type I'm not familiar with--see article below. There are several types of dwarfism in poultry, but the two I cited, I believe, are the most common. The one type that I described with curved toes and beaks usually don't live to adulthood and there is a lethal gene associated with it if you breed two together. The once-in-a-lifetime type usually do fine. Gosh, I wish I could remember who hatched that dwarf BR from me. She kept him as a pet, but I cannot find the thread. It was a couple years ago.
Here is a blurb from an article on Poultry mutations:
Dwarfing Genes:
There have been four loci identified with dwarfing mutations, one locus with multiple mutation alleles:
Z
rg
adw
dw, dwM, dwB
* Z "Dominant Sex-linked Dwarfism" found in Golden Sebrights (Maw 1935, crossed Light Brahma with Gold Sebrights).
* rg "Recessive Sex-linked Dwarfism" Black Rosecomb Bantams (Godfrey 1953, crossed Barred Plymouth Rock with Black Rosecomb bantams)
* adw "Autosomal Dwarfism"- mutation occurred in Cornell K strain White Leghorns (Cole 1973)
* dw, dwM, dwB "Sex-linked Dwarfism"- closely linked to silver-gold & slow-rapid feathering loci.
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- dw Mutation appeared in a New Hampshire flock (Hutt 1959)
- dwB found in Golden Sebright (Custodio & Jaap 1973) (dwB dominant over dw)
dwM found in a meat-type line (Hsu et al 1975). (inheritance relationship with other locus alleles not determined).
Generally large & bantam crosses produced F1 offspring intermediate in size (sometimes closer to bantam size). F2 offspring had the greatest variation in size. An exception was found in a study by Danforth (1929). There was variation between bantam breeds when he crossed a Millefleur Belgian d'Uccle Bantam male with Sebright females. Some F1 progeny were larger than the parents, & in later generations birds both larger and smaller than the parental types were obtained.
I haven't crossed Standard size to bantams, but there is a lot of difference in size between various bantam breeds I have crossed, and sometimes there is obvious variation in sizes within a breed, between lines. Usually the first crosses are intermediate in size, but I've had results similar to Danforth, where F1 offspring were larger than both parent birds (eg Orpington Bantam X Indian Game Bantam, resulting F1 were close to commercial layer size, and unrelated d'Uccle X d'Uccle, some F1 offspring larger than parents, etc). Something that I thought was amiss in Poultry Breeding and Genetics was that there was little mention in the chapter of mutations that INCREASE size. Crosses were made between bantam breeds to large Standard size breeds, these much larger than the Red Jungle Fowl wild type. Obviously mutations that increase size would need to be taken into consideration when determining dwarfing genes.
There is another chapter in the book, dealing with studies on the dw gene, for possible commercial use. Usually these dwarfing genes have little in the way of deleterious effects to general health (sometimes heath gains), but of course there are few production issues, eg reduced egg size, body weights, etc (tend to be more efficient with feed consumption to production outputs though).
