A common question in relation to breeding is: what will be the outcome of crossing a black to a white fowl? The answer to which, no-one really knows. This may seem a bold statement, but there is an explanation...
The outcome of a proposed black to white, or vice versa cross, is largely dependent on the breed in question, and whether the cross will be between the black and white versions of that breed or whether the birds intended for breeding are pure for their respective colours but are different breeds.
For example, from a feather point of view, the results of crossing a white Wyandotte bantam cockerel to a black Wyandotte pullet would differ greatly from crossing a white Croad Langshan bantam cockerel to a black Wyandotte pullet.
Why is this you may ask? It all comes down to the fact white chickens can be any number of genetic combinations beneath the white plumage. They could carry blue, barring, dominant white (the type required for pile), silver, gold, columbian, lacing, and the list goes on. The 'white feathered' fowl sat before you could have the genetic base of any variety of poultry you can think of.
Over time, it has been established that 'generally' certain white breeds are specific genetic combinations, which are decidedly different from those of other white breeds. However, the only 'true' way to test what a white birds carries is to cross a coloured bird to it and monitor the results. The best that one can hope to advise is, for example: "Crossing a black to a white version of this breed will 'likely' yield the following results." It is not possible for anyone to make statements of surety unless they have tested the actual birds in question, let alone the breed proposed for crossing.
Some breeds that have white versions in both large fowl and bantam can be different genetically from each other. An example is the Wyandotte, where the large fowl are believed to be laced under the white, whereas the bantams are generally 'barred-partridge' beneath the white.
White 'sports' sometimes emerge from non-white fowl, which can be confusing for the newcomer. It can be perplexing too for the experienced poultry breeder. A case occurred recently in a line of large fowl black Wyandottes that have been bred pure for years - this year the breeder saw two yellow chicks hatch, as well as the expected black ones, and these turned out to be white sports. To all intents and purposes, they are white Wyandottes with only slightly tighter feathering than the white exhibition stock.
With such birds, their genetic make up for plumage is known, and is that of a solid black bird since they came from black Wyandottes. You may ask what purpose they have for breeding, and my response would be: very little. Bred back to the father of such birds, it would produce half blacks, and half whites in the offspring.
It is also worth noting that perpetuating the white genes in black fowl is not a good idea, unless you are prepared to endure the one quarter white chicks which will emerge in future generations of black to black birds.
White sports also emerge from the silver laced variety of Wyandotte and hence the reason they are regarded primarily as 'laced' beneath the white plumage, which they generally are. The white variety of Wyandotte was actually developed from such sports - it wasn't a difficult task, as any sports would breed true - 100% white offspring produced when bred together.
The white genes are required for colour in the exhibition partridge Wyandotte cockerels. This may seem odd and perplexing, but the particular shade of lemon requested by the standards means that the correct exhibition birds need to carry a single dose of the white gene - although not visible as white, it emerges in 25% of the offspring, which are completely 'self-white.' Again, we know that such birds are genetically 'partridge' because of their ancestry.
The most fundamental point to remember about any form of white fowl is that unless it has been tested for the genes it carries, it can only be guesswork as to what it will produce when crossed with any form of 'non-white' fowl.
Whites are best bred to whites, and unless you want more unexpected whites out in future, you will leave out the idea of crossing to other colours. Some people believe that crossing blacks to whites will produce all blue offspring, and very occasionally it does. However, my advice would be: if you fancy blue fowl, go out and buy yourself some - you will save a lot of time and effort, as the chances of producing them from blacks and whites are very slim.
Self blue fowl when bred together will produce about one quarter 'Splash' fowl, which are predominantly white, but with flecks of black and blue pigment 'splashed' randomly across the body. Such birds when bred to blacks will produce all blue offspring, but they are splashes, and not whites - a point I feel which is essential to grasp before any crosses are made.