If you ask at a meeting of zebrafinch lovers a question about the genealogy of the masked, the pastel, or a black cheek, you are sure to receive the right answer.
But if we ask the genealogy question about the format (size), the shape of the head or the length of the beak, the answers will be multiple and different.
Some will say intermediaries, others dominant, etc.
Nevertheless these characteristics follow Laws of Mendel. Many breeders do not believe this explanation, but it is true. It seems that the laws no longer behave in a strict way as for the mutations of colors. A wider variation in the format (size), shape of the head, etc... seems normal.
In nature, zebrafinch have the same variation in size. And, in the process of domestication, this difference in variation has increased. Our cultivated zebrafinch are on average two centimeters wider than their ancestors in nature.
In the articles, we always recommend a hard selection at the level of format and model taking into account the differences between the parts such as the head, the body, etc.
But the format and the model are driven by genealogy. The body shapes are driven by factors.
The question that arises is: Is there a relationship between the different factors that govern the format, the model, the shape of the head and the beak ?