A true breeding black fowl is crossed with a true breeding white fowl, and all the progeny fowl are neither black nor white. Is this an example of Mendelian inheritance?
This is an example of incomplete dominance. In this case black colour is incompletely dominant on white colour.
Generally the hybrid is described as 'blue' coloured and it is seen in Andalusian chickens.
Example of codominance is also there in chickens, where a cross between black and white yield checkered/speckled chickens.