De Ross book - male. A black area with sooty blending into brown which is slightly darker than the back colour - not paler. The photo quality in this book is a bit ancient too - on the same page the cock Melba's face is pink & the male OB's back is black. Perhaps Russell Kingston's earliest book is a more accurate indicator with likely better photo quality.Uraeginthus wrote:de Ross book: black belly
As with the original youtube video posted by Gary the differences between the black-bellied & brown bellied birds in the same batch are males & females.
I've never seen a male BH Nun without some black on the belly. The keys are how gradually it blends to the surrounding brown, the relative intensity of that brown & whether the black exists on females.