The black coloration is caused by hypermelanosis.
This over-coloration of their feathers, in contrast to the normal chicken we usually see, produces black and dark grey traits within these species, making them almost blue-black in color.
Hypermelanosis is a genetic mutation that results in the formation of too much melanin – cases like this are rare amongst animals species, however.
Thankfully, this unique gene ‘condition’ doesn’t harm the chicken at all, it just makes everything about them black.
The chicks are born completely black! See – even the inside of their mouths are black. Check out the metallic sheen on those feathers!
