i don't think its color really it might and i could be wrong because with my birds i have all different colors barred rocks sorta have the same coloring as dorkings and they don't stay by each other and i have cross bred barred rocks and some are mostly dark grey then and the others are normal color and then i have 3 barred rocks that sleep away from the flock with 1 red hen and then 1 barred rock that sleep with my black australorps and i have a white crested black polish and she doesn't hang out with my black australorps and then i have a mottled houdan if you don't know what it is its like a bigger size polish and he is black and white and he hangs out with the cross bred barred rocks and sometimes my pure black birds and he doesn't look like them