I have some limited but interesting observations from my own flock.
We had a bobcat that moved into our area during the fall. She was killing about a bird per week until a neighbor shot her (not at our request). Those were the only birds we ever lost and we haven't lost any since.
We had a mixed flock of 6 each of naked necks (various colors), black australorps, and buff orpingtons, all free ranging together. We lost 5 black australorps, 4 naked necks, and 0 buff orpingtons. The difference in mortality among groups is statistically significant.
I'm guessing the main factor was just color. Fall in Arkansas is orange-brown, about the same color as the buff orpingtons. The naked necks that survived were orange-brown and red-brown. The naked necks that did not were black, and white.
Maybe camouflage is at least as important as breed behavior.