So in regards to the project, this has actually been revealing. I'm down to two Kraienkoppe boys. The dogs haven't gotten any of the others. One attempt on a fat Ranger hen, which I interrupted.
Other than that, only Kraienkoppe have been taken, all low level cockerels. Feathers have been found in grassy areas, not under trees or bushes.
I didn't hear any of the attacks, but each time was alerted by the Dorking-Sussex cockerel.
Could be a lot of reasons. The male Kraienkoppe coloring is distinctive, but I don't think it's that. They are smaller birds, and the Kraienkoppe tend to be more skittish, running at the slightest scare--often in just the wrong direction.
Most of the other birds are dark or mottled, and don't scare worth a darn. If startled they're more likely to freeze than run. The smallest are also easily 2-3 times the size of the largest Kraienkoppe.
I think it's a combination of size (toy that's too small to effectively fight back) and movement, matched with the birds' inexperience.