I thought I'd done everything right. Raised my new chicks indoors for 6 weeks. Moved them out to the coop to an area that was separate from the big hens (2 years old), but only through fencing, so they could see, hear, etc. One week in that space, then made an entry so the chicks could have the run and their space, and the hens stil had the coop and could go out for free ranging. That's gone on for another 2 weeks. I've let the chicks out for ranging for an hour at a clip in the evening, and I am really shocked at how aggressive the Wyandottes are to the babies!!
The Buff Orpingtons act the way I expected, pretty much ignore them unless they get too close and then snake a head. But the Wyandottes will wait for them to get out of the run, and come from wherever they are to actively chase the chicks. One of the caught one, held it down with one foot and pulled out all of the tail feathers. I thought they would get over it, but it's been a week of this and they are not easing up. Not sure I am ever going to be comfortable putting them in the coop together whether the Wyandottes could get the babies pinned!!
I am never getting anything but Orpingtons again!