I've seen a number of pheasants over the years that had a lot of white on them like the one pictured. I think it's just some mutation. Back in 1980 we were driving down a gravel road out here in SD and spotted some pheasants in the ditch up ahead. There was one white pheasant in the bunch. They ran into the weeds so we got out and jumped into the weeds. The whole bunch flushed and I shot the white one. Turned out it was a hen, but how could you tell? It was totally white, not one dark feather on it.
Hope I'm not incriminating myself by admitting I shot a hen?? But since it was 30 years ago the statute of limitations has probably run out. And besides, where's the evidence?