Congratulations on getting the two banded birds and the and the hybrid duck! Last week we dropped 4 Cacklers out of a small flock. One of them had a white ring around it's neck. IMG_8832 by , on Flickr I have seen the white rings around the neck before but they were on bigger birds.
I’m no biologist but it would seem to me that in the scenario of two breeds crossing there wouldn’t be hard fast rules as to what the offspring would look like? One of my sons has my eyes and my other son has more of his mother‘s eyes? To me that bird has the mask of a greenwing?
That would be an Aleutian Cackling Goose flying with the Cacklers. They do come down to your neck of the woods. https://www.fws.gov/refuge/Humboldt_Bay/wildlife_and_habitat/AleutianCacklingGeese.html