It is a plain and simple escapee farm goose.
Why not a Snow goose
1) does not have the black grin on its bills
2) does not have black primaries. it primaries are white and grey
3) bright orange thick feet typical of farm geese
why it is not a Ross's goose
2 and 3 from above
Also it is larger than a Ross's Goose. Ross's are size of brant i.e. tiny geese
Does not have a dark smear on the base of its bill
The vast majority of these Farm geese are Greylag Geese decendants. Just like how dogs were domesticated from Wolfs. Most of these farm geese were from greylags.
There are NO true wild Greylags in Ontario. Any Greylag like goose is an escapee farm goose.
Other domestic bred Goose species which has an escapee in Newcastle for the last 3 years is a Chinese Goose. The Domestic variety are much heavier/meatier than the wild ones.
Warning:
These Escapee Farm geese love to breed with the giant Canada Geese that live here year round. Their offspring come in all shapes and sizes.
just a FYI Western Lake Ontario is a magnet for wierd and unusual escapees. And Lasalle marina is the epicenter for this.
Alot of people keep and breed waterfowl and they do get away. In the last 10 years I have seen the following escapees. Bar-headed Goose 4+, Egyptian Goose 2, Whooper Swan 1, Black Swan 2, Chloe Wigeon 1, Ruddy Shelduck 2, Mandarin Duck 2 and 10+ Barnacle Geese. All species that have never or rarely show up on this continent by themselves.
If you really want to see an impressive Snow Goose Show in 3-5 weeks some of the million+ Greater Snow Goose population will be passing through eastern ontario (cornwall eastward). There one can see 50,000+ in one day. Or drive east of montreal 90mins and see the real show. It is very impressive watching 300,000 Snow geese lift up a dawn to go and feed.