I worked on Manitoulin Island for over 10 years and have hunted there for over 20 years. You will have lots of fun and a great opportunity to see more deer than average, however I feel the deer population is gradually declining back to the numbers from the early to mid 1990's. We took 2 deer last year, 5 in 2007, 6 in 2006 for 3-5 hunters as some only come out on days they can get out of work.
There was a large population boom in the early 2000's which saw extra does tags, even farmer tags issued in the more invested areas, such as Robinson Twp. around Gore Bay.
(2-3 tags for farmers prior to season depending on your farm size and location- basically to cull some of the large population).
I think those days are on hold for a while as last year we seen about half the deer we did the last 3-4 years and I hunt in Gore Bay where the population explosion in the early 2000's was tremendous. I think the extra tags allocated the last 6 years or so, the winters (cedar trees- feed) ) and predation have all taken a toll. We did note that some of loss of population may be on the large number of coyote's that can now be heard and evidence seen (seeing or hearing a coyote in the 1980's,1990's was very infrequent), along with almost every cedar tree in the more previously populated areas were chewed bare from 3, sometimes 4 feet to the ground (winter feeding).
I have found that different areas on the Island, as anywhere, have better populations than others. The west end of the Island, also Gore Bay,Kagawong, Billings have always been very good with other areas such as Sandfield, South Bay good as well. This also depends on the property itself (woodlot, swamp or fields) and the weather during that week. I would however, offer this advice from my experience, don't over hunt your property with too many hunters. It is private property and the numbers of hunters during rifle season exceed the local population of residents, so yes, after the first day, the deer get a bit nervous. During the boom years, opening morning can sound like a military shooting range during drill.