Consider the Atlas of the Breeding Birds of Ontario. The current one came out this fall, so apart from the small detail of cost you should easily be able to get a copy.
After that I think you're into general publications that address birds obliquely or non-book papers.
If you haven't already found Algonquin Park's The Raven (formerly weekly in the summer, now 6 issues a year) you may be interested in The Best of the Raven from the Friends of Algonquin Park. While only a few of the articles are about birds, many may give you insights to inform your observations. (I don't know if any of last year's Ravens are still available. Again, not all are about birds.)
Another general book is Eastern Forests in the Peterson series. It's an overview of ecology & habitats.
After that you might want to try your luck chasing the references in the back of eg the Breeding Atlas.
Read on!
