The best time to visit Canada for birdwatching is April to early June, or late August to November. The summer months of June and July are mostly unsuitable for birdwatching. During those months you probably won’t find much, even though a few birds can be seen year-round.
Let’s see what kinds of interesting things you can see in August and September in eastern Canada. Let’s start with ducks. Mostly in the summer, in urban areas like Ottawa you’ll mostly just see Mallard, American Black Duck, and Wood Duck. However, when August rolls around, Common Mergansers start to show up.