If the bird you are watching makes a distinctive sound, make careful note of it. Try to repeat it out loud. Field guides often describe songs and call notes as key identifying features. Many bird experts can identify birds by their sounds alone and don't even have to see the bird. It stands for both season of the year and time of day.
Many Canadian birds migrate south for the winter.
Noting the time of day that you observe a bird will often help you decide on its identity. You are more likely to see or hear an owl in the late evening or early morning than at midday. There are many excellent field guides to the Birds of Canada and North America. The following two guides are outstanding, because they have superior illustrations and include maps showing the distribution of each bird species on the same page as the text and illustration. Robins, Chandler, S., Bertell Brunn, and Herbert S. Zim.