Common Redpolls are circumpolar breeders: in Ontario they breed chiefly in the Hudson Bay Lowlands.
Great numbers invade southern Ontario during some winters, often followed by one to three winters with few or none.
During invasions they are often attracted to “distlefink” feeders (with niger seed), even in city backyards.
They frequently associate with Pine Siskins and American Goldfinches at these feeders, or on seed-laden birch trees as well as in fields of pigweeds.
These winter finches are about the size of goldfinches or chickadees, generally grayish-white heavily streaked with dusky.
The bright red cap when visible will easily identify them from all but the Hoary Redpoll.
In fast moving flocks they may often be distinguished by their characteristic wooden “cha-cha-cha” call from the similar Pine Siskins which have a more buzzy call note.
Both are heavily streaked, bouncy, little birds and can be difficult to separate in poor seeing conditions (when back-lighted or in rapid flight.)
The more pointed bill and yellow wing flashes will help to identify the siskins in such conditions.