Hello:
High Park is great for birds all year, including the winter. Look for waterfowl in Grenadier Pond if it does not freeze completely. Last year a Wood Duck wintered in the pond. High Park is easily accessed by TTC by Subway at the north (High Park Station) or streetcars at the south (Queen Street line) or on the east side (Carlton 506).
Toronto Islands can be OK over the winter. Accessible by ferry from the docks at the bottom of Bay Street. TTC take the subway to Union and the 510 or 509 streetcar.
The Humber Valley can be accessed from a number of TTC routes and there is a walking path that runs from the Lake all the way to the northern reaches of Toronto. The trail is not cleared of snow or ice. The lower section can be reached from the subway by getting off at Old Mill and walking down Old Mill Road to the park. A map of the trails in the valleys can be down loaded from the City of Toronto web site.
http://www.toronto.ca/cycling/map/index.htm#tcm Sometimes paper copies are available at the MEC store on King Street or bicycle stores in TO. The map should be free.
In the later part of the winter and early spring Colonel Samuel Smith Park has been very good for waterfowl and other birds. It si located on the lake at the end of Kipling Avenue in Etobicoke. TTC is by the Queen Streetcar 501 (Make sure you are on a car going to LongBranch and not a short turn car).
Daryl