Looking for spatial data for bird nesting zones in Canada:
Taken from General nesting periods of migratory birds
North American Breeding Bird Survey is what you'll most likely find useful; BBS has two data options.
Migratory Bird Data Center has some more data too.
USFWS Migratory Bird Data Center
Breeding Bird Atlas data - USGS Patuxent Wildlife Research Center
Breeding Bird Survey data - USGS Patuxent Wildlife Research Center
All of these datasets include Canada, but here's Candian specific data: ftp://ftpext.usgs.gov/pub/er/md/laurel/BBS/DataFiles/50-StopData/Pre1997_Canada/ for good measure.