This is intended to be a comprehensive list of all publicly available groups for reporting, discussion and identification of Ontario's natural history. Groups for a slightly broader area (e.g. the Great Lakes Region) can also be included.
Be sure to read and follow all rules and instructions provided for each group. In particular, note that some of these are intended for sharing of notable sightings, and not necessarily for discussion, identification or other purposes.
Field Naturalists of Ontario Facebook: General discussion of Ontario nature.
Muskoka Bird Board: Despite the name, a board for general nature sightings in Muskoka and nearby areas.
Simcoe Nature Board: Simcoe County. Birds and general nature sightings.
Ontbirds: The main listserv for rare birds across Ontario.
Ontario Birds Facebook: A large and growing group for everything bird-related in Ontario.
Toronto and Southern Ontario Birding: A large forum for birding and general nature in the GTA and across Ontario.
NWOBirds: Northwestern Ontario bird reports. You must request membership to view or post.
Stratbirds: Stratford reports. You might have to request membership to post, but not to view.
Guelph/Cambridge/KW Birding Forum: Birding in Wellington and Waterloo countys.
Wellbirds: Birds in Guelph and Wellington County. The only way to view posts is by requesting to receive the emails.
Waterloo Region Birds Facebook: Rarities and discussion in Waterloo Region.
Brantbirds: Birds in Brant County.
Hamiltonbirds: Notable birds in the Hamilton Study Area, a large area extending out to Mississauga, Guelph, Cambridge and well into Niagara Region.
WEPBirds: Birds in Essex County including Pelee and Windsor.
ABA Great Lakes News and Discussion Facebook: Birding discussion for the whole Great Lakes area.
Ontario Butterflies: Butterflies across Ontario, primarily used for reporting rare species.
OntOdes: Dragonflies and damselflies across Ontario, primarily used for reporting rare species.
Hamilton Butterflies and Dragonflies Google Group: Sightings in the Hamilton Study Area (roughly Mississauga to Guelph to Brantford to Grimsby).
Ontario Insects and Arachnids Facebook: Discussion and identfication of any Ontario insects.
Northeast Odonata Facebook: Discussion and identification for dragonflies and damselflies in Northeastern North America.
Ontario Reptile and Amphibian Atlas Facebook: A large group for discussion of the Atlas and herps in general.
Field Botanists of Ontario Facebook: Plant discussion and identification in Ontario.