MassLep - join
Butterfly watchers from around Massachusetts send messages listing the butterflies they see, describing butterfly behavior, posing questions, and answering them. Joining this group is a great way to find out what's flying and to get to know others who share your interests!.
Low activity, 187 members

Central Illinois Birding - join
CILB is for area birders to communicate using email and the web. Questions, identification help, and topics regarding conservation are welcome. Significant mammal sightings are also welcomed. Please list the county in the subject line for sightings and sign posts with first and last name.
Low activity, 99 members

rec.birds - join
Hobbyists interested in bird watching.
Medium activity, 632 subscribers, Usenet