Auto vacuum

I asked questions about auto vacuum earlier. As I said in my earlier
email, when I select autovacuum the system responds that it's "on."
Some here told me when I asked the questions before that I should see
log entries for it when it "kicks off." In postgresql.conf, it says
that the log_destination is 'stderr." Then it redirects "stderr" to
a file named 'postgresql -%Y-%m-%d_%H%M%S.log' in a directory called
pg_log. I don't see any references to auto-vacuum in the log. What
would the references look like? Is there a parameter I need to set
in order to make in put auto vacuum entries in the log?
client_min_messages is set to "notice." log_min_messages is set to
"info." log_error_verbosity is set to "default."
log_min_error_statement is set to "warning."
log_min_duration_statement is set to 1000

Thanks

Carol