PG levels vs. syslog levels

What is the correlation between PostgreSQL log severity levels and
syslog levels?

Specifically, I have PG (8.1) configured to route messages to syslog and
want to configure syslog to give me a periodic report of all error/worse
events. I configured syslog (syslog-ng) to create hourly files of
error/worse from the PG log data (local2 for me) and generated some
client errors ("select 1 from nonexistent_table;")

As expected, my log shows:
...[23084]: [13-1] ERROR: relation "nonexistent_table" does not exist
...[23084]: [13-2] STATEMENT: select 1 from nonexistent_table;

But my special error log does not. After some testing I have determined
that syslog is seeing this as level "warning".

Thoughts/suggestions?

Cheers,
Steve