pg_ctl and stderr

On 7.4.6 and earlier, we use apache's log rotation program as follows:

pg_ctl start | rotatelogs ...

If we have a configuration failure, say a bad parameter in postgresql.conf,
we often don't quickly notice because it goes to stdout (into the log).

It'd be nice if it went to stderr as well so we could see it without having
to search the log, but that wouldn't work if we wanted to capture stderr in
the logs (do normal ERROR messages go to stderr?).

Just curious how folks make pg_ctl start-up failures obvious while also
piping to apache rotatelogs?

Ed