Apache keeps logging errors to /var/log/error.log

Question

I am using name based Virtual hosting on an apache server on Ubuntu 10.0.4

Here is a snippet of one of my sites (in /etc/apache/sites-enabled)

<VirtualHost *:80>
   ServerName example.com
   DocumentRoot /var/www/example

   # CustomLog with format nickname
   LogFormat "%h %l %u %t \"%r\" %>s %b" common
   CustomLog "|/usr/bin/cronolog /var/log/apache2/%Y%m.example.access.log" common

   LogLevel notice
   ErrorLog "|/usr/bin/cronolog /var/log/apache2/%Y%m.example.errors.log"

</VirtualHost>

The access log file is being created in the correct location (with the correct name), but I find that errors are still being logged to /var/log/apache2/error.log

Why is that?