PostGopher and BirdSend
To make the changes necessary to integrate with BirdSend will require a lot of coding that will make the plugin too big for the normal, simple installation and activation procedure in WordPress - which limits plugins to 2k bytes for this to happen.
So - adding a huge amount of code for just BirdSend - for just one or 2 customers - will affect ALL our customers and all future customers. Hence we are loath to do it.
Amost all other autoresponder services allow anonymous HTML requests - which BirdSend doesn't. So we have programmed for the vast majority of customers AND autoresponders.
We're really sorry we can't help in this particular instance.