Using the focal point capsules. These are very directional and

need care (practice?) to get on target even when one can see the sound
source.  In fact it was not too easy to focus on the bird on the
nearby high branch.  I did try panning using the focal point capsules
on their own but had little luck.  In particular I tried this to get
some good woodpecker drumming records but by the time I got close to
pointing at a woodpecker it had upped and moved away.

As I have been typing this I realise that, maybe, I should have moved
the potentiometer to a mid point and used a mixture of signals from
the wide stage and focal point capsules for panning/searching. 
However, at the time I was very much focussed on proving the
difference between the wide stage, boundary capsules and the parabolic
dish focal point capsules in an actual field environment.

We live and learn, thank goodness.

Cheers
Tom