kingfisher's feet

[Ken Kinman]

I did a little more reading on this subject, and their partially syndactyl foot is not only good for perching, but for digging as well (the long burrows in which kingfishers nest).  Why some kingfishers would completely fuse a two-clawed digging toe into a single-clawed digging toe, I'm not sure.  Possibly they dig into softer substrates and the extra claw is no longer needed.  AND/OR, if the partially-fused double-clawed toe is more easily injured and infected, the full fusion into a single toe would be naturally selected over evolutionary time.  In that sense, it would be "better", in that it would be less deleterious (EVEN IF this fully fused form was slightly less efficient at digging).  I am just speculating though.
  ----Cheers,
         Ken Kinman
P.S.  Since the perching foot of kingfishers was exapted for digging, I think the answer to the original question would be digging (as well as perching).