Smart Collection Keyword Problem

i'm having problem smart collections.  bird photography , trying catalog bird images.  created collection set called birds, , created sub-collection sets various species.  smart collections , large job of pulling images proper smart collections based upon keywords i've assigned images.  i'm having problem couple of keywords.

 

i have collection set called ducks, , inside have different duck species set smart collections.  rules smart collection given species simple.  harlequin duck, rule is: keywords, contains words, harlequin duck.  of harlequin duck images correctly pulled smart collection.  if try create smart collection called long-tailed duck using same rule structure, no images show up.  same goes smart collection called wood duck: no images pulled smart collection.  however, if change rule long-tailed duck to: keywords, contains all, long-tailed duck, of images appear in smart collection.  works wood duck collection.  if @ keyword list on right of screen, both of problem keywords there , can see correct number of images next keyword.

 

am doing wrong, or bug?  how can fix problem?  help!

anyone???

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