Full Idea
It seems that the dominant "component" of natural kind words is the extension. The referential factor does almost all the work, and natural kind terms resemble names.
Gist of Idea
Like names, natural kind terms have their meaning fixed by extension and reference
Source
Hilary Putnam (Representation and Reality [1988], §3 p.49)
Book Reference
Putnam,Hilary: 'Representation and Reality' [MIT 1992], p.49
A Reaction
My concept of 'tiger' does not mainly consist of the tigers. Does the concept contract as the tiger population dwindles? Prototypes, exemplars etc. See 'Concepts'