This Haiku uses a 'zooming out' method if I may say so. "a red butterfly" "sailing" on the invisible or echoing "wind" to the vast "first day of spring" which could expand into many different perceptions for different people.
~ "butterfly" is an active and self-vident spring kigo and Keith knows that too! But "first day" makes the aesthetic and poetic necessity of the "spring" to be explicitly mentioned in the last line.
A careless observer may feel that the "spring" is already implicit in the "butterfly", but here the explicit closure on the word "spring" is necessary for structural reasons too of the essential spirit of this Haiku. The Haiku invokes a moment of awareness of a new spring.
~ "butterfly" is an active and self-vident spring kigo and Keith knows that too! But "first day" makes the aesthetic and poetic necessity of the "spring" to be explicitly mentioned in the last line.
A careless observer may feel that the "spring" is already implicit in the "butterfly", but here the explicit closure on the word "spring" is necessary for structural reasons too of the essential spirit of this Haiku. The Haiku invokes a moment of awareness of a new spring.