Is scarecrows a common or proper noun?

The Word 'scarecrow' is a common noun, a general Word for a human like figure used to keep birds out of gardens and grain fields.

A proper noun is the name of a specific person, place, or thing. A proper noun for the common noun scarecrow is the character Scarecrow for the story/movie "The Wizard of Oz" or Scarecrow Road in Fort Collins, Colorado.