I don't think it's a case of either/or.  'Natural drive' frequently culminates as a pleasurable sensation (or relief) of fulfilling a compelling urge.  For ducks, and for humans.  Neurologically we're not wired all that different.  And you're in one of the best places on the continent to scratch a 'biological itch'.  Wood frogs should be out now.  Listen for the sound of low chuckling around even temporary bodies of water, then moves slowly and look carefully in the grass.  Happy springtime to you!