Mother Mallard builds nest and hatches a number of ducklings (all with human names). They then face the perils of nature. I remember one disappearing from the nest. (fox).  The smallest one and last in swimming line suddenly disappears underwater (snapping turtle).  The book is probably from the 50’s.  It is a realistic story and I had a love/hate relationship with it.  I threw it out when I was in college (too bad).  I would like to find it again.