The Common Merganser is North America's largest cavity-nesting duck, and hens remain attentive to the youngsters after they leave the nest. Females squire their very young chicks about like avian water taxis, although only a few of the tiny birds can fit on her back at a time. Thus, the riders change constantly as chicks clamber aboard and shove current passengers into the drink. Riding atop mom makes chicks safer from underwater predators such as pike and snapping turtles - major threats to ducklings.