For the beak: Stand an orange gumdrop on its base. Snip with scissors straight down about three-quarters of the way through to make the mouth. Trim around all sides of the gumdrop to decrease the size and shape into a tapered beak. Repeat to make remaining beaks.
For the duck: Make a 1/2-inch ball with some of the yellow fondant for the head. Attach the beak to the head by inserting it into the ball and reshaping around it. Form the remaining fondant into a teardrop shape. Dab the bottom of the head with water and attach to the side of the teardrop, toward the big end. Repeat to make remaining ducks.
For the eyes: Dip a skewer in the melted chocolate and make 2 small dots on each duck head for eyes. Set aside.
To assemble: Frost the cupcakes with the buttercream. Place the avocado-tinted frosting in a pastry bag with a #235 Wilton fuzzy tip. Hold the bag straight up, with the tip 1/8 inch above the surface. Squeeze to form grass on the top of the cupcake, and then stop squeezing and pull the pastry bag up, making grass blades about 1/2-inch long. Repeat around the edges of the cupcake to form a ring of grass. Repeat with remaining cupcakes.
Sprinkle the center of the cupcakes with blue sanding sugar to make the pond. Place the ducks in the center and press gently to adhere.