In a medium bowl, stir together buckwheat flour, whole wheat flour, sugar, baking powder, baking soda, and salt. Make a well in center of flour mixture; set aside.
In a small bowl, beat egg slightly; stir in buttermilk, oil, and vanilla. Add buttermilk mixture all at once to flour mixture. Stir just until combined but still slightly lumpy. Stir in blueberries.
Heat a lightly greased griddle or heavy skillet over medium heat until a few drops of water sprinkled onto griddle dance across the surface. For each pancake, pour a scant 1/4 cup batter onto hot griddle. Spread the batter into a circle that's about 4 inches in diameter.
Cook over medium heat until pancakes are brown, turning to cook second sides when pancake surfaces are bubbly and edges are slightly dry (1 to 2 minutes per side). Serve immediately or cover loosely with foil and keep warm. Makes 6 (2-pancake) servings.