If fresh blueberries aren't in season, you can use frozen berries. There is no need to thaw the berries before folding them into the batter. Substitute other berries, including raspberries, strawberries, or blackberries for the blueberries.
We've strained the syrup for a smooth, pourable consistency. You may prefer to skip the straining step for a more rustic texture, similar to that of a fruit topping. In that case, simply add the maple syrup once the blueberries and their liquid have a soft, jam-like texture.