I returned to Petrie Island this morning with the sole intention of counting Blue Dashers. I counted 21 altogether, 18 males and 3 females (or immature males). The males all preferred to perch on a stick or piece of vegetation above the water, while all three females were found in the vegetation next to the path. The males were also quite aggressive, chasing larger dragonflies that ventured into their space; there were probably more than 18, but I only counted the maximum number I could see at any time at various spots along the trail.