Mayfly Madness: Blue Winged Olives and March Browns

Red-winged Blackbird

One of the surest signs of a strong mayfly hatch is the sight of birds swooping low over the water, picking off insects mid-flight. This is often a giveaway that Blue Winged Olives (BWOs) or March Browns are emerging.

BWOs start hatching in early spring on humid, overcast, or rainy days. Their nymphs build up gases under their exoskeletons, which help them rise to the surface before breaking free as duns. These small mayflies provide consistent dry fly opportunities, especially on slow, glassy runs where trout sip them with precision.

Following the BWO hatch, March Browns make their grand entrance, typically just after lunch. Their larger size (often in the 12-14 range) makes them a favorite among both fish and anglers. After the duns hatch, thick clouds of spinners gather later in the afternoon, providing another window of opportunity to fool rising trout. Fishing a well-placed parachute pattern in brown hues can be highly effective and easy to track on the water.