Foraging Behavior and Success in Great Blue Herons (Ardea herodias) at False Bay, San Juan Island

Abstract

The great blue heron (Ardea herodias) is a widely distributed marine bird found throughout North America, residing in large colonies. Resident colonies wade in salty and brackish systems, foraging for smaller fish and invertebrates. They are visual hunters, relying on shallow tides to stalk and strike prey. Over the course of three days, we monitored the local colony at False Bay, WA, recording foraging behavior as well as individual strike rates and success. Our results indicate that herons do not engage in cooperative foraging and prefer to feed solitarily. We found that the strike rate was higher in solitary individuals, but success was even between both groups. We suggest this is due to higher intraspecific competition when tidal heights limit foraging opportunities. The energy content of their specific prey may also factor into strike rate, increasing the rate as nutritional density decreases. Great blue heron foraging behavior impacts the estuary through the top-down trophic control, managing the abundance of primary consumers and allowing for eelgrass growth. Lastly, further research is needed to determine whether the False Bay population is a part of a special concern subspecies, A. h. fannini. These findings support the conservation efforts focusing on False Bay and the importance of foraging behavior of great blue herons.