Great Blue Heron Foraging Behavior and Strike Rate on San Juan Island, WA

Abstract

Pacific Great Blue Herons (Ardea herodias) are large wading birds with ranges throughout many parts of the coastal United States of America, including off of the Washington coast. Although these birds display a variety of feeding behaviors such as standing and walking slowly that are used for catching different prey types, these behaviors are poorly known in the literature. To address this knowledge gap, we wanted to explore how these behaviors vary with tide height, tide phase, strike frequency and success. To compare behaviors in different habitats we chose two study sites, Griffin Bay and False Bay, which were rocky intertidal habitat and sandy tidal flat habitat respectively. Through our focal individual sampling, we found that at both sites Great Blue Herons spent most of their time standing and walking slowly. At Griffin Bay, the herons we observed both struck more per minute and were more successful at catching prey compared to False Bay, potentially due to the larger invertebrate prey availability in the rocky substrate at Griffin Bay. Additionally when looking at tide heights and phases, we found that the herons struck more in the ebb tidal phase but had lower successful strike rates in ebb tide. Our findings suggest a need for further research into the feeding behaviors of the Pacific Great Blue Herons, specifically with regards to different habitat types and feeding success.