Black Oystercatcher (Haematopus bachmani) behavior and prey selection in intertidal zones on San Juan Island, Washington

Abstract

The Black Oystercatcher (Haematopus bachmani) is a foraging shorebird with a year-long presence in the San Juan Islands that has a specialized beak, used to dislodge prey off rocks in the intertidal zone. Their role as ecological indicators means that shifts in their behavior and diet provide insight into ecosystem health, yet they remain an understudied species. There are no studies focusing on behavior, intertidal composition, such as algae cover, or prey availability of Black Oystercatchers in the San Juan Islands. We conducted a behavioral study using focal animal sampling to understand how Oystercatcher behavior changes across intertidal zones and employed quadrats to assess prey availability using systematic random sampling at two sites, Hunt Property and Third Lagoon on San Juan Island, WA, USA. We found that foraging behavior occurred more frequently at Third Lagoon than at the Hunt Property, likely due to differences in intertidal composition and increased prey availability. Our results indicate that Oystercatcher behavior and foraging success are dependent on intertidal composition and will vary across zones. These findings highlight the need for further research on Black Oystercatchers, their behavior, and prey availability, and may have important implications for management.