Black oystercatcher chick diet and provisioning: 2013 annual report

Robinson, Brian; Phillips, Laura

Black Oystercatchers are important members of intertidal community in Kenai Fjords National Park (KEFJ); they structure the nearshore marine environment through predation, are completely reliant on nearshore marine habitats for breeding and foraging, and are a visible and charismatic bird species that park visitors enjoy viewing. For these reasons, black oystercatchers are vital signs for long-term monitoring at KEFJ. However, data collected during the first few years of monitoring raised questions about possible limitations of our monitoring protocol and identified gaps in our knowledge of the species’ breeding ecology. To address these questions, we initiated a collaborative two-year study, which builds on previous studies of black oystercatcher breeding productivity in Alaska. Our goal was to examine the role of intertidal invertebrates in the diet of black oystercatcher chicks to assess the influence of these prey items on their body condition and survival. In summer 2013, we conducted systematic boat-based surveys of historically known nesting sites in Aialik Bay in KEFJ to locate active black oystercatcher breeding territories. When territorial pairs were found, we searched the area to locate the nest and deployed a Reconyx digital infrared remote-camera near the nest. We monitored 15 nests throughout the breeding season, 40% of which hatched at least one chick. Once eggs hatched, we captured chicks every three days to determine growth rates and body condition and to collect blood plasma for stable isotope analysis of diet. We caught 11 individual chicks repeatedly for a total of 86 captures. We conducted observations of adults with chicks to determine the rate of provisioning and the type and size class of items provisioned. We observed adult black oystercatchers in five territories delivering a wide variety of invertebrate prey to their chicks. Of the 12 chicks that hatched from nests, only two survived to fledge. Apparent nest success of black oystercatchers in this study was comparable to previous studies conducted in KEFJ; however, apparent fledging success was much lower. Next May we will return to Aialik Bay for a second season of fieldwork. We hope to expand our study site to monitor more breeding pairs and deploy additional remote cameras to detect sources of chick mortality during the brood-rearing period in addition to nest monitoring.

Black oystercatcher chick diet and provisioning: 2013 annual report

Series

Collections