Red Knot ( Calidris canutus rufa ) prey selection in Virginia during spring migration

Understanding which prey birds select plays a valuable role in conservation planning, especially for imperiled species. Abundant prey at staging sites during migration is key to survival and breeding success. We determined prey selection of Red Knots (Calidris canutus rufa) on Virginia’s barrier islands, one of the largest spring staging sites for this species. To quantify which prey was available to foraging Red Knots, we collected substrate core samples containing prey on sand and peat substrates in May 2017–2019. To confirm which prey Red Knots consumed, we collected feces during the same period and identified prey using DNA metabarcoding. We then tested for prey selectivity of Red Knots using network null modeling in the econullnetr package in R. Red Knots consumed clams, mussels, crustaceans, and insects. Clams were the most abundant prey in sand substrates while crustaceans were the most abundant prey in peat substrates. Red Knots selected bivalves (i.e., clams and mussels) over non-bivalve prey, though non-bivalve prey were still abundant and consumed. Coastal conservation practices in the Western Mid-Atlantic staging region should seek to promote natural barrier island migration processes and to avoid stabilization when possible. Natural migration dynamics of barrier islands lead to the availability of both sand and peat substrates colonized by many prey species and foraged on heavily by staging Red Knots.