Meeting Abstract
The amphipod, Corophium volutator, is the primary prey for Semipalmated Sandpipers in the upper Bay of Fundy during fall migration. In the upper Bay, Corophium populations have two barely overlapping generations a year. The summer generation, born in May and reproducing in late August, provides the majority of the food for the sandpipers. Size-selective predation by the birds ameliorates inter-generational competition between the adults and juvenile Corophium. The preferential removal of large, post-reproductive Corophium by sandpipers can be viewed as resource management, increasing the probability that the juvenile Corophium released in August will overwinter to give rise to the next summer generation. In the lower Bay of Fundy, Corophium display a single generation each year with reproduction beginning in July. The lower Bay hosts few shorebirds during the fall migration. However, the lower Bay has significantly colder water than the upper Bay. The differences in Corophium life history within the Bay of Fundy could be explained by the warmer upper Bay of water temperatures promoting faster growth, permitting two generations a year. Alternatively, the sandpiper-Corophium interaction could be viewed as the result of coevolution between predator and prey. To tease apart these hypotheses, I documented the life history of Corophium along the central Maine coast at Lowes Cove, Walpole, ME. The water temperature at Lowes Cove is relatively warm, like upper Bay waters. Shorebird use at Lowes Cove and most intertidal mudflats in central Maine is sparse. Corophium at Lowes Cove display the two generations per year pattern seen in the upper Bay of Fundy, rejecting the hypothesis that shorebird predation drives the life history of Corophium in the upper Bay.
