Factors Affecting Piping Plover Chick Survival in Different Brood-Rearing Habitats

Abstract

The decline of piping plover (Charadrius melodus) populations and subsequent listing as a threatened species has been attributed, in part, to low chick survival. During 1988-90, we observed piping plover chicks daily to evaluate hypotheses of differential food resources, predation, and disturbance explaining differences in chick survival in 3 habitats on Assateague Island National Seashore (AINS), Maryland. Chicks reared on the bay beach and island interior had higher daily survival rates (0.97, 0.99 vs. 0.87; P < 0.001), higher foraging rates (13.3, 10.8 vs. 5.9 attempts/min; P < 0.001), and spent more time foraging (76, 80 vs. 37%, P < 0.004) than chicks reared on the ocean beach. Terrestrial arthropod abundance on the bay beach and island interior was greater than on the ocean beach in 5 of 6 cases (P < 0.01). Amphipods, however, were more abundant on ocean beaches than in bay and island interior habitats each year (P ≤ 0.03). Chicks 4-5 days old that were reared on the bay beach or island interior habitats were heavier than those reared on the ocean beach (8.5, 7.8 vs. 6.5 g; P < 0.01). Overall disturbance rates did not differ among habitats (behavioral observations; P = 0.29). The number of predator trails did not differ among the 3 habitats (P = 0.2). Red fox (Vulpes vulpes) trails were more numerous in the island interior and ocean beach (P < 0.001), ghost crab (Ocypode quadrata) burrows were more numerous on ocean beach (P < 0.001), and gull (Larus spp.) and raccoon (Procyon lotor) trails were more numerous on bay beach (P < 0.001 and P = 0.001, respectively). Piping plover chicks moved from ocean beach nest sites to the bay beach and island interior along ephemeral, vegetation-free paths created during winter storms by waves surging across the island. These paths should be maintained to enable piping plover chicks to move to the island interior and bay habitats where chick survival is greatest. Preserving access to high quality brood-rearing habitat will ensure reproductive rates that will sustain the local population and contribute to the species' recovery.