Nest Success and Habitat Selection of the Semipalmated Plover on Akimiski Island, Nunavut

—We studied nest site selection by Semipalmated Plovers (Charadrius semipalmatus) to compare microhabitat characteristics at nest and random sites, and to compare successful and unsuccessful nests on the northern shore of Akimiski Island, Nunavut, during 2002. Nesting birds selected sites with more pebbles and less vegetative cover than randomly available in the environment. Nest sites also had smaller percentage of bare mud than random sites. Plovers selected sites within 100 m of Arctic Terns (Sterna paradisaea) more often than expected based on the distribution of random sites in the study area. Twenty-three of 41 (56%) nests hatched successfully. None of the microhabitat features that we measured predicted nest success. All 10 nests near the colony of Arctic Terns hatched, suggesting that interspecific associations are more reliable than habitat features for predicting nest success. Received 10 May 2003, accepted 25 September 2003. Nest site selection in shorebirds has important consequences for their survival and reproduction (Dyrcz et al. 1981, Espie et al. 1996, Powell 2001). Although the behavioral mechanisms of selection are poorly understood, the outcome is a nonrandom distribution of nests among available sites (Cody 1985, Lauro and Nol 1995). Nest predation may be the most important selective pressure affecting nest success (Lauro and Nol 1995, Lloyd et al. 2000). If microhabitat differences exist between successful and unsuccessful sites, natural selection may modify adaptive strategies (e.g., which habitats are used for nesting) to reduce predation risk. While other factors such as access to food for adults and/ or young (Lauro and Nol 1995) and interspecific interactions (Dyrcz et al. 1981, Burger 1987, Powell 2001), influence nest site selection, predation risk is more important in the immediate vicinity of the nest. This general principle is the basis for numerous studies attempting to associate microhabitat structures with used and available sites, as well as successful and unsuccessful sites (Flemming et al. 1992, Espie et al. 1996, Powell 2001). The Semipalmated Plover (Charadrius semipalmatus) is a common shorebird of open habitats in the Arctic and sub-Arctic regions of North America (Nol and Blanken 1999). 1 Dept. of Biology, Trent Univ., Peterborough, ON K9J 7B8, Canada. 2 Wildlife Research and Development Section, Ontario Ministry of Natural Resources, 300 Water St., 3rd Floor North, Peterborough, ON K9J 8M5, Canada. 3 Corresponding author; e-mail: [email protected] There are numerous accounts of the breeding biology of this species (Sullivan Blanken and Nol 1998, Nol and Blanken 1999), but little quantitative information is available on microhabitat characteristics of their nest sites (Nol and Blanken 1999). This species and other members of the genus rely on crypsis to enhance nest success. Some authors have argued that objects near the nest increase crypsis (e.g., Graul 1973, Lloyd et al. 2000). Therefore, we might expect that features around the nest and variation in these features would be related to variation in reproductive success. Hence, we compared physical and vegetation characteristics of Semipalmated Plover nest sites to random sites, and of successful and unsuccessful nests on Akimiski Island, Nunavut, Canada.