Mate, Site, and Territory Fidelity in Piping Plovers

Abstract

-Breeding-site fidelity, territory retention, and mate fidelity were examined in a color-banded population of monogamous Piping Plovers (Charadrius melodus) breeding at five focal sites in southern Manitoba from 1981 to 1986. Frequent nest destruction by predators and storms provided numerous opportunities for birds to change mates and territories during and among breeding seasons. Between years approximately 70% of surviving adults were site faithful. Males did not return significantly more often than females, and both sexes returned regardless of previous reproductive success. Although former mates were present in subsequent years, 30 of 37 birds changed mates. Birds that changed mates from the previous year and whose mates were present in subsequent years had experienced poorer hatching success the previous season than those that retained mates. Birds that retained mates did not improve their reproductive success over the previous year. After nest destruction during the breeding season, most adults kept mates (34/52 pairs) but changed territories. Birds changed territories significantly more often, and moved significantly farther, following nest destruction by storm than following predation. Birds that retained mates during the breeding season fledged more chicks than those that changed. Received 5 June 1987, accepted 19 November 1987. IDENTIFICATION of individual behavioral phenotypes and subpopulation demographic characteristics exposes a vast amount of variation in organisms with even the most rigid social systems (Bekoff 1977, Oring et al. 1983, Mock 1985, Beissinger and Snyder 1987). In birds more than 90% of the species exhibit a primarily monogamous mating system (Lack 1968, Oring 1982). Until recently, monogamy generated little interest, largely because of a belief that exceptional mating systems had more potential for contributing to an understanding of the evolution of avian social systems. Even in monogamous species mate choice and re-pairing occur throughout an individual's lifetime, and present many options for variation in this social system (Ford 1983, Rowley 1983, Wickler and Seibt 1983, Anderson 1985, Mock and Gowaty 1985, Oring and Sayler in press). In this paper we report envirorfmental and social factors that can lead to variability in mate retention, site fidelity, territory retention, and reproductive success in the monogamous Piping Plover (Charadrius melodus). Piping Plovers are biparental, territorial 1 Present address: Department of Zoological Research, National Zoological Park, Smithsonian Institution, Washington, D.C. 20008 USA. shorebirds that often breed repeatedly in the same area (Wilcox 1959, Cairns 1982, Wiens 1986, Haig 1987a). Throughout their breeding range Piping Plovers nest in highly ephemeral beach habitat that is regularly washed out or otherwise altered (Haig et al. 1988). Previous studies of monogamous shorebirds indicate that mate retention and site fidelity may produce greater relative reproductive success (e.g. Soikkeli 1970, Hale and Ashcroft 1982, Lessells 1984, Gratto et al. 1985). Therefore, one might predict that Piping Plovers exhibit similar patterns. The dynamic environment they inhabit, however, provides occasions for birds to reassess mates, territories, and breeding sites within and between years. STUDY AREA AND METHODS The study was conducted from 1982 to 1985 in Manitoba (Fig. 1). One hundred to 120 Piping Plovers bred annually in Manitoba on 10 sites in the southern portion of the province (Haig 1985, 1987b). We selected study areas from among these sites. Stony Beach (50?14'N, 987'W) is a 2-km stretch of narrow (x? beach width = 11.5 m), sandy, pebbled beach located 13 km east of Delta Waterfowl and Wetlands Research Station on a beach ridge separating the Delta Marsh from Lake Manitoba. Three to 5 pairs bred there in 1982-1985. Clandeboye Bay (50?15'N, 98?6'W) is located 2.2 km 268 The Auk 105: 268-277. April 1988 This content downloaded from 207.46.13.114 on Thu, 26 May 2016 06:17:29 UTC All use subject to http://about.jstor.org/terms April 1988] Piping Plover Mate and Site Fidelity 269