DISTRIBUTION AND DISPERSAL IN THE PIPING PLOVER SUSAN M. HAIG • AND LEWIS W. ORING Departmentof Biology,University of North Dakota,Grand Forks, North Dakota58202 USA, and Delta Waterfowland WetlandsResearch Station, Portage la Prairie, Manitoba RIN 3A1, Canada Al•sTRACT.--Individuallymarked Piping Plovers (Charadriusmelodus) were studied from 1981-1987in Manitoba and Minnesotarelative to dispersalpatterns of age and sex classes. Unlike monogamouspasserines, males returned to formerbreeding sites only slightlymore often than females.Dispersal distances did not differ betweenthe sexes.Across North Amer- ica, 24-69% of adultsexhibited breeding-site fidelity, a variability equivalentto that among speciesof migratoryshorebirds. Distribution of Piping Plover habitatacross the speciesrange accountsfor someof this variability: birds used local sitesif they were available,rather than disperselong distances.Similar to most migratory shorebirds,few (1.6-23%)Piping Plover chicksreturned to natal sitesto breed. No differencewas found in return patternsbetween first-yearmales and females,nor in distanceseither sexdispersed from natal sites.First-year birds were found in the vicinity of their natal siteswhen habitatwas available. During winter, birds from the Northern Great Plains and Great Lakeswere seenprimarily in mixed popu- lation flockson the Gulf of Mexico.Piping Ploversfrom Atlanticcoast breeding areas wintered further south on the Atlantic. Received27 November1987, accepted 19 April 1988. DELINEATIONof dispersalpatterns is critical Morse 1980; Myers 1981, 1983; Rappole et al. to understanding many aspectsof a species' 1983; Wilcove and Terborgh 1984). Although population biology and behavior (Horn 1983, the logisticsof a projectof this scaleseem pro- Horn and Rubenstein 1984). Dispersal from a hibitive, a unique situation exists in popula- familiar area may be undertakento avoid close tions of the Piping Plover (Charadriusmelodus). inbreeding or resource competition (Green- This monogamous,migratory shorebird inhab- wood 1980, Shields 1982, Moore and Ali 1984, its isolated sandflats and beachesthroughout Dobsonand Jones1986). Conversely,philopat- central and eastern North America (Haig and ty may lead to the evolutionof cooperativeso- Oring 1985). The limited nature of the species' cial behavior and adaptation to a local environ- distribution and the ease of sighting marked ment (Greenwood 1980, Shields 1982, Waser and birds on beachesprovide an opportunity for Jones1983). Thus, the adaptive significanceof following individuals throughout the year. Re- dispersalis problematic:natural selectionwith- cent interest in raising Piping Plover popula- in a populationseemingly mitigates against long tions to former levels spurred development of distancedispersal, but only disperserscan found researchin most of the species'major breeding new populations (Horn 1983, Swingland 1983, areas, and further increased the chances that Moore and Ali 1984, Liberg and von Schantz marked birds would be resighted. We report 1985). Piping Plover dispersalpatterns throughout the Most characterizationsof species' dispersal annual cycle, and suggestthat distribution of patternsare basedon investigationsof a single habitat may explain some of the variability in local population during limited periods in the return patterns exhibited among the sexes,age annual cycle.For migratorybirds, which spend groups,and differentpopulations of the species. lessthan 50% of their annual cycle at breeding sites, it has become increasingly apparent that METHODS interactions across seasons must be taken into We studiedPiping Ploversin southeasternMani- account to better understand the effects of dis- toba from 1981-1986, and in northwestern Minnesota persalon socialsystems (Keast and Morton 1980; from 1985-1987 (Haig and Oring 1987, 1988a,b). In Manitoba,breeding birds (50 males,47 females)and their chicks(n = 122) from Lake Manitoba, West Shoal • Present address:Department of Zoological Re- Lake, and Grand Marais on Lake Winnipeg (locations search,National ZoologicalPark, SmithsonianInsti- describedin Haig and Oring 1988b)were captured tution, Washington,D.C. 20008 USA. in mistnests and givenunique combinations of color 630 The Auk 105: 630-638. October 1988 October1988] PipingPlover Dispersal Patterns 631 bands.All Piping Ploversbanded after 1983were also given international leg flags(Myers et al. 1983,Haig et al. 1988). Piping Plovers were sexedas described by Haig and Oring (1988b). From 1982-1986, distribution of the 100-120 Piping Ploversbreeding in Manitoba and identificationof markedbirds were determined through province-wide censusesand surveys(Haig 1985,1987a). Weekly cen- suses were carried out at 3 sites on Lake Manitoba: StonyBeach, Twin LakesBeach, and ClandeboyeBay, from 1982-1985; and at West Shoal Lake from 1984- 1985.Grand Marais was censusedevery 3 weeksfrom 1983-1985, and twice in 1986. Lake Manitoba, West Shoal Lake, and Lake Winnipeg sites were censused at leastonce in 1987by the ManitobaDepartment of Natural Resources(W. Koonz pets. comm.).The num- Fig. 1. Distributionof Piping Ploverbreeding and ber of adults, nests, and chicks was recorded, as well winter areas as of 1987. as identification of marked birds and their mates. In Minnesota, Piping Plovers primarily bred at 4 sites on the southwestern barrier islands of Lake of surveysand censusesvaried among researchers,we the Woods (Wiens 1986). Research begun in 1982 includedonly the following in further analyses:iden- (Wiens1986) was continued by the authorsfrom 1985- tificationof sitesthat Piping Ploversused throughout 1987(Haig and Oring 1987).From 1982-1986,53 adults the year,adult populationsizes, and identificationof and 110 chickswere individually marked with color marked birds. Currently, most major breeding sites bandsand, after 1984,with internationalflags. In 1985- are censusedat leastannually (Dyer et al. 1987,Haig 1987, 31-42 adults and their chicks were censused et al. 1988). Major Gulf of Mexico sites and a few approximatelyevery 3 weeks during the breeding Atlantic coast winter sites are frequently censused season.Censuses in Minnesota used methodology from August-April (Johnson 1987, T. Amos pets. similar to that in Manitoba. comm., T. Eubanks pets. comm., J. Nicholls pets. The presenceof researchersat major Piping Plover comm.,J. Toups pets. comm.). breeding sites in the surrounding area enhanced We define breedingdispersal as movementof breed- monitoring marked birds that dispersedto Michigan ing adults between breeding seasons,whereas breed- (Pike 1985),Wisconsin (S. Mattesonpets. comm.), On- ing-sitefidelity is the return of a breeding bird to its tario (L. Heyems pets. comm.),central North Dakota formerbreeding site (e.g. Stony Beach, Grand Marais) (Prindiville 1986,Mayer and Ryan 1986),or Nebraska in successiveyears. Natal dispersal is dispersal of young (Nebraska Game and Parks Commission 1978-1987). prior to first breeding, natalphilopatry occurs when a In addition, marked birds were recordedduring cen- first-yearbird returnsto its hatchsite to breed. Winter susesat major breeding sitesin Saskatchewanin 1984 dispersalis the movement of adults and fledglings and 1985 (Harris et al. 1984, Haig unpubl. data); in from breeding/hatch sitesto winter sites. South Dakota in 1986 (Schwalbach et al. 1986); and in Montana during 1986-1987(Montana Piping Plov- RESULTS er Recovery Committee 1986, A. Dood pets. comm.). Atlantic coastsites were heavily censusedduring the BreedingdispersaL--Piping Plover population past 5 years (Dyer et al. 1987). Dispersal data from Piping Plovers on Long Island, New York (Wilcox studiesdemonstrate a high degreeof variability 1959), are presentedfor comparisonbetween inland in site fidelity among study sites (Table 1). In and Atlantic birds. 5 of 8 studies, over 50% of adults returned to We determined Piping Plover distribution (Fig. 1) former breeding sites. In most studies, breed- by direct censuses,and coordinationof surveysand ing-site fidelity of males and femaleswas not censuses carried out in North America between 1982 reported, but in Manitoba, returns of males and and 1987 (Haig 1985, 1986, 1987b; Haig and Oring femalesdid not differ significantly(x 2 = 2.23, 1985;Dyer et al. 1987;Haig et al. 1988).In 1982,we 1 df, NS; Haig and Oring 1988b).Most marked establishedan information clearinghouseat Delta Waterfowl and Wetlands Research Station that re- breeding birds seen in subsequentyears (Fig. questedsightings of marked Piping Plovers, census 2) returned to former breeding sites in Min- data,and distribution information from over 700 gov- nesotaand New York. Manitobabreeding birds, ernment agencies,museums, universities, biologists, however, returned to the general area (i.e. and conservationgroups, throughout the Americas southern Manitoba), but frequently changed and the Caribbean. Although data collected during breeding sites. 632 HAIG AND ORINIG [Auk, Vol. 105 TABLE1. Breeding-sitefidelity and natal philoparry in Piping Plovers. Nest- ing n Fledged n Years adults return chicks return Focal of Study location banded (%) banded (%) sites study Source Southern Manitoba 65 44 (67.7) 90 5 (5.5)a 5 4 This study 11 (12.2)b Cape Cod, Massachu- 16 1! (68.9) 28 0 (0.0)' 12 3 Maclvor et al. setts 12 (42.9)b 1987 WaugoshancePt., Mich- 16 9 (56.3) 35 1 (2.9)' 1-10 11 Pike 1985,pers. igan 8 (2.9)• comm. Lake of the Woods, 47 32 (68.0) 70 15 (2!.0) 4 3 Wiens !986 Minnesota Long Island, New York !,!73 288 (24.6) 979 34 (3.4)' 3 20 Wilcox 1959 47 (4.8)b Chain