DISTRIBUTION AND DISPERSAL IN THE PIPING

SUSAN M. HAIG • AND LEWIS W. ORING Departmentof Biology,University of ,Grand Forks, North Dakota58202 USA, and Delta Waterfowland WetlandsResearch Station, Portage la Prairie, Manitoba RIN 3A1,

Al•sTRACT.--Individuallymarked Piping (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: 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 and Great Lakeswere seenprimarily in mixed popu- lation flockson the .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 (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 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 • Present address:Department of Zoological Re- Lake, and Grand Marais on (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 to its tario (L. Heyems pets. comm.),central North Dakota formerbreeding site (e.g. Stony , 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. 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 , 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 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 . 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 of Lakes,North 1!! 32 (55.2) !23 7 (6.0) 7 2 Mayer & Ryan Dakota !986 Cadden Beach, Nova !9 7 (36.8) 39-57 ! (!.6-2.6) ! 2 Cairns 1982 Scotia Big Quill Lake,Sas- !4 6 (42.0) !2 ! (8.3) ! 2 Whyte (!985) katchewan

Total !,46! 429 (29.4) !,376-!,394 64 (4.7)a !02 (7.3-7.4) •

Return to natal site. Return to local area (including natal site). In all cases,except Whyte 1984,local siteswere surveyedin addition to focal sites.

Dispersal distances of Piping Plovers that wintering areasfor the entire year (S. Haig un- chosenew breeding sites varied considerably pubL data,T. Eubankspers. comm.). Few Piping from former sites(Table 2). In New York, only Plover chicks from any study area returned to 3 adults that returned to Long Island did not natal sitesto breed (Table 1). Many non-philo- settle on former sites. These birds bred 9-26 km pattic chickssettled in areassurrounding their from previousnests (Wilcox 1959).Piping Plo- natal sites in Manitoba, New York, and Min- vers in Manitoba frequently moved between nesota.There was no sexbias among philopatric Lake Manitoba and West Shoal Lake during the birds in New York (16 males vs. 18 females breedingseason (Haig and Oring 1988b)as well returned; Wilcox 1959) and Manitoba (2 males as between years. Only 1 adult moved from vs. 2 females vs. 1 unknown-sex bird returned). these areas to Grand Marais. Manitoba birds were Further, there was no significant sex bias in never seen in Minnesota. However, adults from distancesdispersed by birds hatched in Mani- Lake of the Woods, Minnesota, moved into tobaor New York (Table3). On average,females Manitoba in 1984, 1985, 1986, and 1987 (n = 4). resightedin New York dispersed12.8 km (SD Current data are limited, but do not indicate a = 24.5, n = 25) from natal sites, while males significantsex bias in distancesdispersed. In were found approximately8.6 km (SD = 16, n New York, 2 females dispersed25.9 and 18.3 = 21) from natal sites.In Manitoba, all returning km from previousnest sites,while 1 male bred first-yearbirds bred at West Shoal Lake after 9.1 km from its former nest (Wilcox 1959). In hatchingat a site on Lake Winnipeg or Lake Manitoba, resighted males that were not site- Manitoba(Table 3). Similarly, LongIsland birds faithful dispersed further than females, al- convergedon Shinnecock(Wilcox 1959). Re- though the differencewas not significant(œ = sighted first-year birds that did not return to 35 kin, SD = 14.5, n = 8 for males vs. œ = 26 Lake of the Woods moved north to Manitoba, kin, SD = 9.8, n = 10 for females) (Mann-Whit- settling at West Shoal Lake and Grand Marais ney U' = 29, NS). on Lake Winnipeg. Natal dispersaL--PipingPlovers frequently All non-philopatricLake-of-the-Woods chicks bred the first year after hatch (Haig and Oring dispersedover 200 km from hatch sites(Fig. 2). 1988b), and only a few (n = 6) remained in In Manitoba and New York, more birds bred at October1988] PipingPlover Dispersal Patterns 633

NATAL PHILOPATRY BREEDING SITE FIDELITY a site 1.1-10 km from their natal site than re- 908o f MINNESOTAn:21 turned to natal sites. Furthermore, 50.9% (n = 12) of Manitoba chicks and 24.5% (n = 53) of New York chicksobserved the next year were found t0. t-t00 km from natalsites. The greatest distancedispersed (approximately 1,500 kin) was CC by a male that hatched at West Shoal Lake in 1985and was capturedin a mist net the follow- 7o MANITOBA ing August at Long Point, Lake Erie. • 60 n=70 Winter dispersaL--Ninety-onewinter sight- ings of Piping Plovers banded during the breeding seasonindicate that inland breeding birdswintered primarily on the Gulf of Mexico. Birds that bred along the Atlantic coastwin- tered further southalong the Atlantic (Fig. 3). • n-53 A few birds from Manitoba, North Dakota, and Michigan were sightedalong the Atlantic coast, but there was only t sighting of an Atlantic breeding bird wintering on the Gulf. Marked birds from inland breeding areas wintered throughoutthe Gull and did not demonstrate significantgeographic differentiation by breed- ing site location: Piping Plovers from North Fig. 2. Comparisonof distancesdispersed from Dakota, Minnesota, Michigan, and Manitoba natalsites in Piping Plover chicksresighted their sec- occurred in both and Texas. ond year (left column)and distancesadults dispersed betweenbreeding sites in successiveyears (right col- DISCUSSION umn). Distance intervals (km) on bars are: 0-1.0, 1.1- 10.0, 10.1-100.0, 100.1-1,000.0, 1,000.1-10,000.0. Natal dispersaL--Recentconsideration of the Sources:this study,Wilcox 1959,Wiens 1986. costsand benefitsof juvenile dispersalcontrasts possiblenegative genetic effectswith somatic

TABLE2. Dispersalof breedingPiping Ploversbetween years.'

Sexb Km State or dis- province Breeding site 1 Breedingsite 2 M F U persed Manitoba ClandeboyeBay, Lake Manitoba Stony Beach,Lake Manitoba 1 3 ClandeboyeBay, Lake Manitoba West Shoal Lake 3 3 32 Stony Beach,Lake Manitoba Twin Lakes Beach, Lake Manitoba ! 15 S. West Shoal Lake N. West Shoal Lake 8 8 West Shoal Lake ClandeboyeBay, Lake Manitoba 2 3 32 West Shoal Lake Grand Marais,Lake Winnipeg ! 70 West Shoal Lake Twin LakesBeach, Lake Winnipeg 2 2 25 Plymouth Beach Sandy Neck 1 37 Minnesota Lake of the Woods ClandeboyeBay, Lake Manitoba ! 314 Lake of the Woods Long Point, Lake Winnipeg ! 546 Lake of the Woods West Shoal Lake ! ! 273

New York Moriches Shinnecock ! 18 Shinnecock Moriches 1 25 Shinnecock Mecox 1 14 Long Point, Lake Erie WaugoshancePt., Lake Michigan ! 595 Sources:this study (Manitoba, Minnesota),Wilcox 1959 (New York), MacIvor et aL 1987 (Massachusetts),Pike 1985 (Michigan). Valuesrepresent the numberof males,females, and unknown-sexbirds that movedfrom one breedingsite to anotherin successiveyears. 634 HA•C AND ORING [Auk, VoL 105

T^SLE3. Dispersalof Piping Ploversfrom natal sitesto breeding sites.'

Sex b Km Hatch site Breeding site M F U dispersed Manitoba Grand Marais, Lake Winnipeg West Shoal Lake 1 1 -- 70 Stony Beach,Lake Manitoba West Shoal Lake -- 1 1 35 Twin Lakes Beach, Lake Manitoba West Shoal Lake 1 -- 1 25 West Shoal Lake West Shoal Lake 2 2 1 5 West ShoalLake Long Point, Lake Erie 1 -- -- 1,500 Massachusetts Harding Beach Monomoy -- -- 1 22 Michigan WaugoshancePt., Lake Michigan CatheadBay, Lake Michigan -- -- 1 74 WaugoshancePt., Lake Michigan Grand Marais, Lake Superior -- -- 6 112 Minnesota Lake of the Woods West Shoal Lake -- 2 -- 273 Lake of the Wood Grand Marais, Lake Winnipeg 1 2 1 222 New York Atlantic Beach Shinnecock -- 1 -- 101 Mecox Shinnecock 2 2 -- 9 Moriches Shinnecock 2 3 -- 25 Oak Beach Shinnecock -- 1 -- 62 TobayBeach Moriches 1 -- -- 66 Penn Yah Long Point, Lake Erie -- -- 1 240 Sources:This study(Manitoba, Minnesota), MacIvor et al. 1985(Massachusetts), Pike 1985(Michigan), Wilcox 1959 (New York). Valuesrepresent numbers of males,females and unknown-sexfirst-year adults that dispersedfrom their natal site to a non-natalsite to breed.

factors such as intense competition for re- malePiping Plover chicks returned to Manitoba sources (Greenwood 1980, Pusey 1987). Al- and New York in equal numbers.Comparative though extreme casesof inbreeding or out- charadriid data are limited to Mountain Plovers breeding may have detrimental effects on (Charadriusmontanus) where 1 female was philo- individuals and populations(Rails and Ballou patric, and 1 male returned to breed within 10 1983), in many casesdispersal patterns can be km of its hatch site (Graul 1973). Similarly, mo- explained in terms of somaticrather than ge- nogamousscolopacids did not exhibita sexbias netic factors (Shields 1982, Moore and Ali 1984, in natalphilopatty (Oring and Lank 1984).With Dobson and Jones 1986). the low incidenceof natal philopatty in shore- Among monogamousavian specieswith re- birds (Tables 1 and 4; Oring and Lank 1982, source-defensemating systems, males generally 1984), further discussion of sex biases is not exhibit greater natal philopatry and breeding- warranted. site fidelity, whereas females show a greater The significanceof low return rates found tendency to disperse (Greenwood 1980). Be- amongmany avian species (Baker 1978, Shields causemales must acquirea territory in order to 1982) is difficult to interpret without mortality attain a mate, Greenwood (1980) predicted that data,and without knowledge of the socialand higher return ratesamong males to natal sites environmental factors that influence behavior and successivebreeding sites facilitated terri- during all phasesof the annual cycle. For ex- tory acquisitionthrough familiarity with the ample, competitionamong SpottedSandpiper area and its residents. Females have more free- (Actitismacularia) chicks during their natal year dom to choose the best or most resources, and mayplay a primary role in determiningthe rate may find better opportunitiesat non-natalsites. of dispersalor philopatry the following year An alternativehypothesis predicts male-biased (Oring in press).Global competitionfor space philopatrybecause parents prohibit female off- alsomay result in dispersaleven if dispersing spring from returning to natal sitesto parasitize individuals have little chance of success in a their nests(Liberg and von Schantz1985). new, lesscrowded location (Hamilton and May Contrary to either hypothesis,male and fe- 1977). October! 988] PipingPlover Dispersal Patterns 635

GULFOF MEXICO

Fig. 3. Dispersalof Piping Ploversfrom breedingsites to wintering sites,based on 91 sightingsof marked birds.

Breedingdispersal.--Breeding dispersal pat- ever, variability in return patternsamong char- terns among-monogamous charadriid and adriid and scolopacidspecies are equivalent to scolopacidspecies are similar to Piping Plovei:s the variability exhibitedamong local populations in that the majority of adults are site-faithful, of Piping Plovers.These results reflect differ- and return ratesbetween the sexesare not sig- encesamong local populations of Piping Plo- nificantly different (Tables1 and 4; Oring and vers and the nature of particular studies. They Lank 1982, 1984;Haig and Oring 1988b).How- also illustrate that classifyingspecies' trends

T^m,E4. Breeding-sitefidelity and natal philopatry in the .

% return Adults n Chicks return Years/ Speciesa banded return M F Total banded (%) study Source Golden Plover (Pluvialis ! 12 87 78 77 77.7 .41 26 (63.4) 6 Parr 1980 apricaria) Mountain Plover b (Cha- 8 5 62.5 229 2 (0.9) Graul 1973 radrius montanus) Snowy/Kentish Plover 410 243 59.3 1,220 68 (5.5) 9 Rittinghaus 1956 (C. alexandrinus)c 129 91 77 66 70.5 5 Warriner et al. 1986 Common Ringed Plover .... (4.4) 4 Laven 1940 (C. hiaticula) 40 36 100 79 90.0 42 24 (57.1) 4 Pienkowski 1984 (C. vociferus) 31 13 63 20 41.9 48 0 (0.0) 4 Lenington & Mace 1975 White-fronted Plover a 18 18 100 100 100 4 Summers & (C. marginatus) Hockey 1980 Spur-winged Plovera 119 119 100 100 100 70 14 (20.0) 5 Barlow 1972 (Lobivanelluslobatus) ------14 12 (85.7) 3 Thomas 1969 Speciesare monogamousand migratory unlessotherwise specified. Specieshas rapid multi-clutchbreeding system and is migratory. Populationis partially non-migratoryand partially sequentiallypolyandrous. Speciesis monogamousand non-migratory. 636 •aG •a•v O•a•G [Auk,Vol. 105 based on limited numbers of populations or populationdensities that arequite different from geographicareas within species'ranges is un- those at previous sites. Beach habitat appears satisfactory. similar on the , Lake of the Woods, Habitat distribution and availability provide and southern Manitoba; but saline potholes in at least a partial explanation for variability in North Dakota, expansivealkali sloughsin Sas- dispersalpatterns among Piping Plover popu- katchewan, and river sandbars in South Dakota lations. During the first half of this century, and Nebraska could present prohibitive social Piping Ploversand their breeding siteswere or environmental obstacles to newcomers. abundant and were distributed almost contin- Therefore, birds that have bred in an area where uously along the east coastof North America they, or their neighbors,have had a degree of (Bent 1929, Haig 1986). Beachhabitat along the reproductivesuccess may find it advantageous Atlantic coast was fairly homogeneous,com- to return rather than chance failure at an un- pared with inland Piping Plover areas. Low known site.Conversely, when sitesprove to be breeding-site fidelity in New York may have nonproductive, Piping Plovers may improve occurreddue to equivalent options in many lo- their reproductivesuccess by moving to a new cations,and lessenedthe importance of site fi- location. delity. Winterdispersal.--Pair bonds are presumably Conversely, Piping Plovers at Lake of the formed on breeding grounds; and natal and Woods have few available nest sites and no breedingdispersal are responsiblefor the inter- nearby alternate breeding options. The total population genetic mixing that appearsto oc- numberof Piping Plovers(less than 200 birds) cur. Little geneticdifferentiation has occurred and viable breeding sites in the Great Lakes, between local or regional Piping Plover pop- Lake of the Woods, and interlake region of ulations(Haig and Oring 1988b).Furthermore, Manitoba is low (Haig et al. 1988). This leaves allele frequencies in local populations con- few possibilitiesfor birds to move to other pop- formed to Hardy-Weinberg predictions for ulations within the region. Piping Ploversthat equilibrium. Hence, regular gene flow occurs, are not site-faithful at Lake of the Woods must but the mechanism remains unclear. Few Pip- dispersegreat distances to adjacentpopulations. ing Plovers are seen during spring migration Thus, over 90% (n = 26) of birds breeding at and it appearsthat, oncebirds leave winter areas, Lake of the Woods in 1987 were site-faithful mostdo not stop until they are near breeding adults or philopatric chicks (Haig and Oring sites (Haig 1986, Haig et al. 1988). If Piping 1987). Ploversform pair bondsbefore or during spring Piping Ploversin Manitoba representan in- migration,the extentof populationmixing doc- termediate situation. Contrary to Lake of the umentedon winter sitesmay significantly affect Woods, there are a number of local sites to which the geneticstructure of breeding populations. they may disperse.Unlike New York Piping Plovers, birds that leave the interlake region ACKNOWLEDGMENTS must dispersegreat distancesbefore reaching Successof this study was contingent on the coop- another breeding area. Therefore, site fidelity eration of researchers, museums, bird watchers, and is similar to that at Lake of the Woods,but many others who reported distribution and sighting data. birds that are not site-faithful return to the re- We are grateful to T. Amos,T. Eubanks,C. Johnson, gion. Other factorscontributing to dispersalin J. Nicholls, U.S. Fish and Wildlife Service Bird Band- Manitobabirds are discussedin Haig and Oring ing Lab, and the hundredsof othersthat took the (1988b). time to send us information. We thank P. Goossen, Dispersal can be hazardous for any bird, but L. MacIvor, P. Mayer, E. Pike, E. Prindiville, and M. Piping Plovers face a great risk that a new Ryan for sharingunpublished data. Cooperation with the Pan AmericanShorebird Program expanded our breedingsite will be less satisfactorythan a contacts and data base. We thank T. Wiens and F. former site. Throughout their range, nesting Cuthbert for their collaboration in the Lake of the and winter sites are ephemeral and subject to Woods study. Field assistanceduring the breeding frequent destructionor reconfiguration(Haig seasonwas provided by WebsterFellows from Delta 1985;Haig and Oring 1985, 1988b;Dyer et al. Waterfowl and Wetlands Research Station. We were 1987).Inland Piping Plovers,dispersing a great assistedin the winter by E. Cartera G., C. Fernandez distancefrom former sites,may facehabitat and L., J. Haig, and M. Schrank.A. H. Brush,R. Crawford, October1988] PipingPlover Dispersal Patterns 637

L. Hunter, C. Schick,and two anonymousreviewers ß & . 1988a. Genetic differentiation of madehelpful commentson the manuscript.The proj- Piping Ploversacross North America. Auk 105: ect was funded by Delta Waterfowl and Wetlands 260-267. Research Station, World Wildlife Fund (Canada), --, & --.. 1988b. Mateßsiteß and territory World Wildlife Fund (USA), Universityof North Da- fidelity in Piping Plovers.Auk 105:268-277. kota, Manitoba Department of Natural Resources, HAMILTON,W. D., & R. M. MAY. 1977. Dispersalin MinnesotaDepartment of Natural Resources,and Na- stable . J. Theor. Biol. 7: 1-52. tional Science Foundation Grant DCB 8608162 to L. HARRIS, W., G. WAPPLE, R. WAPPLE, K. DESMET, & S. Oring and A. Fivizzani. The National Zoo provided LAMONT. 1984. SaskatchewanPiping Plovers resourcesto S. Haig during manuscriptpreparation. 1984.Reginaß Saskatchewan, Sask. Nat. Hist. Soc. and Sask. Pks. Renewable Resour. HORN, H. S. 1983. Some theories about dispersal.

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