Effectiveness of Social Stimuli in Attracting Laysan Albatross to New Potential Nesting Sites

EFFECTIVENESS OF SOCIAL STIMULI IN ATTRACTING LAYSAN ALBATROSS TO NEW POTENTIAL NESTING SITES

RICHARD H. PODOLSKY • Universityof Michigan,School of Natural Resources,Ann Arbor,Michigan 48109 USA

Al•sTRACT.--Seabirdcolonies usually grow as first-time breeders join existing groups. I testedthe hypothesisthat the presenceof conspecifics,specifically the sight and sound of establishedbreeders, was the stimulus responsiblefor first-time breeders to join existing colonies.The attractivepower of conspecificswas testedby presentingto conspecificsmodels of LaysanAlbatross (Diomedea immutabilis) in severalbehavior postures, with accompanying recordings of vocalizations. I found that Laysan Albatross landed more frequently in areas where both albatrossmodels and vocalizationswere present than in areaswith only visual stimuli or no vocal stimuli. Landing albatrossand those on the ground were found nearer to the artificial social stimuli than would be expectedfrom a random distribution. Three- dimensionalmodels were more attractivethan two-dimensionalmodels, and paired models were more attractive than single models for both three-dimensionaland two-dimensional models.Three-dimensional models in a sky-pointingposture were the mostattractive overall, whereas models in head-forward posture were the most attractive two-dimensional models. Albatrossexhibited courtshipbehavior closerto the modelsthan would be expectedfrom a random distribution. The implicationsof attraction to endangeredbird managementand restorationare discussed.Received 3 April 1989,accepted 14 August1989.

COLONIALseabirds probably use the sight and Fretwell and Lucas(1969) suggestedthat the sound of conspecificsto selecta breeding site fitnessof colonial organismsincreases with an (Darling 1938; Lack 1954, 1966; Orians 1966; increasein the number of conspecificsup to a Evansand Cash1985). The presenceof breeding point. Then it declinesbecause of density-de- conspecificsis a strong indicator that a site is pendent factorssuch as increasedcompetition, safeand productive.This hypothesis,first pro- predation, or disease.According to Fretwell and posedby Darling (1938),predicts that prebreed- Lucas, colonial birds should continue to join ing colonial birds are attracted to the stimuli groups of conspecificsuntil the groups reach associatedwith an active group of conspecifics sucha size that density-dependentfactors begin (Klopfer and Hailman 1965). Subsequentstud- to operate. ies of breeding-siteselection by colonial birds I testedthe conspecificattraction hypothesis (Buckley1979, Buckleyand Buckley 1980) and by observingthe behaviorof LaysanAlbatross noncolonialbirds (Cody 1981)have focusedon in the presence of experimentally presented the role of vegetation structure, presenceof socialstimuli. My specificobjective was to learn competitors and predators, and environmental about the mechanisms involved in the forma- productivity. tion of LaysanAlbatross colonies by observing Darling (1938), Lack (1954, 1966), and Orians albatrossbehavior in the presenceand absence (1966) hypothesized that the social stimuli as- of modelsand recordedvocalizations. My sec- sociatedwith an activecolony, such as sight and ond objective was to derive information that sound of conspecifics,attract individuals to a could be used to encouragenesting of Laysan breeding site. They argued that for prebreeders Albatross. the presenceof breeding conspecificsindicates that a locality is both safe and productive rel- METHODS ative to unused localities. This predicts that colonial birds will be more likely to settle in lo- Studyareas.--The experimentswere conductedat calitiesthat already have breeding conspecifics. Kilauea Point, the northernmost point on the main Hawaiian Island of Kauai, from December 1982 to April 1983. Kauai, at the northwest end of the main Hawaiian Island group, is 5 million years old and of I Present address: Island Institute, 60 Ocean Street, volcanic origin (although no active volcanism has oc- Rockland, Maine 04841 USA. curred for 3 million yr) (Carlquist 1970).

119 The Auk 107: 119-125.January 1990 120 R•CHAROH. PODOLSKY [Auk, Vol. 107

were hand-cutfrom three-quarter-inchplywood and painted realisticallywith latex paint. Auditorystimulœ--A recording of LaysanAlbatross vocalizationswas played from 0600--1800 every other day at 12 experimentalplots at KilaueaPoint. The originalalbatross vocalizations were recordedat Mid- way Island and included all the vocalizations de- scribedfor LaysanAlbatross by Sparling (1977). Fieldplacement of the stimuli.--Eighty-onealbatross modelsand twelve speakerswere placedso that each model and speakerhad an equal probability of at- tractingan albatross.The resultingdensity of models per m2 was 50%of the densityof LaysanAlbatross at the breeding colonyon Midway Atoll. This was done Fig. 1. A live albatross(indicated with arrow) vis- to minimize the possibility that albatross would its a pair of two-dimensionalmodels in 1 of 12 study avoid the experimentalareas because they appeared plots. saturated.Fisher (1966) found ca. 1 albatrossper 5 m2 in the colony on Midway Atoll in December 1962. Since the winter of 1975-1976,Laysan Albatross The 81 albatrossmodels in the three study areasre- have visited and attemptedto breed at two locations suitedin a densityof ca. I model per 10 m2. on Kauai: (1) a volcanic crater on the windward The four speakersin each study area were placed (northeast) shore which includes the 13.4-ha USFWS 25 m apart in a linear arrangement down the long AdministrativeFacility at Kilauea Point and an ad- axis of each field. Each of the four speakerswas lo- jacentarea known as Crater Hill, and(2) theU.S. Navy catedin the center of an experimentalplot, and each PacificMissile Range Facility at BarkingSands, a low was camouflagedwith vegetation.Three speakersper sand dune area on the leeward (southwest) shore area were encircledby six different albatrossmodel (Zeillemakerand Ralph 1977,Byrd and Teller 1979, sets,and one speakerwas not encircled by models. Telfer 1980). The establishment of these two rela- The six albatrossmodel setspresent on each experi- tivelyrecent colonies has been hampered by dogpre- mentalplot were (1) a single2-D sky-pointingmodel dation, human disturbance,and periodic outbreaks (2) a single3-D sky-pointingmodel, (3) a pair of 2-D of avian pox (Telfer 1980). sky-pointingmodels, (4) a pair of 3-D sky-pointing Approximately400,000 Laysan Albatross nest in the models,(5) a single 2-D head-forwardmodel, and (6) northwestHawaiian Islands, and a smallcolony exists a pair of 2-D models--one sky-pointing, one head- on the mainisland of Niihau (Berger1981). Nesting forward. The two modelsin a pair were positioned of the LaysanAlbatross in the main Hawaiian Islands to face each other at a distance of 30 cm. was first observed on Moku Manu Islet off Oahu in The albatrossmodels in eachplot were placedevery 1947(Fisher 1948). Laysan Albatross bones have been 4.4 m in a circle around a speaker. Each circle found in subfossildeposits on Kauai and Molokai, of models had a diameter of 10 m, and a radius of 5 which indicatesthat breedingpossibly occurred in m from the centrally placed speaker. The order in the mainislands before the arrivalof the Polynesians which the models appeared on the circle was ran- 1,500yr ago (Olson and James1982a, b). domized for each experimental plot. Each circle of Three study areas(ca. 30 m x 100 m) were estab- modelscontained one empty space in whichno models lished at Kilauea Point. In each area, visual social were set (Fig. 1). stimuli (albatrossmodels) and auditory stimuli (re- Data collection.--Visitationbehavior of LaysanAl- cordedalbatross vocalizations) were presentedto sim- batrosswas compared in three contexts:(1) Kilauea ulate the sight and soundof an establishedLaysan Point, with albatross models and recorded vocaliza- Albatrosscolony. tions, (2) Kilauea Point, with models but no vocal- Visual stimuli.--The albatross models were realistic izations, and (3) Crater Hill, an adjacentcontrol area three-dimensional(3-D) forms and stylized two-di- with no models or recorded vocalizations. All obser- mensional (2-D) forms. Three 3-D models were du- vationswere madewith binocularsand spottingscope plicated from a life-size original, hand-carvedfrom by two observersin the top of the Kilauea Lighthouse basswood.The 3-D modelswere all in the sky-pointing tower. The lighthouse is 20 m tall and is locatedon posturewith wings dose to the body, head pointed a cliff 70 m abovethe PacificOcean. All experimental skyward,and neckfully extended.The sky-pointing plots at Kilauea Point and the reference area at Crater postureis a staticdisplay performedduring Laysan Hill could easily be seen from the top of the tower. Albatrosscourtship (Moir 1946,Meseth 1968).Two- The location and behavior of albatross in the air dimensionalmodels were in two postures:sky-point- and on the ground were monitoredfor Kilauea Point ing and head-forward.The head-forwardposture is a and Crater Hill for a total of 362 h from I December restingposture of a standingalbatross. The 2-D models 1982through 30 April 1983.We collecteddata on the January1990] SocialStimuli Attract Albatross 121

T^nnE1. The observed and (expected) number of 3o albatrossthat landed on study area. • 25 Landed • 20 Study area Total Total per hour (stimuli) fly-by landed ( x 10-2) No visual/no auditory 877 16 (46) 4.3 Visual only 1,300 68 (69) 18.5 Visual and auditory 1,053 86 (55) 23.8 Total 3,240 170 -- 0 1 2 3 4 5 6 7 8 9 10 11 12

Distance (m) Fig.2. The percentageof albatrosslandings at 1-m total number of albatrossflying over the two areas, intervals from the albatross models. The bars are ob- the location of all albatross at the moment of land- servedlandings. The line is expectedlandings if ran- ing, and the locationand behavior(standing, sleep- dom (x2 = 256.66,df = 11,P < 0.001,n = 154landings). ing, sitting, preening, or courting) of all albatross on the ground. A courtingalbatross was defined as an individual involved in a courtshipdance with one or morealbatross or individualsposturing to one or more models(Meseth 1975,Lefebvre 1977). Data on flying variances.Nonparametric statistics were used when and landing albatrosswere collectedcontinuously. theseassumptions were violated.Probability levels Data on albatross on the ground were col- of <0.05 were consideredsignificant. lectedat 15-min intervalsby the scanmethod (Simp- son and Simpson1977). RESULTS The testfor attraction.--Thedistance from each albatross to the nearest stimulus was recorded for all The percentageof albatrossthat landed var- birds on the ground and at the moment of landing ied significantlybetween the experimentaland at Kilauea Point. The observed distribution of alba- reference areas (Table 1). At Crater Hill, where trossat a particulardistance from the artificial stim- visual and auditory stimuli were not presented, uli was comparedwith the expecteddistribution. I only 16 (1.8%)of 877 albatrossobserved flying calculatedthe expecteddistribution by multiplying theproportion of totalarea available at successive1-m actually landed. When only the visual stimuli distancesfrom the stimuli by the total number of were presented at Kilauea Point, 68 (5.2%) of albatross observed. If albatross were distributed 1,300flying albatrosslanded, whereas 86 (8.2%) closerto the stimuli than expected(assuming a ran- of 1,053 flying albatross landed on days dom pattern of visitation),attraction was assumedto when both the visual and auditory stimuli were have occurred.Conversely, if albatrosswere farther presented (X2 = 38.73, df = 5, P < 0.01, Table from the stimuli than expected,I assumeddisinterest 1). Albatrosslanded significantlycloser to vi- (Marlet 1968). The relative attractivenessof the dif- sual stimuli than expectedfrom a random pat- ferent stimuli was measuredby comparingthe num- tern of landing, which indicated that they were ber of bird observations closest to each stimulus with attracted to the stimuli before landing (X2 = a random expectednumber of observations.I esti- matedthe expectednumber of bird observationsfor 256.66, df = 11, P < 0.001; Fig. 2). eachmodel type by calculatingthe proportionof each Of 601observations of albatrosson the ground model type of all 81 modelsmultiplied by the total at Kilauea Point, 55% were observed within 3 number of albatross observations. Because there was m of a stimuli. Overall, albatrosswere signifi- an equal number of each model type, the expected cantly closer to the stimuli than the expected number of albatross observations was the same for all distribution (X2 = 649.79, df = 11, P < 0.001, model types. Fig. 3). Data analysis.--Datawere analyzed on the Univer- Albatross on the ground were attracted to sity of Michigan Amdahl 470V/8 computer using some models more than others. Of the alba- M.I.D.A.S. (Fox and Guire 1976)and a Sharp EL-512 trosson the groundat Kilauea Point, 28%were programmablecalculator. Statistical tests performed closestto the pair of 3-D sky-pointing models were the Chi-squaretest and the Z-test (Zar 1974). Assumptionsof normalityand homoscedasticityof (Fig. 4). This was a significant departure from parametricmodels were examined by analysisof vari- the expected distribution of 12.5%,and it in- ance, residual analysis,scatter plots, skewnessand dicates that albatross exhibited choice among kurtosiscoefficients, and tests for homogeneityof stimuli (X2 = 235.98, df = 7, P < 0.001). 122 RICHARDH. PODOLSKY [Auk,Vol. 107

30 g 60

i 20 •{5ø 40

•i5 5• 2ø 10 o • o 1 2 3 4 5 6 ? 8 9 10 11 12 1 2 9 4 5 6 ? 8 9 10 11 12+ Dist•uce (m) Distance(m) Fig. 3. The percentageof albatrossobservations Fig. 5. The percentageof courtshipbehavior ob- on the ground at 1-m intervals from the albatross served at 1-m intervals from the albatross models. The models. The bars are observed albatross distribution. barsare the observeddistribution of courtshipbe- The line is expectedalbatross distribution (X2 = 649.79, haviors.The line is the expecteddistribution of court- df = 11, P < 0.001, n = 601). ship behaviors (X• = 347.57, df = 11, P < 0.001, n = 97).

Albatrosswere more attractedto 3-D sky- pointing models than to 2-D sky-pointing seabirds,and albatrossin particular,spend sev- models (z = 3.11, P < 0.001). When the attrac- eral years visiting potential breeding sites be- tivenessof all single modelsis comparedwith fore reachingsexual maturity (Fisherand Fisher all pairedmodels, albatross were significantly 1969,Podolsky 1985).I demonstratedthat their closerto the paired models than to the single behaviorduring this prospectingperiod can be models (z = 7.44, P < 0.001). manipulated.It is likely that sustainedartificial Of the 95 observations where albatrosses were stimulationof a prospectedsite for severalyears closestto the speakers,76% occurredon days couldresult in the establishmentof a breeding when the speakerswere on versus24% on days colony.One or two pairs of LaysanAlbatross when the speakerswere off (z = 0.9521, P < have unsuccessfullyattempted to breed at Ki- 0.01). Of the 97 observationsof courtship at lauea Point each year since the attraction ex- Kilauea Point, 66% occurred within 3 m of a periments. visual stimulus.Overall, albatrosscourted sig- Both models and vocalization playbacksof nificantly closerto the modelsthan the expect- seabirds have been used to attract birds to suit- ed pattern (X2 = 347.57,df = 11, P < 0.001,Fig. able nestingsites: Little Terns (Sternaalbifrons; 5). Britton 1982, Kotliar and Burger 1984), Com- mon Terns (S. hirundo)and Arctic Terns (S. par- DISCUSSION adisaea)(Kress 1983), BlackSkimmers (Rynchops niger;Slaydon 1981), White-tailed Tropicbirds Modelsand vocalizations attracted both flying (Phaethonlepturis; Wingate 1978),Atlantic Puf- LaysanAlbatross and thoseon the ground.Many fins (Fraterculaarctica; Kress and Nettleship 1988),Leach's Storm-Petrels (Podolsky and Kress 1989), and Dark-rumped Petrels (Pterodroma 2 3-D Sky-point 28% phaeopygia;Podolsky and Kressin prep.).In sev- 2 2-D Sky•point frtead eral of these studies, however, models, sound, forward • 18% 2-D He•l -forw•d • 16% or both were used in conjunction with either predator control or substratemodification. To- 2 2-D Sky-point gether these studies indicate that nest-sitese- 1 3-D Sky-point lection can be manipulated. 1 2-D Sky-point The receptivity of LaysanAlbatross to the No model • 4% artificialsocial stimuli may be explainedby their o • fo i• •o 2• 3b dependenceupon colonial breeding. Alexander Percent of observation (1974) and Hoogland and Sherman(1976) pro- Fig. 4. The percentage of observationsof alba- posedthat coloniality evolveswhen the advan- trossesclosest to eachalbatross model type 0{2 = 235.98, tages of group breeding outweigh the disad- df = 6, P < 0.001, n = 601). vantages.They argue that there may be only January1990] SocialStimuli Attract Albatross 123 three evolutionary advantagesto coloniality: that include habitat restoration, control of ex- lower susceptibility to predation (Hamilton otic mammals, and reestablishment of popula- 1971), improved foraging, and an increasein tions by way of translocation. the probability of meeting or gaining a mate. Because albatross are colonial breeders, the ACKNOWLEDGMENTS sight and sound of conspecificsat a particular I am grateful to my graduateadvisors at the Uni- site is a strong indication that the site is worth versity of Michigan, Bobbi Low and Ron Drobney, visiting. My results support strongly the im- for their encouragement.I thank Dominick DellaSala, portanceof conspecificsin the breeding-sitese- Kay Sicheneder,Nat Wheelwright, Bill Drury, Brian lection processamong albatrossand perhaps Nelson, and Steve Kressfor their helpful comments other colonial birds. Visual and auditory dis- on earlier draftsof this paper.The U.S. Fishand Wild- plays function in a variety of contexts.These life ServiceRefuge Departmentgave permissionto may include mate attraction(Tinbergen 1953, study Laysan Albatross at Kilauea Point. The staff at the Kilauea Point Administrative Facility, includ- 1959), mutual mate assessment (Nisbet 1973, ing Noreen Baptista,Barry Brady,Dan Moriarity, and 1977; Simpson 1973), maintenence and RobertShallenberger, were mosthelpful. I alsothank strengthening of the pair bond (Smith 1977), JohnWarham who first suggestedthe attractionwork coordinationof intrapair activitiessuch as nest for Laysan Albatross at Kilauea Point. Tom Telfer relief and feeding of the young (Smith 1977), of the Stateof Hawaii Department of Land and Nat- development of speciesrecognition (Norton- ural Resourcesgranted me permission to study al- Griffiths 1967; Beer 1970, 1975), synchroniza- batrosses at Moku Ai Ai Islet and other areas outside tion of colonial breeding (Darling 1938), and of Kilauea Point. For assistance in the field I thank attraction of prebreedersand first-time breeders David Fairman Jickling. This paper benefited from to the colony (Lack 1954, 1966; Orians 1966; reviewsby RogerEvans and an anonymousreviewer. This study was made possibleby grants from the Podolskyand Kress 1989). University of Michigan Horace H. RackhamSchool Both the landing behavior and the distribu- for GraduateStudy and the Center for Field Research. tion of albatrosson the ground at Kilauea Point indicate that albatross were attracted to the ar- LITERATURE CITED tificial stimuli. Albatrossappeared significantly ALEXANDER,R. D. 1974. The evolution of social be- closerto pairs of modelsthan to single models, havior. Annu. Rev. Ecol. Syst. 5: 325-383. to 3-D models than to 2-D models, and to sky- BEER,C. G. 1970. Individual recognitionof voice in pointing modelsthan to head-forward models. socialbehavior of birds. Pp. 27-74 in Advances I suggestthat LaysanAlbatross are sensitivenot in the study of behavior (D. S. Lehrman, R. A. only to the realism of the stimuli but to the Hinde, and E. Shaw, Eds.). New York, Academic socialgrouping and behavioralstate of the stim- Press. uli aswell. The active speakerswere alsoa point- 1975. Multiple functions and gull displays. sourceof attraction. This pattern of "choice" is Pp. 16-54 in Functionand evolution in behavior difficult to interpret becauseof the diversity of (G. Baerends,C. Beer, and A. Manning, Eds.). functionsthat have been attributedto courtship Oxford, Clarendon Press. displays. BERGER,A. J. 1981. Hawaiian birdlife. Honolulu, Univ. Hawaii Press. There are presently 60 speciesof endangered BRITTON,E. 1982. Least Tern managementby pro- colonial birds; of these, 30 are seabirds(King tectionof nestinghabitat. Paper presented at the 1981).Many are endangeredbecause of the de- 1982 Northeast Conf. Wildl. Soc. struction of their coloniesby introduced pred- BUCKLEY,F. G. 1979. Colony site selectionby colo- atory mammals(King 1981).Attraction of pros- nial waterbirdsin coastalNew Jersey.New York, pectingbirds to safesites shows great potential Proc.Colon. Waterbird Group, October1978: 17- for managing threatened seabirds.This is es- 26. pecially true where prebreedersare known to --, & P. A. BUCKLEY. 1980. Habitat selection and prospectat predator-free sites or at sites where marine birds. Pp. 69-112 in Behaviorof marine predators have been eliminated. To the extent animals.Vol. 4, Marine birds (B. Olla and J. Burg- er, Eds.). New York, Plenum Press. that the data reported for LaysanAlbatross are BYRD,G. V., & T. C. TELFER.1979. LaysanAlbatross applicableto other colonialbirds, attraction by is attempting to establishbreeding colonieson way of simulatingsocial stimuli may aid in their Kauai. Elepaio 38: 81-83. management and restoration. Attraction pro- CARLQUIST,S. 1970. Hawaii: a naturalhistory. New gramscould augment other management efforts York, Nat. 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