Reproductive Success and Colony-Site Tenacity in Caspian Terns

REPRODUCTIVE SUCCESS AND COLONY-SITE TENACITY IN CASPIAN TERNS

FRANCESCAJ. CUTHBERT• BellMuseum of Natural History,University of Minnesota, 10 ChurchStreet SE, Minneapolis, Minnesota 55455 USA

AI•STRACT.--Co1ony-siteuse by individually marked CaspianTerns (Sternacaspia) was studied at four breeding coloniesin northeasternLake Michigan during 1976-1979.I examined two related aspectsof colony-siteuse: (1) colony-sitepreference in experiencedbreeders and (2) the relationship between reproductive successand colony-sitetenacity. Terns showed a significantpreference for the colonyof previousbreeding unless their precedingreproductive effort was unsuccessful.Caspian Terns tended to use the same colony site if young were producedbut moved to a new locationif reproductivesuccess had been terminated or threat- ened at the traditional site. Received11 Feburary1987, accepted 15 January1988.

SELECTIONof breeding habitat is a crucial de- ger) usually abandonunsuccessful colony sites terminant of avian reproductivesuccess. Many but continue to nest at successful sites. Al- speciesof gullsand ternsare ideal for the study thoughseveral studies have demonstrateda re- of habitat selectionbecause they often nest in lationshipbetween nest-site tenacity (within the dense colonies and exhibit site tenacity, or the samecolony) and previoussuccess (Macdonald tendencyto return to the colonysite or nestsite 1977, Brooke 1978, Ollason and Dunnet 1978), of the previous year providing the habitat re- no study of laridsor other colonialwaterbirds mains suitable (Austin 1949, McNicholl 1975, has focused on the specific relationship be- Burgerand Shisler 1980).Breeding birds appear tweencolony-site tenacity and the reproductive to selectnesting habitat where individuals will history of color-markedindividuals. To deter- have a high probability of maximizing their mine if preferencefor colonysite is influenced reproductivesuccess. Natural-selection theory by whether chickswere raised to fledging at predictsthat individualsproducing offspring at that location in the previous season,I studied a colony site should continue to breed at that colony-sitepreference in experiencedbreeders location as long as it remains relatively un- and the relationshipbetween reproductive suc- changed, whereas birds that have site-related cessand colony-sitetenacity. reproductivefailures (e.g. storm washouts,egg and chick predation,human disturbance)should STUDY AREA AND METHODS move to another breeding colony,use another The study area included four islandsin northeast- nestsite in the samecolony, or starta new col- ern Lake Michigan. Colony siteswere locatedon the ony at another locationfor subsequentnesting northeasternpoint of High Island (45ø45'N,85ø40'W); attempts.I examined the relationship between Hat Island (45ø47'N, 85ø18'W); Shoe Island, a gravel reproductivesuccess and colony-sitetenacity in bar 1 km south of Hat Island; and Ile aux Galets CaspianTerns (Sternacaspia) breeding in north- (45ø41'N, 85ø11'W). The distance between colonies eastern Lake Michigan. ranged from 1 to 39 kin. The study area is described Demonstrationsof the adaptive value of hab- in greaterdetail by Cuthbert (1985b).Approximately itat selection in colonial waterbirds are for the 1,100pairs of CaspianTerns nested at thesesites from most part correlative, but reproductivesuccess 1976 to 1979. These birds represented about 30% of the Great Lakes population during this period; the in Laughing Gulls (Larusatricilla) is related di- rest nested on Gravelly Island (45ø31'N,86ø43'W) in rectly to nest location (Montevecchi 1978, Bur- northwesternLake Michigan or in the Canadian col- ger and Shisler 1980). More recently, Burger onies located on islands in northern Lake Huron (1982) found that BlackSkimmers (Rynchops ni- (North Channel and GeorgianBay) and Lake Ontario (Blokpoel and Fetterolf •978, Shugart et al. 1978, Cuthbert 1985b). • Present address: Department of Fisheries and The Great Lakes exhibit changes in water level Wildlife, 200 Hodson Hall, University of Minnesota, (Cohn and Robinson1976, Larsen 1985), and breeding St. Paul, Minnesota 55108 USA. larids are affecteddirectly by these changing lake

339 The Auk 105: 339-344. April 1988 340 FRANCESCAJ. CUTHBERT [Auk, Vol. 105 levels (Ludwig 1962, 1974; Morris and Hunter 1976; marked CaspianTerns were numbered individually, Southern1977; Shugart et al. 1978;Shugart and Scharf and periodicinspections (every 3-4 days)of nest con- 1983;Cuthbert 1985a,b). Relatively high water levels tentswere made from early incubationthrough band- (abovethe 1900-1979spring average)prevailed in all ing of chicks. In 1978, 28 nests were monitored on yearsof this studyexcept 1977 (U.S. Army CorpsEn- High Island and 48 on Ile aux Galets.In 1979 the nests gineers1976-1979, Shugart and Scharf1983). Caspian were distributed as follows: Hat Island (4), Shoe Is- Terns nested on High and Hat islands and Ile aux land (7), High Island (18), and Ile aux Galets (25). Galetsduring all 4 yr of this studyand on ShoeIsland After the chicks were banded (152 in 1978, 118 in during 1977-1979. When lake levels were above av- 1979),I observedcolor-marked parents and their off- erage, Shoe Island was submergedor so reduced in spring from blinds on the edge of the colonies.Terns size that it was unsuitable as a breeding site, and were consideredto have had a successfulreproduc- portionsof the other siteswere flooded repeatedly tive seasonif one or more chickssurvived to fledging by storm-driven waves during the breeding season. (40+ days). I recordedcause of reproductive failure Data were collected during the breeding season (e.g. storm washout, investigator disturbance,gull (mid-April to mid-August)from 1976to 1979.I visited predation,unknown factors)for birds that produced the colonies on a rotational scheduleby float plane no offspringin a season.Data on reproductivesuccess or boat every 3-7 daysthroughout each season.Field and colony-sitetenacity were analyzed using a Chi- assistantssupplemented my observationswhen I was squaretest (Zar 1974). not present. Capturingand marking techniques.--From 1976 to 1978 RESULTS I captured449 adult CaspianTerns. About 25% (119) were banded at the time of capture,and information COLONY-SITE PREFERENCE IN from the bandswas usedto determine previousnest- EXPERIENCED BREEDERS ing history. Initially, I captured 254 terns (125 on Hat Island and 129 on Ile aux Galets)using a cannon net By analyzing colony-site use records for (Southern 1972) and tagged them with individually breeding adults banded before my study and numbered,vinyl-coated nylon patagialwing markers recaptured during the study period, I estab- (Southern 1971) that were color-codedto colony site. lished two records of site use for 62 terns and Becauseof significant tag loss, I obtained an addi- three recordsfor 13 individuals.Thirty-six (58%) tional 76 birds (28 on High Island and 48 on Ile aux of the 62 birds with two colony-site records Galets) in 1978 using a monofilament line nest snare were nesting at the colony of first capture,and (Zwickel and Bendell 1967)modified to capturebirds around the feet. I marked these terns with unique 26 (42%)were recapturedat a different colony combinations of colored plastic leg bands; there was (Table 1). Of the 13 individuals with three no evidence of leg-band losswithin or between sea- known breeding records,9 (69%) had nested at sons. The bands were more reliable than the wing the same site at least three times, 2 (15%) used markers,and only datacollected on ternscolor-marked the same site at least twice, and 2 (15%) nested with plastic leg bands were analyzed. Observations at three different colony sites. Most (93%) of on colony-siteuse by individuals that retained wing thesebirds were banded initially at coloniesin markers provided supplementary information. To the studyarea. Five (7%)were bandedas adults monitor adult reproductive successI banded chicks at the Charity (44ø01'N,83ø20'W) and Papoose with a U.S. Fish and Wildlife Service aluminum leg (45ø51'N, 81ø20'W) island colonies in Lake Hu- band and plastic band color-codedto colony site. During color-marking operations! recaptured 75 ron, approximately175 and 150 km from the terns that had been captured and banded as breeding recapture site. adults at least one time before my study. I obtained CaspianTerns from the northern Lake Mich- information on the locationof previouscaptures from igan colonies often breed on the same island the U.S. Fish and Wildlife Service Bird Banding Lab- for more than one breeding season;over a num- oratory. ber of yearsindividuals may nestat two or more Intercolonymovements.--From 1977 through 1979 I different colony sites.Recapture data collected spent 1-6 h/day (1,200+ h) locatingmarked individ- periodically over a long period of time, how- uals at Ile aux Galets and High Island; observation ever, cannotprovide an accuratepicture of col- time was divided equally between the sites. I spent ony-siteuse by individualbirds because the data 120 h recording marked terns at Hat Island in 1977 and 1978;these observations were supplementedwith do not supply information on colony-site data collectedby G. Shugartfrom 1977 through 1979. changes within a season or in consecutive I made only 20 h of observationsat the Shoe Island breeding years. To avoid problemsassociated site from 1977 through 1979. with analyzing recapture data, I attempted to Evaluationof reproductivesuccess. --All nestsof color- follow colony-site use by individual terns April 1988] CaspianTern Colony-site Tenacity 341

T^I•I•E1. Colony-site use by banded CaspianTer..•s T^I•LE2. Colony-siteuse by nesting color-banded captured as breedersin 2 years. CaspianTerns in two consecutivebreeding seasons.

Colony of recaptureas 1979 colony Colonyoffirst nestingadult, 1976-1978 capture as Ile aux Hat Shoe High nesting adult Original Different 1978 colony Galets IslandIsland Island Total (before 1976) sited site Total lie aux Galets 22 2 4 4 34 Ile aux Galets 27 16 43 High Island 1 2 3 14 20 Hat Island 0 0 0 Total 25 4 7 18 54 Shoe Island NS 1 1 High Island 9 4 13 Charity Island NS 4 4 PapooseIsland NS 1 1 died between the 1978 and 1979 seasons. Under Total 36 26 62 the extreme assumption that the missing terns

•NS = not sampled. (14 from Ile aux Galetsand 7 from High Island) nested at 1 of 9 other alternative colony sites (Cuthbert 1981),the colony of previousbreed- throughout two consecutivebreeding seasons. ing would still be the colonyof preference(Ile In 1978 I recorded colony-siteuse by 76 terns aux Galets:X 2 = 36.17, df = 4, P < 0.001; High wearing unique combinationsof colored leg Island: X2 = 20.96, df = 4, P < 0.001). I believe bands; I located 55 of these individuals in 1979. that experiencedterns do not selectbreeding Of the 55, 36 (69%) nestedat the site of previous sitesrandomly within the general breeding re- breeding,and 16birds (29%)bred at one of three gion. Although some individuals change sites additional colony sites in northeastern Lake in consecutive seasons,Caspian Terns tend to Michigan (Table 2). One individual was a non- breed at the colony where they nested the pre- breederin 1979and was observedvisiting three vious year. different coloniesfor varying periodsof time. I analyzed colony-site use for 54 terns that REPRODUCTIVE SUCCESS AND bred at known sitesin 1979 to test the hypoth- COLONY-SITE TENACITY esisthat individuals do not show a preference for the colonywhere they initially nestedthe In 1978, 60 (79%) of the 76 birds raised at least previousyear. Individuals originally banded on 1 chick to fledging. In 1979,37 (69%)of the 54 lie aux Galets (X2 = 37.9, n = 34, df = 3, P < individuals recordedbreeding in northeastern 0.001) and birds from the High Island colony Lake Michigan raised at least 1 chick to fledg- (X2 = 22.0, n = 20, df = 3, P < 0.001) showed a ing. A total of 33 nesting efforts failed in both significant preference for the colony of pre- years, and 15 (46%) attempted renesting (i.e. vious breeding. In 1979, 21 marked terns pres- nest reconstructed,1 or more eggslaid) within ent in 1978 were not recorded during obser- 2-3 weeksafter the original nest contentswere vations at the three largest islands. Several destroyed.Storms driven by winds exceeding factors may account for their absence.A bird 80 km/h causedmost (55%) of the failures. My would not have been observed if it lost its color color-markingactivities caused 7 (22%) birds to bands, died after leaving the colony in 1978, deserttheir eggs.On'ly 2 birds abandonedtheir nested on Shoe Island where thorough obser- nestsin responseto handling; the other 5 des- vations were impossible, nested or was a non- erted after Ring-billed Gulls (Larusdelawarensis) breeder at another colony in the Great Lakes punctured their eggswhile I was banding chicks outsidethe study area, or did not return to the in adjacentnests. Another 20%of the nestsfailed Great Lakes for the 1979 breeding season.All for unknown reasons;predation by adjacent terns were banded with 2-4 color bands, and nesting Herring Gulls (L. argentatus)accounted there was no indication of band lossin any of for only 3% of the failures. the 55 color-marked adults that I located in 1979. Using two categoriesof nesting efforts,I de- The other four explanationsmay account for termined if colony-sitetenacity was influenced missingterns. Ludwig (1965) estimatedan 11% by previous reproductive successwithin a sea- annualadult mortalityin the CaspianTern pop- son (intraseasonal) or between seasons (inter- ulation breeding in the Great Lakes. This sug- seasonal). geststhat 8 or 9 of the missing terns may have Intraseasonaltenacity.--Twenty (30%) color- 342 FRANCESCAJ. CUTHBERT [Auk,Vol. 105

TABLE3. Reproductive successof 75 color-banded I made the extreme assumptionthat all missing CaspianTerns in 1978and colony-siteuse in 1979. birds nested at another colony. A test of het- erogeneityof both samplesindicated that the Breedingcolony in 1979 Terns Terns sampleswere homogeneous(X 2 = 1.49, df = 1, Nesting ob- not ob- P < 0.10), and I used pooled data to test the success at Differ- served served 1978 colonies Same ent in 1979 in 1979 null hypothesisthat site useis independentof reproductivesuccess. It was rejected(X 2 = 11.83, Ile aux Galets n = 75, df = 1, P < 0.001). As long as the pro- Successful 23 7 30 11 portion of the unobservedbirds assumedto have Unsuccessful I 3 4 3 renested is equal for both successfuland un- High Island successfulterns, other analysesthat adjust for Successful 13 3 16 2 death and nonbreederswill also result in rejec- Unsuccessful I 3 4 5 tion of the null hypothesis. Total 38 16 21

DISCUSSION

COLONY-SITE PREFERENCE IN marked terns experiencedreproductive failures EXPERIENCED BREEDERS during their first nesting attempt in the year and then renested within the same breeding Recapturesof banded birds and observations season. Sixteen (21%) of the 76 color-banded of color-marked individuals indicate that ex- terns lost the contents of their nests in 1978. Of perienced Caspian Terns in northeastern Lake the 54 color-banded birds located in 1979, 17 Michigan tend to nest at the colonywhere they (32%) failed in their initial breeding attempt. bred the previous year. Staav (1979) found that None of these individuals had failures in both CaspianTerns from the Baltic population also seasons.These 33 birds respondedto the nest show strong tenacity to the colony of previous failuresin a numberof ways:6% renested at the breeding. McNicholl (1975) proposedthat the original colony, 6% remained at the original selectiveadvantage of site tenacity may be the colony but did not renest, 36% deserted the reductionof susceptibilityto predationand oth- original colony and were not observedfor the er negativefactors by familiarizing the bird with rest of the season, 39% renested at a different its surroundings.Several additional benefitsare colony,9% were observedmaking a nest scrape possible.For example, birds that return to the at a different colony but renesting was not es- same colony each year may spend less time tablished,and 3% moved to a different colony searchingfor a colony and nest site and there- but did not renest. Most frequently, birds that fore may breed earlier than individuals that failed responded by deserting their breeding changecolony sites. This advantage•ould be colony. Of those that were known to renest strengthenedif mate retention was enhanced within the same season, 87% relocated at a dif- by birds returning to a colony site. Terns that ferent colonysite and 12%remained at the orig- use a colony in consecutive seasonsalso may inal colony. becomefamiliar with productive fishing areas Interseasonaltenacity.--In 1979 I located 46 in the vicinity. McNicholl (1975) suggestedthat color-banded individuals that had raised at least strong site tenacity would be disadvantageous 1 chick to fledging the previousyear (Table 3). if it promoted the continued use of poor sites More than 75% of these successful birds (36) or sites that changedrapidly or deteriorated, nestedat the colonythey usedin 1978;10 bred and he hypothesizedthat the degree of site te- on a different island.Eight of the 16 birds that nacity exhibitedby individualsin a population failed in 1978 bred in 1979. Two nested at the may reflect the stability of the nesting habitat. same colony,and 6 bred elsewhere.! rejected The relationshipbetween habitat stability and the hypothesisthat colony-site use was inde- site tenacity has been observedin larids that pendent of reproductivesuccess for Ile aux Ga- breed at severalsites of variable stability in the lets (X2 = 4.38, n = 34, df = 1, P < 0.05) and Great Lakes. Ring-billed Gulls that nest on in- High Island (X2 = 4.82, n = 20, df = 1, P < 0.05). undation-prone islandsin northern Lakes Hu- Site-use and reproductive-successdata were ron and Michigan tend to change colony sites reanalyzedincorporating data on missingterns. frequently (Ludwig 1974). In contrast,Ring- April 1988] CaspianTern Colony-site Tenacity 343 billed Gulls from this samepopulation that nest locations despite reproductive failures dem- on a well-protected breakwall in northern Lake onstratesthat selection of breeding habitat is Huron exhibit a high degree of colony-sitete- influenced by multiple factors. In addition to nacity (Southern 1977). reproductive success,these may include previous experiencesat the colony site (e.g. pred- REPRODUCTIVE SUCCESS AND ator or human disturbance,relationship with COLONY-SITE TENACITY mate), local environmental conditions, and availability of alternative breeding sites. Ad- CaspianTerns that raised at least 1 chick to ditional studieson the behavior of individually fledging significantly preferred the same col- marked birds that use adjacentcolony sitesare ony during the subsequentyear, whereasterns needed to enhance our understanding of this that experiencedreproductive failures tended complex issue. to nest at a new colony site on their next attempt. Sample sizes of unsuccessfulbirds were ACKNOWLEDGMENTS too small to detecta difference among responses of birds to different causesof reproductivefail- I thank H. B. Tordoff, E. C. Birney, M. W. Weller, ure, but terns that experiencea disturbancethat and J. L. D. Smith for commenting on earlier drafts potentiallythreatens adult survivalmay be more of this manuscript.The manuscriptwas improved by likely to desert their nestsquickly and perma- commentsfrom H. Blokpoel and an anonymousre- nently. Immediate desertionof colony sitesby viewer. I am grateful to W. E. Southernfor discussion Caspian Terns has been observed or suspected on colony-sitetenacity in Ring-billed Gulls and to J. P. Ludwig, who generouslyshared his banding data following investigator disturbance (Bergman on Caspian Terns. I thank G. W. Shugart, who con- 1953, Shugart et al. 1978), military operations tributed to this study in many ways. I am especially (V•iis•inen 1973), duck hunting adjacent to the grateful to my field assistants,E. Donnelly and A. colony (Bergman 1980), and egg-collectingac- Kraupa, for friendship and enthusiasmthroughout tivities (V•iis•inen 1973, Bergman 1980). Deser- eachfield seasonand to D. DeRuiter, floatplanepilot. tion has been reported in other speciesof terns; I thank the many people in the Michigan Depart- reasonsinclude food shortage in a colony of ment of Natural Resourceswho provided assistance Sandwich Terns (S. sandvicensis;Marpies and in numerousways. The University of Michigan and Marpies 1934), predation on Common Terns (S. Central Michigan University biological stations pro- hirundo)by rats (Rattusnorvegicus), and deser- vided equipment, lodging, and transportation.Nor- ma Essexprepared the final manuscript. tion by Sooty Terns (S. fuscata)as a result of This research was funded by: BergstromAward heavy infestation of virus-infected ticks (Orni- (Northeastern Bird Banding Association), Frank M. thodoroscapensis) (Feare 1976). All of these ex- Chapman Fund (American Museum of Natural His- amples involved factors that potentially have tory), Dayton Natural History Fund (Bell Museum of direct influence on the survival of the adult Natural History), Departmentof Ecologyand Behav- birds. ioral Biology(University of Minnesota),National Au- Although CaspianTerns respondedto repro- dubon Society,Society of SigmaXi, and Wilkie Fund ductive failuresby moving to new colony sites, for Behavior and Evolution (Bell Museum of Natural exceptions occurred. Two individuals whose History). nestswere destroyedby high wavesin 1978did LITEP•TURE CITED not change colonies,and both nested on the same beach ridge as the previous year. Failure AVStIIq,O. L. 1940. Some aspectsof individual dis- to change nest or colony sites despite repeated tribution in the Cape Cod tern colonies.Bird- failure and potential hazardshas been observed Banding 11: 155-169. in other populations of larids and has often 1949. Site tenacity, a behavior trait of the puzzled investigators.For example, Common Common Tern. Bird-Banding 20: 1-39. Terns continued to nest at the samecolony site BERGMAN,G. 1953. Verhalten und Biologieder Raub- seeschwalbe(Hydroprogne tschegrava). Acta Zool. where flooding caused frequent nest failures Fennica 77: 1-50. (Austin 1940), and Southern et al. (1985) re- 1980. Single-breeding versus colonial ported that even after 9 yearsof fox predation, breeding in the CaspianTern (Hydroprognecas- small coloniesof gulls persisteddespite total or pia), the Common Tern (Sternahirundo) and the nearly total annual reproductive failure. The Arctic Tern (Sternaparadisaea). Ornis Fennica 57: fact that birds continue to breed at traditional 141-152. 344 FRANCESCAJ. CUTHBERT [Auk,Vol. 105

BLOKPOEL,H., & P.M. FETTEROLF. 1978. Colonization McNICHOLL,M.K. 1975. Laridsitetenacityandgroup by gulls and terns of the EasternHeadland, To- adherence in relation to habitat. Auk 92: 98-104. ronto Outer Harbour. Bird-Banding 49: 59-65. MONTEVECCHI, W. A. 1978. Nest site selection and BROOKE,M. DE L. 1978. Some factorsaffecting the its survival value among Laughing Gulls. Behar. laying date, incubation and breeding successof Ecol. SociobioL 4: 143-161. the Manx Shearwater(Puffinus puffinus). J. Anim. MORRIS, R. D., & R. A. HUNTER. 1976. Factors influ- Ecol. 47: 477-495. encing desertion of colony sites by Common BURGER,J. 1982. The role of reproductivesuccess in Terns. Can. Field-Nat. 90: 137-143. colony-siteselection and abandonmentin Black OLLASON,J. C., & G. M. DUNNET. 1978. Age, expe- Skimmers(Ryncnops niger). Auk 99: 109-115. rience and other factorsaffecting the breeding --, & J. SHISLER.1980. Colony and nest site se- successof the Fulmar, Fulmarusglacialis, in Ork- lection in Laughing Gulls in responseto tidal ney. J. Anim. Ecol. 47: 961-976. flooding. Condor 82: 251-258. SHUGART,G. W., & W. C. SCHARF. 1983. Common COHN, B. P., & J. F. ROBINSON. 1976. A forecast model Terns in the northern Great Lakes: current status for Great Lakes water levels. J. Geol. 84: 455-465. and populationtrends. J. Field Ornithol. 54: 160- CUTHBERT,F.J. 1981. CaspianTern coloniesin the 169. Great Lakes:responses to an unpredictableen- --, --, & F. J.CUTHBERT. 1978. Reproductive vironment.Ph.D. dissertation,Minneapolis, Univ. biology of CaspianTerns in the U.S. Great Lakes. Minnesota. Proc. Colon. Waterbird Group 2: 146-156. 1985a. Mate retention in Caspian Terns. SOUTHERN,W.E. 1971. Evaluation of a plastic wing- Condor 87: 74-78. marker for gull studies.Bird-Banding.42: 88-91. 1985b. Intraseasonal movement between ß 1972. Use of the cannon-net in Ring-billed colonysites by CaspianTerns in the GreatLakes. Gull colonies.Inland Bird-BandingNews 44: 83- Wilson Bull. 97: 502-510. 93. FLARE,C. J. 1976. Desertion and abnormal devel- 1977. Colony selectionand colony site te- opmentin a colonyof SootyTerns (Sternafuscata) nacityin Ring-billed Gulls at a stablecolony. Auk infestedby virus-infectedticks. Ibis 118:112-115. 94: 469-478. LARSEN,C. E. 1985. A stratigraphicstudy of beach ßS. R. PATTON,L. K. SOUTHERN,& L. A. HANNERS. features on the southwestern shore of Lake Mich- 1985. Effectsof nine years of fox predation on igan: new evidence of Holocene lgke level fluc- two speciesof breeding gulls. Auk 102:827-833. tuations. Environ. Geol. Notes 112. Springfield, STAAv,R. 1979. Dispersal of Caspian Terns (Sterna Illinois State Geol. Surv. Div. caspia)in the Baltic. Ornis Fennica56: 13-17. LUDWIG,J.P. 1962. A survey of the gull and tern U.S. ARMYCORPS OF ENGINEERS. 1976-1979. Monthly populationsof LakesHuron, Michigan, and Su- bulletin of lake levels for the Great Lakes. De- perior. Jack-PineWarbler 40: 104-119. troit, U.S. Army Corps Engineers. 1965. Biologyand structureof the Caspian V•ISXNEN, e. A. 1973. Establishment of colonies of Tern (Hydroprognecaspia) population of the Great Caspian Tern (Hydroprognecaspia) by deserting Lakesfrom 1896-1964.Bird-Banding 36: 217-233. flights in the northern Gulf of Bothnia. Ornis 1974. Recentchanges in the Ring-billed Gull Scandinavica 4: 47-53. populationand biologyin the LaurentianGreat ZAR,J. H. 1974. Biostatisticalanalysis. Englewood Lakes. Auk 91: 575-594. Cliffs, New Jersey,Prentice-Hall. MACDONALD,M. A. 1977. Adult mortality and fi- ZWICKEL, F. C., & J. F. BENDELL. 1967. A snare for delity to mateand nest-sitein a groupof marked capturingBlue Grouse. J. Wildl. Manage.31: 202- Fulmars.Bird Study 29: 165-168. 204. MARPLES,G., & A. MARPLES. 1934. Sea terns or sea swallows. London, Country Life Ltd.