Arctic Terns Nesting in Montana: First Modern Interior Breeding Records for the Lower 48 United States

Arctic TernsNesting in Montana: First ModernInterior BreedingRecords for theLower'48 United States

StephenJ. Dinsmore 612 1/2 WestMagnolia Street FortCollins, Colorado 80521 ([email protected])

JoelG. Jorgensen 1218 JacksOnStreet Blair,Nebraska 68008

Abstract TheArctic Tern (Sterna paradisaea) is a circumpolarspecies that breeds BreedingBiology throughoutArctic regions of thenorthern hemisphere and winters at sea ArcticTerns typically breed in coastalareas and on islands,although m southernhemisphere oceans. During migration, the species ishighly somenest at a varietyof inlandsites associated with largerlakes and pelagac,although a fewindividuals regularly occur inland on migration. rivers.They nestin a wide rangeof openhabitats including beaches, ArcticTerns are rare vagrants in theGreat Plains, with apparentmigrants dunes,sand spits, low islands,and marshytundra, always near water accountingfor all previousrecords. Here we report the occurrenceof (Godfrey1966). They may nest eithercolonially or in isolatedpairs nestingArctic Terns in 1998, 1999,and 2000 at BowdoinNational (Godfrey1966), sometimes with otherspecies of gulls(Larus spp.) and WildlifeRefuge in north-centralMontana and comment on thestatus of CommonTerns (S. hirundo)or AleutianTerns (S. aleutica)(Hawksley the specieselsewhere in the GreatPlains. 1957).The breedingseason extends from earlyMay throughJuly; nest initiationis earliestat southernlatitudes and progressively later at more Distribution northerlylatitudes (Bent 1963). Mean dutch sizefor Arctic Ternsis 2 ArcticTerns are widespread breeders across tundra regions of theArctic eggs;one- and 3-eggdutches are less frequent (Bent 1963, Baicich and (Cramp1985). They nest on opentundra, mostly above 50 ø N latitude Harrison1997, Robinson et al. 2001).Eggs are laid at intervalsof one- andfarther north than any other tern species(Cramp 1985). The south- two days,and incubationmay beginwith eitherthe first or secondegg ern hmitsof their breedingrange in North Americalie in northern (Bent1963). Incubation is typically20-22 days(Godfrey 1966, Balclch British Columbia, northeastern Alberta, northwestern Saskatchewan, andHarrison 1997). Nest success varies temporally and geographically, northern Manitoba, northern Ontario, easternQuebec, and Nova Scotia with an averagenest successof about 70% (seeCramp 1986).After (Godfrey1966, American Ornithologists' Union 1998). A few breed hatching,the semi-precocialyoung remain near the nest,where both alongthe Atlantic Coast south to Massachusetts(Veit and Petersen 1993) parentstend them; they fledge at 19-24days (Cramp 1985, Baicich and and along the Pacific Coast south to Washington (American Harrison1997). Young birds remain dependent upon the adultsfor up to Ornithologists'Union 1998). There are four breedingrecords for two monthsafter fiedging (Cramp 1985). Most Arctic Terns do not breed Wisconsinbetween 1871 and 1891 (Kumlien and Hollister 1903, Robbins until agefour, though some begin breeding as earlyas two yearsand 1991), but none of these is mentioned in a more recent reference someas late as five (Cramp 1985). (AmericanOrnithologists' Union 1998).We are awareof no otherinte- rior breedingrecords of ArcticTern for the Lower 48 UnitedStates. There Evidenceof Breedingin Montana is alsoone report of an ArcticTern hybridizing with a Forster'sTern (S. On 14 June1998 we wereconducting a shorebirdsurvey at Bowdom forsten)along the centralCalifornia coast (Roberson et al. 1999).Arctic NationalWildlife Refuge in PhillipsCounty, Montana. This 6300-hectare Ternsundertake one of the longestmigrations of any bird species-- refugeis located11 km eastof Maltaand contains a varietyof habitats approaching35,000 km annually--asthey travel between their Arctic includinga largefreshwater lake with extensivemarshes and surround- breedinggrounds and their wintering grounds, as far southas 74 ø S lati- ing grasslands.At 1108MDT we sawan adultArctic Tern (Fig. 1) at the tude in southernoceans (Bent 1963). Most are thoughtto winter in southeastend of LakeBowdoin. At approximately1215, we noted a sec- Antarcticpack ice between 55 ø E and 155ø E longitude(Cramp 1985). ondadult, and we studiedand photographed both birds until 1235.Both

NORTH AMERICAN BIRDS 55 127-131 127 birds were alternately foraging along the lakeshoreand restingon a nearbysandbar with several Common Terns. The combination of a shorter,blood-red bill, contrastingwhite cheek, dark graybelly, short-winged appearance, pale grayupperwing, pattern of narrowblack edges to the undersidesof the primaries,and higher- pitchedcall notes separated these birds from the Common Terns. When perched, the birds showed a distinctive short-legged,hunch- backedappearance. We suspectedthat theArctic Ternsprobably arrived on southerlywinds just prior to the passageof a cold front on 13 June. Arctic Terns are well known as late spring migrants,and we assumedboth birds would resumetheir northwardmigration when the weather cleared. The mid-lune date seemed normal for a migrantArctic Tern at thislatitude, but we certainlydid not anticipatethat the terns would remain and nest. On 16 June, we returned to the location of our originalsighting and were unable to relocate the terns.Later that day we found two adult Arctic Ternsalong the northeastshore of Lake Bowdoin,just east of LongIsland. Although this locationwas approximatelysix km from our Fig.1. ArcticTern in flight at BowdoinNational Wildlife Refuge, Montana, 14 June1998. Photo by StephenJ. original sighting,we assumedthey were the Dinsmore same terns we had seen on 14 June. The birds spentmost of their time on a small rock and nearbysand spit. We againconfirmed our original identification and took several additional photographs. On 17 June both adults were still at the same locationeast of LongIsland. On thisoccasion we notedthat the birdswere actively courting (Fig. 2). The flightdisplay consisted of a shortchase by the male in typicalstiff-winged flight, the wingsheld upward in a deepvee (Cramp 1986). The male broughtseveral small (<5 cm) min- nowsto the female.Although we cannotbe cer- tain, the minnows appearedto be Fathead Minnows( Pimepahles promelas); Carp ( Cyprinus carpio)and Brook Stickleback(Culaea incon- stans)also occur in LakeBowdoin. The birds also spentconsiderable time on the smallsand spit, althoughwe did not observenest building. Both adults were very territorial, and we watched them chaseaway Blue-winged Teal (Ariasdis- cors),Killdeer ( Charadriusvociferus), American Avocets(Recurvirostra americana), and Ring- billed Gulls (Larus delawarensis).Although it seemedhighly improbable,we suspectedthe birdsmight attempt to nest. On 18 June,nest scrapingand copulation were seenat this location(C. R. Carlson,pets. comm.). On our next visit on 20 Junewe found an adultArctic Tern incubatinga nestcontain- ing one egg.A secondadult was nearby,and a Fig.2. ArcticTerns in courtshipat BowdoinNational Wildlife Refuge, Montana, 17 June1998. Photo by StephenJ. third adult was frequentingthe southeastern Dinsmore. shore of Lake Bowdoin. Both members of the

128 NORTH AMERICAN BIRDS ArcticTerns Nesting in Montana

nestingpair werevery vocal when we werenear the nest. The nest was on a small sandbar less than one-half m above the waterline and con- sistedof a shallowscrape lined with pebblesand bits of vegetation.The nestand eggresembled thoseof a CommonTern (Dinsmore, pets. ohs.) and were consistent with those of an Arctic Tern (Baicich and Harrison 1997). The nest con- tainedtwo eggswhen it waschecked on 28 June and 3 July(Fig. 3). The nestwas still being incu- batedon 6 July.Between 6 and 10 July,the nest wasinundated by risingwater levels. During this period, refuge staff elevatedthe nest in an unsuccessfulattempt to saveit from beingflood- ed. Had the nest been successful,it should have hatchedon approximately10 July,assuming a normalincubation period. After the nestfailed, the terns became much more difficult to locate, and our lastsighting was of a singleadult near the nestsite on 5 August. On 30 May 1999,Dinsmore and DavidC. Ely observeda pair of adultArctic Terns courting at the 1998 nest site. A third adult Arctic Tern was also presentbut did not engagein courtship activity.By 31 May the pair had constructeda nest within two m of the location of the 1998 Fig.3. ArcticTem nest at BowdoinNational Wildlife Refuge, Montana, 3 July1998. Photo by Stephen J. Dinsmore. nest.The nestcontained two eggson 4 June.On 22 Junethe nestwas empty, and there was no signof the adults,indicating that the nesthad failed.On 3 July,Dinsmore and Ely discovereda secondnest containing one eggapproximately threekm from the first nest(Fig. 4). A pair of ArcticTerns defended the nestand, once again, a third adult wasseen nearby. We suspectedthis wasa re-nestingattempt by the originalpair. On 24 July the nest containedone egg and was defendedby both adults.The eggwas still pres- ent on 1 August,but we saw no sign of the adults.We condudedthat the eggwas probably infertile because it should have hatched no later than 25 July,assuming a normal incubation period. We observedboth adults engagedin courtshipactivity on an adjacentisland on 1 and 3 Augustbut not thereafter. On 20 May 2000,Dinsmore and Aaron Brees observeda pair of ArcticTerns courting near the second 1998 nest site. We returned to this site on 24 Juneand discovereda nest containingtwo pipping eggs.At least two other adult Arctic Ternswere nearby.Assuming a normal incubation period,we calculatedthat thisnest was ini- tiated sometime around 1 June. When we next visitedthe nestsite on 1 July,we sawno evidence of the adultsor youngand condudedthat the younghad beendepredated, if theyhad in fact hatched. The terns became much more difficult to locatethereafter, and our lastsighting was of a singleadult near the nestsite on 21 July. Fig.4. ArcticTern nest site at BowdoinNational Wildlife Refuge, Montana, 3 July1999. Photo by StephenJ. Exceptfor the geographiclocation, all of Dinsmore. thesenesting attempts were quite normal. All of

VOLUME 55 (2001), NUMBER 2 129 the nestswere on smallgravel spits along the margin of a largefreshwa- Threespecies of Sterna(Common, Forster's, and Least) occur regu- ter lake,much like the habitatused by ArcticTerns within their normal larlyin theGreat Plains. Within this region, Common Tern breeds only breedingrange. The nestsites were very exposed and werenot in taller in Montanaand the Dakotas.In Montana,it is a locallycommon breed- vegetationlike the nestsof CommonTerns (Dinsmore, pers. obs.). Our ing bird, mainly in the northern half of the state (Montana Bird nestinitiation dates of 1 June,4 June,20 June,and 3 Julyall fall within DistributionCommittee 1996). In 1997approximately 110 pairs nested thenormal range of dateslisted by Bent(1963). To the best of ourknow- on theDry Lakeunit of BowdoinN.W.R., but fewernested there in 1998, ledge,none of thesenesting attempts was successful. It is possiblethat 1999,and 2000 (S. J.Dinsmore, pers. obs.). Forster's Terns breeds more eggsfrom the 2000nest hatche& It is interestingthat these nesting Arctic widelyin in theGreat Plains, from Montana and North Dakotasouth to Ternswere not associatedwith the nestingcolonies of Common or Colorado,New Mexico and Kansas. In Montana,it breedslocally at scat- Forster'sTerns; their nestswere a minimum of two km from the nearest tered locationsthroughout the state (Montana Bird Distribution CommonTern colonyand four km from the nearestForster's Tern Committee1996). Forster's Tern is an uncommonmigrant and rare and colony.Although they had the opportunityto nestamong other species irregularbreeder at BowdoinN.W.R., with a fewpairs nesting there most of Sterna,these Arctic Terns nested elsewhere. years.Least Terns breed locally in everystate in the GreatPlains except Wyomingand New Mexico,mainly alongthe Missouri,Platte, and Status in the Great Plak•s ArkansasRiver drainages and in coastalTexas. In Montana,it breedsvery Fourspecies of smallSterna have occurred in theGreat Plains: Common, locallyalong the Missouriand YellowstoneRivers in extremeeastern Arctic, Forster's,and Least(S. antillarutn)Terns. In this article,we have Montana (Montana Bird Distribution Committee 1996). definedthe Great Plainsregion to includeten states(Montana, North ArcticTerns are rarevagrants in the GreatPlains, although records Dakota, South Dakota, Wyoming, Nebraska, Colorado, Kansas, haveincreased over the pastfew years.We located27 recordsfor the Oklahoma,Texas, and New Mexico),but only the partsof thosestates GreatPlains (Table 1, Figure5; weexcluded a marinerecord from Texas). lyingeast of the ContinentalDivide. Thesedata indicate that Arctic Tern is a rarespring (14 May-20June; 9 records)and fall (11 July-14October; 16 records)migrant, with no evidenceof breeding.Two records(28 June in Montanaand 3 Julyin New Mexico)defy classification and couldrepresent late springmigrants, non-breeding birds A summeringsouth of the regularbreeding range, or earlyfall NORTH migrants.The only recordsof summeringbirds are from DAKOTA Montana(three records, this paper).It may be noteworthy that recordsfrom the easternpart of the GreatPlains tend to be in spring,while more westerlyrecords tend to be in A autumn. SOUTH DAKOTA Basedon the availableGreat Plainsdata, there wasno reasonto believethat breedingwas even remotely likely in the GreatPlains or, morespecifically, in Montana.First, the clos- est known breedinglocales to BowdoinNational Wildlife NEBRASKA Refugeare in PugetSound, Washington (approximately 1300 km to the west)and northern Saskatchewan (approximately 1350 km to the north). Second,all recordsfrom the summer monthsappear to be of migrantsthat remainedat a sitefor no RADO KANSAS morethan a few days,except for old breedingrecords from Wisconsin. co,o_I Onemay speculate that recordsof ArcticTerns in theGreat Plains will continue to increase as birders make a more con- certedeffort to find themduring migration. In the absenceof otherbreeding data from the Lower48 andadjacent southern MEXICO Canada,however, we see no reasonto expecta similarincrease in breedingrecords. How longArctic Terns continue to breed at thissite in Montanawill be a subjectof continuedinterest.

Acknowledgments We thankCharles R. Carlsonfor providingus with informa- tion froman 18June 1998 visit and helping us to identifythe possiblefish species in LakeBowdoin. David C. Ely andTim T. Hankshelped monitor the 1999nesting attempts and Aaron Aß springsummerrecord•'• record -• •.TEXAS f• Brees helped monitor the 2000 nestingattempt. James W. Arterburn,Peter Grant, Bill Howe,Bill Lisowsky,Ron Martin, • fallrecord • W. RossSilcock, and SartorO. Williams,III, helpedus locate ArcticTern records in the GreatPlains region. W. RossSilcock andMarshall Iliff carefullyread and edited the manuscriptof bgure5 Arc'dcTern records in lhe GreatPlains east ol lhe ContinentalDivide. thispaper and much improved it.

130 NORTH AMERICAN BIRDS ArcticTerns Nesting in Montana

Literature Cited American Ornithologists' Union. Table t. Records of Arctic Terns in the Great Plains 1998. Check-list of North (onlylocations east of theContinental Divide). American Birds, seventh ed. -- Date(s) F Number Location Reference AmericanOrnithologists' Union, Montana I ,, - ß Washington,D.C. 28 June1994 I adult LeboL., WheatlandCo. FieldNotes 415:957 Andrews,R., and R. Righter.1992. 14June-5 Augu• 1998 3adults BowdoinN.W.R., Philli sCo. FieldNotes 52:471, 518, this article Colorado Birds. Denver Museum 30 Ma -3 Au ast 1999 3 adults BowdoinN.W.R., PhiIll s Co. North AmericanBirds 53:294, this article of NaturalHistory, Denver, CO. Baicich, P. J., and C. J. O. Harrison. 1997.A Guideto the Nests,Eggs, and Nestlingsof North American Birds,second ed. AcademicPress, SanDiego, CA. Bent, A. C. 1963. Life Historiesof SOLOhDakota • North American Gulls and Terns. 16-17May 1999 1 adult Oahedam, Stanley/Hughes Co. North American Birds 53:294 Dover Publications Inc., New York, NY. 11July 1992 1 adult SodaL., Casper,Natrona Co. American Birds 46:1158 Conry,J. A., andB. E.Webb. 1982. An i4 October 1997 juvepilg.. YellowstoneNational Pa•k, Teton Co. FieldNotes 52:98 extant specimenof Arctic Tern from Colorado. Western Birds 13: -Nebrask• 37-38. 20 September2000 adult Lake Minatare, ScottsBluff Co. S.J. Dinsmore pers. obs. Cramp, S. 1985. The Birds of the Colorsrio ß WesternPalearctic, vol. 4. Oxford 16 Se ,tember 1912 1 adult Windsor,Weld Cc• Com andWebb(1982) UniversityPress, Oxford. 11•i•zSeptemb•r:•i979 f'l•dult '• •Unlon ReServoir',' We.iff, C• ' • Godfrey,W. E. 1966.Birds of Canada. 12 June1991 1 adult AdobeCreek Reservoir,Kiowa/Bent Co. Andrewsand Righter (1992) National Museum of Canada, 9 June1992 I adult Nee NosheReservoir, Kiowa Co. B. Liso••k 7 pets.comm. Ottawa. 20 September1997 1 iuvenile Lower Latham Reservoir,Weld Co. Field Notes 52:98 Kumlien, L., and N. Hollister. 1903. 5 October 1999 1adult t UnionReservoir, WeldCo. North American Birds 54:81 The Birds of Wisconsin. Bulletin 23September 2000 a 1adult / BigJohnson Reservoir, E1Paso CO. E Gent pers.comm. of the WisconsinNatural History 29September 2000 a I adult t PuebloReservoir, Pueblo CO. 5-11 October 2000a 1juvenile., I Union Reservoir, We!d•9' E Gentpers. comm. Society3: 1-143. 746:•ber 200{•.•, •'Goatperu. •: '• Montana Bird Distribution 2j"dveniles ,'dI •Chatfield ReserVoir,J•ffe•on CO .P.Gent pets. comm. Committee. 1996. P. D. Skaarg Kansas Montana Bird Distribution, fifth No records I ed. SpecialPublication No. 3, Montana Natural Heritage Oklahoma Program,Helena. 26May 2000 1adult Lak•Yaho!a?TulsaCo. ] NorthAmeric•nirds55:193 Olsen, K. M., and H. Larsson. 1995. 25September 2000 1juvenile , Lake.'O010gah, Rogers Go• "'1.J•A• Arterburr/-;i•ers.'comm. 10October 2000 1juvenile LakeHefner, Oklahoma Co. I J'W. Afterburn pers. comm. Terns of Europe and North America. Princeton University Press,Princeton, NJ. 14October 2000a 1adult LakfneHahoe,er ldO maCo• Robbins, S. D., Jr. 1991. Wisconsin 1 adult McNarv Reservoir,Hudmeth Co. Field Notes51:1021 Birdlife. The University of -7June 1997 Wisconsin Press,Madison. ewMexico ""•"?', • ---•2 • '• •:_ 7•== •- • Roberson,D, S.C. Rottenborn, S. B. 8September 1995 adult, 1juvenile Maxwell NWR,Colfax Co FieldNotes 50.94 .... Terrill, and D. S. Singer. 1999. July1997 1 adult ElephantButte L., Sierra Co. FieldNotes 51:1034, 1064 Middle Pacific Coast region. 5MaySeptember 1998 199•1 _I1juvenileadult I BrantleySantaRosa_ L.,Reservoir,Eddy Co. Guadalupe Co. jAmericanField Notes Birds 52:369,46:301 370 North American Birds 53: 428-43 I. a Pendingacceptance bythe states records committee. Robinson, J. A., K. C. Hamer, and L. S. Chivers.2001. Contrastingbrood sizes in Commonand Arctic Terns:The rolesof food provisioningrates and parentalbrooding. Condor 103:108-117. Veit, R. R., and W. R. Petersen.1993. Birds of Massachusetts. MassachusettsAudubon Society, Lincoln, MA.

--Received14 February 2001; Accepted 4 May 2001.

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