SPECIAL HABITATS Breeding birds in cedar stands in the Great Dismal Swamp Karen A. Terwilliger and Robert K. Rose HEGREAT DISMAL SWAMP, located on of 23 weeks of fieldwork between 1895 annualBreedingBird Surveysof Meanley in the Swamp. the coastal plain on the VirginiaNorthCarolinaborder,haslongbeenrecognizedasa vegetationallydistinctiveregion with many unusualgeologicaland biological features. Formerly at least twice the currently estimated size of ported the first Swainson's Warbler (Lymnoth(wis swainsonii)for theregion. 85,000 hectares(Carter 1979), the Great veys during this period, and Pearson, for study.Site I. calledthe Camp Site, DismalSwampis still shrinkingbecause of a droppingwatertablecausedby more than200 yearsof logging,ditching,and who later became director of the National wasa 7-hectarepatchof cedarssurrounded by maple-gumforest and located in Virginia. It survivedthe mostrecentlogging operationand is best describedas beingan overmature( = pastprime-timber growth) standwith an encroaching hardwoodmidstoryand a denseevergreenshrubunderstory(Fig. I). This is- other human activities. In 1973, the and 1898. Fisher (1895), in the first de- scriptionof birdlife in the Swamp, re- Palmer and Bartsch of the U.S. National Museum also conducted their faunal sur- AudubonSociety, conductedan unsuccessfulsearchfor the Ivory-billedWoodpecker(Campephilusprincipalis) then. Union Camp Corporationdonated a Little more was written about Dismal 19,871-hectare tract located near Suf- Swampbirdsuntil the 1930s. when Murray (1932) reported Virginia's first Wayne's (Black-throatedGreen) Warbler (Dendroicavirenswaynei) from the Swamp.Meanleyhas madethe greatest contributionto an understanding of Dismal Swampbirdswith hismonograph on folk, Virginia. to The Nature Conservancy, which transferredthe land to the U.S. FishandWildlife Service.This parcel, all in Virginia and including the 1255-hectare Lake Drummond, became thecoreof the Great Dismal SwampNational Wildlife Refuge (hereafter, G.D.S.N.W.R.), established in 1974. Swainson's Warbler (1971), The G.D.S.N.W.R. is still growing in size by the acquisitionof land by purchaseor by gift; by the end of 1980, it was 41,026 hectares,with 24 per cent (9866 hectares) in North Carolina. gum (Nyssasyh,atica) forest, have been Muchof the history,lore, and scientific investigationsof the Great Dismal Swamphave been summarizedby Kirk (1979), the resultsof a symposiumheld in 1974. In reality, few studiesof the made by Schwab (1979), Schwaband Gwynn(1980), and Gwynn (1981), and listsof birdsbreedingin standsof Atlantic White-cedar (Chamaecyparis thyoides)havebeenreportedby Terwil- ably greatly exaggeratedas an inducementfor peopleto settlethere(Handley 1979).The first descriptions of the nongame wildlife were made in a United AND METHODS WOCEDAR STANDS THAT differed in age, size, and locationwere selected landof century-old treesis surrounded by annual BreedingBird Surveys,and other notes and reports(1968, 1969, 1973, 1976, 1979). More recently, Breeding Bird Censuses in the dominantSwamphabitat, RedMaple(Acerrubrum)andBlack- DismalSwampbiotahavebeenattempted.Earliestreports of wildlifewereprob- MATERIALS liger (1981a, 198lb, 1982a, 1982b). This reportgivesdetailsof the breeding birdsin two cedarstandsand compares themto resultsof a three-yearstudyof the birds that breed in a stand of the domi- StatesGeologicalSurveyreport(Shaler nant maple-gumforest of the Swamp. Duringtwoyearsof study,sevenspecies 1890). Later, the United States (USDA) of birds were found to nest in cedar that Bureauof BiologicalSurveyssentcollectingpartiesintothe Swampfor a total did not use the maple-gumsite. These Figure I. The Camp site. Photo/Stephen D. species,however, were recordedin the Mallette. 24 American Birds.January-February 1984 an expanseof evergreenshruband maple-gumforest. Site 2, the ForestLine Site, wasa sample7-hectareplot located in the center of a dense 80-hectare stand of mature(70-year-old)timberwith little or no midstoryand a denseevergreen shrublayer. This site, locatedin North Carolina, is in a sectionof the Swamp with someof the largeststandsof uncut Atlantic White-cedar left in the United States.A third locality, the Maple-gum Site, was usedby Schwaband Gwynn, and has been describedin detail by Schwab(1979); it was certsusedin this studyfor comparativepurposes. two cedar stands, and these differences DISCUSSION wereconsistent betweenyears(Table 1). Besidesparulids, 11 families representingfour orders were recorded as breedingwithinstandsof AtlanticWhite- The Maple-gum Site supportednine speciesnot seenin the cedarstands(Ta- cedar (Table 2). By contrast,on the Maple-gumSite, Prairieand Worm-eatingwarblerswere not recordedduringany year of study, andtheabove-mentioned four speciesof parulids comprised 44 to 52 percentof the breedingbirdsduringeachyear. To Censuses were conducted between 0700 and 1100 hours from the first week an extent, thesetwo warblersmay have beenreplacedby the LouisianaWaterthrushand Blue-grayGnatcatchers.Besidesthe warblers,therewere 13 families from six ordersthat nestedin the maple- inAprilthrough thesecond weekinJune, gumforest(Table2). ble 1) andthe cedarsiteshad sevenspeciesthatdid not occurin the maple-gum forest. In the cedar standsonly two of thesesevenbirdsbelongto thesamefamily; therestarea diversegroup,overhalf of whichare sharedby bothcedarsites The cedarcommunitynot only supporteda higher numberof nestingspecies, but alsoa muchhigherdensity.In thethreeyearsof studyin themaple-gum forest,thedensities of 593/km2 in 1978, 623/km2 in 1979, and 613/km• in 1980 were about half the densities from the cedar sites. The cedar stand values were usingtheWilliamsSpotMap method(International Bird Census Committee 1970). To establishthe territoryof any breedingbird,thismethodrecommends a minimum of nine visits during which sightor soundcontacts ("registrations") are recorded for each bird. In order to spanthebreeding seasons of birdsknown to nestin theSwamp,eachcedarsitewas visitedtwiceweeklyduringthe I l-week studyperiod.Duringeachvisit, all terri- Table 1. Species andnumberof breedingbirdsobserved ontwocedarandonemaple-gum forest study sites,basedon the number of territorial birds, roundedto the nearest0.5 territory. For marginalterritorieshavinglessthan 25 per centof the territory within the studysite,a "+" wasassigned. A •*" referstospecies foundonlyin cedar;"**"refersto speciesfound only in maple-gum. Cedar Stands Site I 1980 torial birds, their nests, aggressiveen- counters,. and simultaneous registrations wererecordedon a mapfor eachspecies. In addition,the location,heightfit which it wasobserved,and generalactivityof Red-shouldered Hawk MourningDove Yellow-billed + Maple-gumStand Site 3 Site 2 1981 1980 1981 + + + 2 1978 + + each bird were recorded for each visit. DownyWoodpecker** Hairy Woodpecker** Informationon height,activity,anddensityof thebreedingbirdswill bereported elsewhere (Terwilliger and Rose, in PileatedWoodpecker RESULTS NTHECAMP SITE, 23and20species of birdswererecordedasbreedingin 1980and 1981, respectively,compared to 17 and 16 at the ForestLine Site (Table 1) For the Maple-gumsite, 22, 16• and 19 specieswere recoi'dedas breeding duringtheperiod1978to 1980(Tablel). Fhe cedarstandswere dominatedby warblers (Table 1), with Prairie, Prothonotary, Hooded and Worm-eating warblers, Ovenbirds, and Common Yel- lowthroats comprising 74 to 78 per cent + + + + 4 + 1 2 Great CrestedFlycatcher Blue Jay* 2 I 2 1 3 2 2 1 Carolina Chickadee Tufted Titmouse* 3 3 2 1 4 2 3 1 1 + Blue-grayGnatcatcher** Gray Catbird* I 1 3 Wood Thrush 2 1 5 2 3 White-eyedVireo Red-eyedVireo 2 3 2.5 3 2 7 4 3 I 3 4 1 4 13 10 Pine Warbler** Prairie Warbler* 18 17 19 15 ProthonotaryWarbler 18 15 4 3 Worm-eatingWarbler* 5 2 5 4 Swainson's Warbler Ovenbird Louisiana Waterthrush** 1 8 7 11 8 5 5 7 5 7 4 19 12 16 12 8 5 5 6 6 5 19 62 613 Corn. Yellowthroat Hooded Warbler both years. Interestingly,two warblers showedreciprocaldensitiesduringboth SummerTanager** N. Cardinal* years; ProthonotaryWarblers were far Rufous-sided Towhee morenumerous on the older Camp Site andCommonYellowthroatspredominat- ChippingSparrow** Volume38, NumberI 1 I of thebreeding birdsonbothsitesduring ed in the younger, more dense Forest Line Site. Consequently,the four most common speciesdiffered between the 1 2 1 I AcadianFlycatcher* Wren 2 + N. Flicker Carolina 2 1 3 Barred Owl** prep.). 1980 + + Cuckoo** E. Wood-Pewee 1979 3 13 + 2.5 10.5 + 1 1 4 2 + 2 TotalNo. Species 23 20 17 16 Total No. Individuals 88 73.5 95 74 22 60 16 63 1256 1035 1369 1042 593 623 Density perkm2 II 25 Table 2. Breedingbirds of the Dismal Swamp,groupedby order and family. For defini- tions of "+ ", "*" and "**", see Table 1. Cedar Stands Falconiformes Buteoninae + 1981 1980 sities, in the closed forest of the Dismal Maple-gumStand Site 2 Site 1 1980 Swamp. Prairie Warblers are normally Site 3 1981 + 1978 1979 associatedwith "open-countryplaces having high ground and few trees" (James1971). In a monographon the species, Nolan(1978) reportedthehigh- 1980 + est densities from such habitats. He also Columbiformes Columbidae Cuculiformes** Cuculidae 2 + + + 1 reportedthattheDismalSwampis oneof thefew locationsin whichthespecies has 2 been recorded in closed habitat. I 3 Strigiformes** Strigidae 2 + Onepossibleexplanation for the presenceof breedingPrairieWarblersin Disreal Swampforestslies in the historyof the species.Kendeigh(1961) believed + Piciformes 1 I Tyrannidae 3 4 3 3 Corvidae* Paridae 1 6 I 2 1 3 6 1 3 5 4 Picidae 1 2 2 2 11 7 3 4 1 4 3 3 6 6 6 Passiformes Troglodytidae + Mimidae* Turdidae 1 2 I 1 thatthespecies,whosecenterof distribution is in the Gulf and Atlantic States, wasoriginallyassociated with the southeasternpineor magnolia-oak forestsand theirseralstages.Mengel (1964) associatedthisspecieswith the Madro-temary sclerophyllous woodlandsand pine for- 2 3 1 Sylviidae** Vireonidae Parulidae 5 66 5.5 54 70 1 3 4 5 58 37 33 33 63 62 Thraupidae** ests.Bothauthorsagreethatthe dispersal of PrairieWarblersinto, and adaptation to, forest-edgeand deciduouscommunitiesprobablyoccurredduringthePleistocene. Man's activities in the past 200 + Fringillidae 1 Totals It is unclear why Prairie Warblers shouldbebreeding,andat suchhighden- 88 3 4 2 + 73.5 95 74 60 + yearshaveresultedin a dramaticchange Thus, the cedar stands are valuable re- clearthatsmallpatchesof overmaturecedarsurrounded by maple-gumforestpro- sourcesfor birdsnestingin the Dismal vide habitat that is as valuable for cedar- in the vegetationof the Dismal Swamp, and today large areas of cane, Baldcypress,and cedar are becomingincreasingly rare. In 1980, an estimatcd500 hectaresof pure and mixed cedarlorest nestingbirds as the interior of a large remain cedar stand. boundaries. Red Maple-Blackgum,now overwhelmingly dominantin theSwamp, is favoredby the drier conditionscreated over1000/km 2 duringbothyears(Table 1) andhadanaverage valueof 1175/kin 2. Swamp becausesthey not only accommodatea numberof speciesthat apparentlydo notbreedin the maple-gumforest, butbecausetheyalsosupportnearly twice the densityof birds found in the maple-gumforest. In 1981, thc average densityof the two cedar stands,1312/ replicatedstudies.Nevertheless,it is It is also clear that the loss of cedar as a habitattype will almostcertainlyinfluence the distribution and numbers of km2, wasthehighest valuerecorded for somespecies presently nestingwithinthe Swamp. Almost certainly Prairie Warblerswoulddisappearas breedingbirds thebirdsnestingin 12easternconiferous from the interior Swamp forests, al- forest habitats (Van Velzen 1981). In thoughthey would likely remainalong ditchedgesandin theearly regeneration fact, in 1981the densityof nestingbirds in theDismalSwampcedarstands( 1312/ km2) was 2.57 timesgreaterthan the average densitics (510/km :) ontheother 10 coniferous forest studies (Van Velzen 1981). The causesof thesehighdensities may be related to differencesin habitat structure, to be evaluated in detail in Ter- williger and Rose(in prep.). The older and isolated stand (Camp Site)hadmorespeciesthanwerepresent on the Forest Line Site. Whether this largernumberis due to the deterioration of the 100-year-oldtreesandtheresulting large number of holes, fallen trees and tangledsnags,to a betterdevelopedmidstory due to later encroachment of de- ciduous trees,or to a largeandbeneficial edgeeffectcannotbe determinedwithout 26 areaswherethey presentlybreed. However,theWorm-eatingWarblerwouldbe evenmoremarkedlyaffected,sincethey havenot beenreportedelsewherewithin the Swampexcept in small patchesof roesic hardwoods (Meanley pets. comm.).Exceptfor theGray Catbirdand TuftedTitmouse, which alsobreedin ce- darbutapparentlynotin maple-gum,the otherspecieswere presentat a frequency of one breedingpair or lessper year for each 7-hectareplot. These specieshave within the G.D.S.N.W R by a lowered watcr table. This studyhas revealedthat the cedar communitysupportsa much greateravlfaunathanpreviouslybelieved,at leastin the Dismal Swamp. In letters dated March 3, 1980 and April 24, 1981, Mcanley (pets. comm.) predicted "a sparsebirdlife with low diversity" in the dense cedar stands. Instead, cedar stands in theG.D.S.N.W.R. supportthehighest densitiesreportedfor any coniferousforcst censused in eastern North America during1981,andnearlytwicethedensity of birdsin the maple-gumforest. Seven speciesappearto preferthe cedarsitesto themaple-gumsitesfor breeding,implying that at least someof thesemight be affected if Atlantic White-cedar vanishes as a habitattype in the G.D.S.N.W R been shown to breed at low densities else- The U.S. Fish and Wildlife wherein theDismalSwampaccordingto the annual Breeding Bird Surveys of Meanley, but not in the censusesof SchwabandGwynnin the singlemaplegum site (1979, 1980, 1981). the Refuge recognizedthat the cedar communitymay be a distinctiveresource to wildlife, and that any management plan for the cedarstandsultimately also would affect the wildlife Service and there. AmericanBirds, January-February 1984 The primaryobjectiveol this study, then, was to determine the status ol breedingbirdsin the cedarstands,not only the densityof suchbirds but the possible kindsof birdsthatbreedonlyin cedar standswill only ensurethat 100 yearsfrom nowthe current500 hectares of cedarwill be a part, perhapseven an reit an assessmentof the cost (to wildlife indistinguishable part,of themaple-gum forestthatis comingto dominatetheDismal Swamp.Doing nothingis the same ascondemning thecedarstands to a rapid resources in the Refuge)of losingcedar decline. If the tentative forest manage- stands.The findingsof this studysupport the need for an effective management mentplancanbeimplemented, andif the planfor cedarstandsin the Refuge.In particular,this researchhas shownthe darstands to breeding birds.In consider- will be possible for otherinvestigators to learnwhy standsof AtlanticWhite-cedar supportsuchhigh densitiesof nesting birds,and why PrairieWarblersnestin ation of the demonstrated value of Atlan- these interior forests of the Dismal tic White-cedar to breeding birds, a Swamp. cedar stands.This information will per- value of both mature and overmature ce- burnsin the cut standsare successful,it the natural successional patterns" (A. Carterpets.comm.).Harvesting in strips hasbeenrecommended in preferenceto harvesting in largeblocks,because strips provide thegreater edge-to-area ratiothat will benefitbreedingbirds.However,in small cedar stands, blocks of small size (lessthan15hectares)wouldbe retained. These two harvestingmethodswould G D S.N.W.R., and help to maintain Prairie Warblers, Worm-eating Warblers,andseveralotherspeciesof birds that seemto breed in higher numbersin cedarstandsthanin the maple-gumforest Onemightaskwhyanyof thecedarin theRefugemustbeharvested, in viewof ACKNOWLEDGMENTS HISPAPER }Sderived in partfroma Master's thesis at Old Dominion Uni- versity. The study was conductedwhile theseniorauthorwasa Wildlife Biologist (Graduate Research position) for the U.S.F.&W.S.'s G.D.S.N.W.R.; M. Keel. The cooperation of theRefuge and U.S.G.S. staffs was appreciated. Thanks are due to the North Am. Birds 33:61-62. __ Carolina for access and scientific collection. mixed hardwoods. Am. Birds 34:49. SHALER, N. S. 1890. Generalaccountof the fresh-water morasses of the United States, with a descriptionof the Dismal Swamp district of Virginia and North Carolina. U.S. Geol. Surv., Ann. Rpt. 10:255-339. TERWILLIGER, K. A. 198la. Breedingbird census in Atlantic white cedar. Am. Bird• 35:68-69. Fi- nally, many thanksto Brooke Meanley for his correspondence and his willingnessto sharehis knowledgeof Dismal Swampbirds. and T. M. GWYNN, I11. 1980. Breed- ing bird censusin red maple-blackgum State Park Service for their permission __. 1981b.Breedingbirdcensusin Atlantic white cedar stand. Am. Birds 35:69. __. 1982a.Breedingbirdcensusin Atlantic white cedar. Am. Birds 36:73. __. 1982b.Breedingbirdcensus in Atlantic white cedar. Am. Birds 36:73. VAN VELZEN, W. T. 1981. Forty-fourth breedingbird census.Am. Birds 35:47. tionsto the DismalSwamp.pp. 80-100 In The Great Dismal Swamp, P. W. Kirk, Jr., ed., UniversityPress of Virginia, Charlottesville,427 pp. FISHER, A. K. 1895. Occurrence of Helinaia swainsoniiin the DismalSwamp,Virginia. Auk 12:307. GWYNN, T. M., 11I. 1981. Breeding bird census in red maple-black gum mixed hardwoods. Am, Birds 35:55. HANDLEY, Volume38, NumberI 595. SCHWAB, D. S. 1979. Breedingbird census in redmaple-blackgummixedhardwoods this supportis gratefullyacknowledged, with specialthanksto RefugeManagerRalph species, andwill eventually be replaced sion, probablyby southernevergreen shrubs, withRedBay((Perseaborbonia) beingoneof thedominants. But moreto the point,in the DismalSwampwhere thewatertablehasbeendroppingfor decades,cedarstandswill be replacedby mapleandgumtrees,suchasis happenlngon the 100-year-old CampSite now. Consequently, a forestmanagement plan thatcallsfor the preservation of existing 3:9-43. havior of the Prairie Warbler (Dendroica The fact is that cedar is a fire sub-climax in thenormalcourseof biologicalsucces- Swampbirds. Raven44:3-4. 1976. A censusof breedingbirds in the Dismal Swamp, Va. Raven 47:40-43. __. 1979.An analysisof the birdlife of the DismalSwamp.pp. 261-276In The Great DismalSwamp, P. W. Kirk, Jr., ed., University Pressof Virginia, Charlottesvile, 427 pp. MENGEL, R. M. 1964.The probablehistory of speciesformation in some northern wood warblers (Parulidae). Living Bird __. discolor). Ornithological Monogr. 26:1- JAMES, F. C. 1971. Ordinationsof habitat relationshipsamong birds. Wilson Bull. its demonstrated value to breedingbirds. N. Amer. Fauna. 69:1-90 Additional notes on Dismal NOLAN, V., JR. 1978. The ecologyand be- providethe seedtreesfor the potential regeneration of the cedarthathadbeen CITED harvested on nearbyplots.If successful, LITERATURE thisplanwill permitthe probableretenCARTER, V. 1979. Remotesensingapplication of cedar as a resource within the 1973. 49:487488. G D S.N.W.R. has emphasizedthe im- means of providing "ageclassdiversity, higherbird speciesdiversity,research naturalareas,greateraesthetic andpublic usevalue,andstudyareasfor observing 1971. Natural History of the Swainson's warbler. MURRAY, J. J. 1932. Wayne's warbler, an addition to the Virginia avifauna. Auk tentativeforestmanagement planfor the portance of an age-class diversity.Furthermore,thetentativeplancallsfor the preservation of old-growthstands(over 100yearsof age)to comprise at least10 per centof the total area of cedaras a 1969 Notes on Dismal Swamp birds Rm,en 40:47•,9. 83:215-236. Wommissionof Gameand Inland Fisheries, P.O. Box 11104, RichmondVA23230 (Terwilliger), Departmentof BiologicalSciences, Old Dominion Universi.ty, Norfolk, VA23508 (Rose) C. O., JR. 1979. Mammals of the Dismal Swamp:A historicalaccount. pp.;297-357In The GreatDismalSwamp, P. W. Kirk, Jr., ed., University Pressof Virginia, Charlottesville,427 pp. KENDEIGH, S.C. 1961. Animal Ecology. Prentice-Hall,Inc., Englewood Cliffs, New Jersey,468 pp. KIRK, P. W., JR. 1979. The Great Dismal Swamp. University Press of Virginia, Charlottesville,427 pp. MEANLEY, B. 1968. Birdsof theGreatDis- mal Swamp.AtlanticNat. 23:141-142. 27
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