Observations on Rufous necked Aceros nipalensis and Austen's Brown Hornbills in Arunachal Pradesh: natural history, conservation status and threats

108 Indian Birds Vol. 5 No. 4 (Publ. 15th October 2009)

ObservationsonRufous-neckedAceros nipalensis and Austen’s Brown Anorrhinus austeni Hornbills in

ArunachalPradesh:naturalhistory,conservationstatus,and threats

Aparajita Datta

Datta,A.2009.ObservationsonRufous-neckedAceros nipalensis and Austen’s Brown Anorrhinus austeniHornbillsinArunachalPradesh:naturalhistory,conservationstatus,andthreats.Indian Birds5(4):108–117.

AparajitaDatta,NatureConservationFoundation, 3076/5, 4thCross,GokulamPark,Mysore 570002,Karnataka, India.Email:[email protected].

In 1997–1998, Ravi Sankaran had spent three months studying the most interesting, and intriguing, hornbill species found in India, with the smallest global range—the Narcondam Hornbill Acerosnarcondami—restricted to a 6 km2 island of the Andaman Islands archipelago. While others before him had spent time on the island and made observations, his were the first systematic and meticulously collected data of a study carried out throughout the breeding season, on a large number of nests. Unfortunately, he never wrote up the work as a publication, but he put his research to good use for conservation action and managed to get the goats that were affecting the regeneration of many hornbill food plants, removed from the island. My paper, in this memorial issue, is about my limited observations on two of the lesser-known, and threatened hornbills of north-eastern India.

AbstractAmongthefivespeciesofhornbillsthatoccurinnorth-easternIndia,theleaststudiedarethe

endangeredRufous-neckedHornbillAceros nipalensis, and the Brown Hornbill Anorrhinus austeni1,whichhasarestricteddistributioninIndia.BasedonfieldsurveysconductedinNamdaphaNationalPark,andseveralforestdivisionsineasternArunachalPradesh,during1996–1999and2002–2004,Ipresentinformationontheirdistributionandrelativeabundance.Ialsopresentsomeinformationondiet,flock

sizes,canopylevelsused,breedingbiology,andnestingrecordsforboththesespecies.

IntroductionIndiaishometoninespeciesofhornbills(Bucerotidae).Apartfromthe Great Hornbill Buceros bicornis, andOrientalPiedHornbillAnthracoceros albirostris,whichalsooccurinotherpartsofIndia,three species—WreathedAceros undulatus, Rufous-neckedA. nipalensis, and Austen’s Brown Anorrhinus austeniHornbills—occurinnorth-easternIndia.

Collar et al. (1994) listed ten globally threatenedhornbillspecies,ofwhichtwooccurinIndia,theRufous-necked,andtheNarcondamA. narcondami Hornbills, whilethree—MalabarGreyOcyceros griseus, Malabar Pied A. coronatus, and Austen’s Brown Hornbills—arelistedas‘nearthreatened’.Allthesespeciesalsohaverestricteddistributions.

Among the species occurring in north-eastern India, theRufous-neckedHornbillislistedas‘vulnerable’byIUCN(2006),whiletheGreatandAusten’sBrownHornbillsarelistedas‘nearthreatened’IUCN(2006).ThetwomainfactorsthataffectAusten’sBrownandRufous-neckedHornbillsinnorth-easternIndiaarehunting and habitat loss.

The two Aceros speciesaremorewidelydistributedwithinnorth-eastern India than the smaller, co-operativelybreeding,Austen’sBrownHornbill,which is restricted toupperAssamandeasternArunachalPradesh,southofRiverBrahmaputra.ThecurrentdistributionofAusten’sBrownHornbillisinadequatelyknownand the factors responsible for its localisedoccurrence

within north-eastern India, and its present rarity,would beinterestingtodetermine.Itisuncommonindeciduousforestandlocallycommoninevergreenforest(Ali&Ripley1987),andwasreportedtobeverycommon,about80yearsago,intheplainsofeasternAssam(Baker1927).Chowdhury(2000)providessightingrecordsinvarioussmallreserveforestpatchesineasternAssam,Manipur,andNagaland.Pawar&Birand(2001)havealsoreporteditsoccurrenceintheBarailRange.

Huntingofallhornbillspecies,bymosttribalcommunities,isamajorthreat,andaprimarycauseforhornbilldeclineinmanyareas.Thebreedingbiology,nestsiteselection,diet,androostingpatternsof theGreat,Wreathed, andOrientalPiedHornbills,and their functional roleas seeddispersershavebeen studiedinArunachalPradesh (Datta2001;Datta&Rawat2003, 2004).However, there is limited informationon thenatural history,breedingbiology, anddietof theRufous-neckedandAusten’sBrownHornbills, in India, apart fromanecdotal observationsthat breedingoccurs betweenMarch and June (Ali&Ripley1987),although therehavebeen long-termstudies inThailand(Poonswad1995;Poonswadet al.1987,1988,1998;Poonswad&Tsuji1994;Chimchomeet al. 1998).

In this paper, I present information on diet, flock size,habitat use, distribution, andnesting ofRufous-necked andAusten’sBrownHornbills,collectedbetween1996and2004 ineasternArunachalPradesh.Thethreatstothesespecies,duetocurrenthabitatloss,andhuntingpractices,arealsooutlinedanddiscussed.1 Rasmussen&Anderton(2005)placeitinthegenusPtilolaemus.

109Indian Birds Vol. 5 No. 4 (Publ. 15th October 2009)

Survey areas N a m d a p h a N a t i o n a l P a r k (NamdaphaNP; 27°23’–27°39’N 96°15’–96°58’E): locatedineasternArunachal Pradesh, Changlangdistrict, comprises an area of1985 km², with a wide altitudinal variationfrom200mtoover4500m at Dapha Bum, the highestpoint in thepark. Thevariety ofhabitats found here, ranging from temperate,subtropical,andtropicalrain forests, has facilitated thepresenceofadiverseandrichfauna.TheKamlangWildlife Sanctuaryborders it on the north. To the south and south-east lie high mountain ranges and the international border with Myanmar. There are many smallstreamsandriversthatdraininto the Noa-dihing, a tributary of theBrahmaputra,flowing easttowest through the park. It iscontiguouswith reserve forestsand sanctuaries to the south andwest. Towards the eastern boundary there are community forests inVijaynagar circle (637 km2). Thearea ispopulatedbyanumberof

communities:Singpho, Tangsa, Chakma, and others, to the west of thepark,andLisu and Nepali,totheeast(Datta2007).Kamlang Wildlife Sanctuary (KamlangWS;786km2;27°40’N–28º0’N96°20’E–96°55’E): lies to thenorthofNamdaphaNP, inLohitdistrict.Ithassteepmountainousterrain,andiscriss-crossedbynumerousriversandstreams,withsomehighaltitudelakes.Thealtitudevariesfrom550mto4200m.ThefloralandfaunalspeciescompositionisbelievedtobesimilartothatofNamdaphaNP,althoughnoresearchhasbeenundertakenhere.Tothesouthof Kamlang WS, are lowland forests under the Namsai Forest Divisionwith several reserve forests (RF)—Turung,Kamlang,Tengapani,Manabum,andunclassedstateforests(USF).ThemaintribalcommunitiesherearetheMiju Mishmi, and the Khampti in thelowerareasofthedistrict.Jairampur Forest Division (JairampurFD;27°–27°40’N95°–97°E):comprises sevenRFareas thatare interspersedwithpatchesofcommunityforests,cultivation,andvillages.Theareacoveredbythe reserve forests is307km2.These forestswereoperated fortimber, mainly for hollong Dipterocarpus macrocarpus, and mekai Shorea assamica, till 1996,when timber extractionwasbanned,although someextractionoccurredup to 2000.The remainingareasareUSF,wherevillagerspracticeshiftingcultivation.ThelegalstatusofUSFareasisnotdefined.TheyaresimplydesignatedasanyforestthatisnotincludedinRFsandvillageforestreserves.Thereisnospecificlegalprovisiongrantingrightsandconcessionstolocalpeopleforcollectionfrom,oruseof,theseforests,yetitisacustomarytraditionandfulfilslocalpeople’sneeds.Noneofthemarenotified.ThereisnolandtenuresystemandthegovernmentdoesnothaveanyrightsoverUSF/communityland.PartsoftheRFsherearealmostundisturbedforests,especially towards theMyanmarborder.Theareahastropicalevergreenforests,dominatedbythetwocommerciallyimportantdipterocarpspecies.Theareahas28villages,withanestimatedpopulationofc. 6000. The main tribe here

AmaleRufous-neckedHornbillAceros nipalensis (about2yearsold)inNamdaphaNationalPark.

Datta:Rufous-neckedandAusten’sBrownHornbillsPh

oto:

Apa

rajit

a Dat

taPhoto: Rohit N

aniwadekar

Austen’s Brown Hornbill Anorrhinus austeniinloggedforestineasternArunachal.


is the Tangsa,whichisdividedintonumerousclansandsub-tribes.Deomali Forest Division (DeomaliFD;305km2;26°55’N–27°15’N95°10’–95°40’E):inTirapdistrict.ComprisesUSF,andfivevillageforestreserves(VFR;368km2).MostofthearealiesinthePatkaiHills, with hilly and undulating terrain, with altitude ranging from140mto1,410m.Theriversflowfromsouthtonorth;anddrainintotheBrahmaputrainAssam.Theforesttypesintheareaincludetropicalwetevergreendipterocarpforests,semi-evergreenforests,wetbamboobrakes,andpioneerEuphorbiaceaescrub.Themain tribes here are the Nocte and Wancho that inhabit the north-easternandsouthernparts,respectively,ofthedistrict.Thereare63villagesherewith5,178housesand26,360people.Villagesizesarecomparativelylargerangingfrom24to149households.Tirapdistricthasthehighestpopulationdensityinthestatewithanincreasefrom36perkm2 in1991to42perkm2 in2001.Livestockholdingsarealsorelativelyhigh.Themainoccupationhereisagriculture,mostofthelandintheupperNocte and Wancho areas is under jhum cultivation,andmanyareasareseverelydegraded,asfallowcyclesareshort.UntiltheSupremeCourtbanin1996,timberextraction,primarilyoftwodipterocarpspecies,wascarriedoutextensivelyinthelowerareas.Teaestateshavealsocomeupinthisdistrictoverthepast15years.

MethodsRelativeabundanceofhornbillswasassessedbywalkingtrailsintheforestsofRimaandPangsuRFsinJairampurFD(AprilandNovember2002),Changlangdistrict,whileMiaoRFwasvisitedforfourdaysinApril2002.TurungandKamlangRF,nearKamlangWS,andMopayaVFRinDeomaliFD,werealsovisitedinApril2002.Rains, and the lackoffieldguidespreventedaccessandexploration insideKamlangWS.During severalfieldvisits toNamdaphaNP(1996–2004),allsightingsofRufous-neckedandtheBrownHornbillswererecorded.Distanceswalked,andeffortputin(intermsofdaysspentwalking/searching),wererecordedtoobtainacrudeestimateofrelativeabundance.Encounterrates(numbersperkm)ofhornbillsarecomparedbetweenNamdapha(a protected area) and theRF/USF areas (unprotected).Onsightingoneofthetargetspecies,theflocksize,flockcomposition,canopy level,activity, if feeding, the foodspecies, locality,andhabitattypewererecorded.

A total of 74dayswere spent (walks, active searches) inNamdaphaNP,overseveralyears(April1996,November1997,November 1998,March 1999,October 1999,December 2002–January2003,October2003,andApril–May2004).ShortsurveyswerealsocarriedoutinRFstowardsthesouth-westernpartofthepark inMiaoReserveForest (RF),PangsuandRimaRFs,JairampurFDinApril–May2002and,November2002.ForestsnearKamlangWildlife Sanctuary (WS) and adjoiningRFs inLohitdistrictand,DeomaliinTirapdistrictwerealsovisitedinApril–May2002(Table1).AdditionalinformationfromKhonsaFDinTirapdistrict,visitedin1997,isalsoprovided.InformationaboutRufous-neckedHornbilldistributionisalsopresentedfromEagleNestWS,DoimaraRF,PapumRF,andcommunityforestsinEast,andWestKamengdistrictsinwesternArunachalPradesh.Fig.1depicts the forestareas,andsomeof thevillagesvisitedduringthefieldsurveysineasternArunachal.

ResultsDistribution and sighting records Rufous-necked Hornbill: Thespeciesisvulnerable,althoughnotcriticallyendangered,butfaceshighriskofextinctioninthewildinthemedium-termfuture(IUCN2009).Itisrareinmostpartsofitsglobalrange,thoughinBhutanitismorecommon.InIndia,populationsaremainlyfoundinArunachalPradesh,althoughitisalsoreportedfromSikkim,andnorthernBengal,intheeasternHimalaya.

Itisrareinmostpartsofnorth-easternIndiaduetohuntingandhabitatloss—itsstatusbeingbetteronlyinsomeprotectedareas ofArunachal Pradesh. In easternArunachal Pradesh,its status is better inNamdaphaNPand in forests above800m elevation, and inwesternArunachalPradesh inEast, andWestKamengdistricts aroundEagleNestWS and in higherareasofPapumandDoimaraRFinKhellongForestDivision.ItalsooccursinMehaoWS(DibangValleydistrict),andTaleWS(LowerSubansiridistrict),althoughitisrelativelyuncommon.InNamdaphaNP,itiscommonlysightedevenatlowerelevations(200–900m).Itisheavilyhuntedbyseveraltribes(Nishi, Wancho, Tangsa, Mishmi, Adi, and Apatani),especiallyinhigherelevationsub-tropical evergreen forests,where theGreat andWreathedHornbillsarelesscommonlyseen.Forestlossispossiblyalesserthreatforthisspecies,becausetheconditionandextentofforestsathigherelevationsarerelativelybetterthaninthefoothills;huntingmaybeamoreseriousproximatethreattothisspecies.

I had 101 sightings ofRufous-neckedHornbills between1996and2004(Table1).MostweresightedinNamdaphaNP(91sightings),whilesevensightingswereinRFs(RimaRF,PangsuRFinJairampurForestDivisionineasternArunachal,andDoimaraandPapumRF,KhellongForestDivision,westernArunachal),andthreeincommunityforests(alsodesignatedasUSFsinArunachal)intheVijaynagararea,Changlangdistrict.Austen’s Brown Hornbill:Itsglobalrangeisnorth-easternIndia,Myanmar, Thailand, Laos,Vietnam, and southernChina. ItsdistributioninIndiaisrestrictedtoeasternArunachalPradeshandAssam.AccordingtoAli&Ripley(1987)itmayoccurorhaveoccurredinManipurandNagaland;morerecently,Chowdhury(2000)hasreporteditsoccurrenceinthesetwostates.Ithasbeensighted fromareas inUpperAssam in JoypurRF (KashmiraKakati, pers. comm.),Tinsukiadistrict,intheCacharHills(Pawar&Birand 2001), and from several otherRFs inupperAssam(Chowdhury2000).

Ihadatotalof31sightingsofAusten’sBrownHornbilloverseveralvisitsbetween1996and2004(Table1).CallswereheardinMopayaVillageForestReserve,DeomaliForestDivision.Only

Fig.1.MapshowingsurveyareasinNamdaphaNationalPark(greenlinedepictsparkboundary)andJairampur,Deomali,LohitFD.Villages/townsvisitedduringthesurveyaremarkedascircles,whileotherlocations/campsinsideNamdaphaaremarkedwithsquares.Theyellowlinedepictsthe

international boundary with Myanmar.

Datta:Rufous-neckedandAusten’sBrownHornbills


twosightingswereinMiaoRF,whiletherestwereinNamdapha.ThespeciesisalsopresentinJairampurFD,aswasevidentfromskullsandheadsseenwithhuntersinthevillages.Althoughitwasnot sighted inKamlangWSandadjoining reserve forestsinLohitdistrict,reportsfromlocalvillagerssuggestthatitmayoccurthereandispossiblythewestern-mostdistributionlimitofthisspecies.EarlierreportsofthishornbillinArunachalPradeshwereonlyfromNamdapha(Singh1995).

Relative abundanceRelativeabundanceofhornbillswasobtainedfromtrailwalksinthesurveyareas.Intrailswalksbetween1996and1999(totaldistance357km,pooledoverseveralvisits,whichincludes112kmwalkedfromDebantoVijaynagar),wecounted162and123individuals ofRufous-neckedandAusten’sBrownHornbills,respectively,withanaverageencounterrateof0.32/km(±0.49)forRufous-necked, and 0.39/km (± 0.27) forAusten’sBrownHornbill.

Infield surveysbetween2002and2004 (totaldistance326km,which includes230km (twowalks fromMpen/Deban toVijaynagar),wecounted55Rufous-necked,and29Austen’sBrownHornbills,withanaverageencounterrateof0.28/km(±0.32)and0.29/km(±0.29),respectively.

There appears tobe a considerabledifferencebetween thebreedingandnon-breedingseason innumbersofboth speciesseeninthelow-andmid-elevationforests(200–1000m)(Fig.1),

withconsistentlyfewersightingsandnumbersinthenon-breedingseason(winter)forbothspecies.However,thiscouldalsobeduetothefactthatmostofthesurveyeffort,inthebreedingseason(allyears),wasintheDeban–Haldibari–Hornbill–Ranijheelarea,while in the non-breeding season, more effort was along the main Noa-dihingvalleyon theway toGandhigram–Vijaynagar.Ontheotherhand,theWreathedHornbill,whichisknowntomakelong-distancemovements,isseenintheareainlargeflocksinthenon-breedingseason(winter)(Table1).

Encounterratesofhornbillswereconsiderablylowerinreserveand community forests in Jairampur,Deomali, andLohitFDs(totaldistancewalked,133km,inApril–May2002).Threespecies,Rufous-necked,Austen’sBrown,andOrientalPiedHornbillsweresighted;callsofGreat,andAusten’sBrownHornbillswereheardonce.Therewerethreesightingsofsevenbirds[Brown,Rufous-neckedandWreathedhornbill].TheRufous-neckedhornbillwasvery rare inadjoining reserveandcommunity forests it (0.004birds/km±0.01).However,muchofthesurveyinthereserveandcommunity forestswas in low-elevation forest,whereRufous-neckedHornbillsgenerallydonotoccur.Austen’sBrownHornbillencounterrateswerealsolow(0.2birds/km±0.6).

Anadditional 116km (15days)werewalked in JairampurFDinNovember2002duringasurveyfor the leafdeer(Dattaet al.2003),duringwhichallhornbillsightingswerenoted.Twospecies—WreathedandRufous-neckedHornbills—weresighted,atotalof27individualsfrom10sightings.

Area Year Days spent Locations Effort

(kmwalked)Number (species)

Sightings/calls(totalnumbersseen)

NamdaphaNP April1996 3 Deban-Bulbulia, 17-19 mile MV road 37 2(RNH,BH) 7(24),1call

NamdaphaNP November1997 3 Deban-Bulbulia, 17-19 mile MV road 37 3(RNH,BH,WH) 8(54)

NamdaphaNP/Vijaynagar USF November1998 9 Deban-Vijaynagar 112 2(RNH,WH) 24(143)

NamdaphaNP March1999 15 Deban-Firmbase(varioustrails) 126 4(RNH,BH,WH,GH) 85(248),4calls

NamdaphaNP October1999 3 Deban-Hornbill, 17-19 mile MV road, Deban-Mpen 41 3(BH,WH,

GH) 13(42)

NamdaphaNP December2002 10 Deban-80 mile 102 1(WH) 2(23)

Vijaynagar USF December2002 15 80 mile -Gandhigram-Vijaynagar 28 2(RNH,WH) 8(32)

NamdaphaNP April2003 7 Deban-Bulbulia, 17-19 mile MV road ca.40 3(BH,GH,RNH) 14(23+)

NamdaphaNP October2003 7 Mpen-Gandhigram 128 1(RNH) 2(9)

NamdaphaNP April2004 7 Deban-Ranijheel, 17-22 mile MV road ca.56 3(BH,GH,RNH) 22(55)

JairampurFD November1998 1 HongkapRF 14 None —

JairampurFD April2002 4 Rima, Pangsu and Miao RF 59 2(BH,RNH) 2(5)

JairampurFD November2002 15 Nampong-Rima-Putok-Changlai-Tengpum 116 2(RNH,WH) 10(27)

*KamlangWS&Namsai FD May 2002 4 KamlangWS,Turung&KamlangRF 34 None —

DeomaliFD,JoypurRF April2002 5 MopayaVFR,JoypurRF 40 3(BH,GH,

OPH) 1(2),3calls

Poorweatherhamperedfieldworkandonlytheedgeofthesanctuarywasvisited(about7kmalongthetrailtoGlaolakefromWakro).MosttimespentinareasnearWakrotownandTurungRF.Abbreviations:BH=Austen’sBrownHornbill;GH=GreatHornbill;OPH=OrientalPiedHornbill;RNH=Rufous-neckedHornbill;WH=WreathedHornbill.

Table 1. hornbill records in areas surveyed between 1996 and 2004 (effort in terms of days spent and distances walked) in eastern Arunachal Pradesh



Flock sizesRufous-neckedHornbillsweremainly seen in pairs (45%ofsightings).Only3%ofsightingswereofbirdsinbiggerflocks(>10birds),mostlyatlargefruitingtrees.Austen’sBrownHornbillwasmostlyseeninflockscomprisingmorethanthreebirds(70%ofsightings).Themaximumflocksizewas15.Therewereonlyfoursightingseach,ofsinglebirds,andofpairs.

ThemeanflocksizeoftheRufous-neckedHornbillwas2.36birdsinthebreedingseason,whilethemodalandmedianflocksizewasone(n=85sightings).Themean,median,andmodalflocksizewastwointhenon-breedingseason(n=15sightings).Themaximumflocksizeseenwas19birdsinthebreedingseason,and 7 in the non-breeding season.

ThemeanflocksizeofAusten’sBrownHornbillwassixbirdsinboththebreeding(n=22),andnon-breedingseasons(n=5).Themedianandmodalflocksizewasfourinthebreedingseason,whileinthenon-breedingseasonmedianandmodalflocksizewastwoandonerespectively.

Use of canopy levelsAusten’sBrownHornbillusedallcanopylayersequally,whileRufous-neckedHornbillsweremostlysightedintheuppercanopylayer(71%ofsightings)(Fig.3).Thisdifferenceintheuseofcanopylevels is probably related to theirdiet and foraging strategy.WhiletheRufous-neckedHornbillislargelyaresident(possiblyterritorial) frugivore feedingoncanopyfruits,Austen’sBrownHornbillismoreomnivorousinitsdiet(Poonswadet al. 1986),feedingmuchmoreonanimalmatter,whichprobablyreflectsinitsuseofallcanopylayers.

DietLimitedobservationsonthedietofthetwospeciesweremadeduringwalks. In addition, regurgitated seeds,droppedbelowtwonestseach,ofbothhornbillspecies,wererecorded.Sixteenspecieswererecordedinthedietofthetwohornbills,11non-figfruitspecies,andfivefigspecies(Table2).

TheRufous-neckedHornbill is largelyfrugivorous,feedingmainlyonberries,drupes,andcapsularfruitsofprimaryforestspecies belonging to Lauraceae,Meliaceae,Myristicaceae,Annonaceae,andfigs(Moraceae).Noanimalmatterwasrecordedinitsdietintheselimitedobservations;howevermoredetailedstudiesinThailandsuggestthatitalsoconsumesanimalmatter,especially crabs (Chimchome et al. 1998).Basedon33 feedingobservations,thedietoftheRufous-neckedHornbillwasmadeupoffigsandnon-figfruits.51%observationswereonfigfruits(four species), and48%onfivespeciesofnon-fig fruits.Apartfromthis, regurgitatedseedsof fournon-figfruitspecieswererecordedbelowfruitingandperchtreesvisitedbyRufous-neckedHornbills.Fromanoldnest,severalotherspeciesinthedietofthese birds—Horsfieldia kingii, Polyalthia simiarum, and beetle remains—weredeciphered.Attwoactivenestsin2004,fivenon-figfruitspecieswererecorded.

Austen’s BrownHornbillswere recorded feeding onfigsandripefruitsofBeilshmediasp.duringsixsightings.TheywerealsoobservedinApril2002,deliveringfruitsoffivespeciesatanactivenest.TherewereregurgitatedseedsofPolyalthia simiarum, Dysoxylum binectariferum, Aglaiasp.,Horsfieldia kingii, and of some Lauraceae species, apart fromdefecations of fig seeds belowthenest.Austen’sBrownHornbillissupposedtohaveamixeddiet, but is largely insectivorous.Apart fromberries, drupes,capsularfruitsofprimaryforestspecies—Lauraceae,Meliaceae,Annonaceaeandfigs(Moraceae)—theyarereportedtoconsumearthropods,mollusks, and small vertebrates (Poonswad et al. 1986,1998).

Breeding season & nesting records Rufous-necked Hornbill: The breeding season of the Rufous-neckedHornbillinNamdaphaNPcommencesinlateApril,muchlaterthanthatofGreat,Wreathed,andOrientalPiedHornbillsfurtherwestinPakkeNP,wherenestingcommencesbyearly-tomid-Marchinmostyears(Datta2001;Datta&Rawat2004).

InMarch1999,Ispent15daysinNamdaphaNP,searchingfor active hornbill nests in theDeban–Haldibari–Hornbill–Bulbulia–Ranijheel–Firmbasearea.Noactivenesttreescouldbelocated.ItislikelythatnestingofRufous-neckedandAusten’sBrownHornbills hadnot commenced inmid- to late-March,becausetheformerweresightedinpairstilltheendofMarch,andcourtshipfeedingwasobservedduringthesecondandthirdweeksofMarch.AnoldnestoftheRufous-neckedHornbill,incommunity forestsnearKathangvillage (10km fromDeban)outsideNamdaphaNP,waslocatedwiththehelpofaMiju Mishmi villageheadman.Thenesthadapparentlybeendiscoveredtwoyearsagoandwasusedthepreviousyear,asevidentfromoldfeathers,seeds,andseedlingsofthehornbill’sregularfoodplants.The nest was on a Terminalia myriocarpa(Hollock)tree,adjacentto a jhumfield.ThevillageheadmanalsoinformedthatRufous-neckedHornbillsdonotstartnestingtillApril.However,therewasnonestingonthistreewhenitwassubsequentlycheckedinAprilandMaythatyear.

IwasalsoshownanoldnestofaRufous-neckedHornbillincommunityforestsnearPakke-ke-Sanghvillage,byaNishi hunter, at1,500m(EastKamengdistrict)onanAltingia excelsa(Jutuli)treeinJanuary2000.Pakke-ke-SanghvillagewasaccessedonfootfromSeijusa(PakkeWS),overatwo-daytrek(ca. 83km).

Fig.2.Mean(±SD)Encounterrates(nos/km)oftwohornbillspeciesinbreeding(n=313,effort:246km),andnon-breedingseason(n=55,effort:

437km)intheNamdaphaNationalPark.

Fig.3.UseofcanopylevelsbythetwohornbillspeciesinNamdaphaNationalPark,ArunachalPradesh.n=13sightingsforBH,59sightingsforRNH.



Intensive searches for nestswere carried out again inNamdaphainMarch–April2004.However,duringthisperiod,mostsightingswereofbirdsinpairs,indicatingthatmostbirdshad still not commencednesting.Despite the abundance ofsuitablecavities,mostbirdshadnotstartednestingevenbythelastweekofApril.TwoactivenestswerelocatedinthethirdweekofApril,inNamdapha.OnewaslocatedonaTerminalia myriocarpa treenearHornbillcampon26April2004.Ithadprobablybeenactivesinceaweek.Anotherwasfoundonasteepslope,downhillfromthe19thmile(oftheMiao–Vijaynagarroad),on24April2004.Itwaslocatedonatall,emergentA. excelsa.

Subsequently,inMay2004,anothernestwaslocatedinMiaoRF (AkhiNathany,pers. comm.). TheRufous-neckedHornbillappearstoberesidentandterritorial(mostlysightedinpairsinparticularlocalities),andthebreedingseasonisbetweenAprilandJuly/August.Unfortunately,thesenestscouldnotbemonitoredthroughout thebreeding cycle, as it coincideswith theperiodofheavyrainsintheareaandboththesenestsweredifficulttoaccess in themonsoon.Thus, there isneither any information

ontheexactexitdatesfromthenestnorwhetherthenestswereevensuccessful.

Austen’s Brown Hornbill: During intensive nest searchesinsideNamdaphainMarch1999,nonestsofthisspeciescouldbelocated.Thebirdsweremostlysightedinflocks.DuringthesurveyinJairampurFDin2002,aflockwassightedvisitingandfeedingatanactivenestinMiaoRF.AnestofAusten’sBrownHornbillwas shown to me by a Wanchoyouthon21April2002inMiaoRF.ThenestcavitywaslocatedonanAilanthus grandis (Borpat)tree,approximately1kmfromMiaotownship,onasteephillside,near aperennial stream (about 60muphill from the stream).Theyouthhadnoticedaflockofnoisybirds,andsubsequentlydiscoveredthenest,whilecuttingandburninghisjhumfieldin2001.Accordingtohim,theyhadnestedsuccessfullyin2001.Thecavitywasatabout23m,whiletheheightofthenesttreewasabout30m.Theshapeofthecavitywasoval-elongatedandthecavitywaslocatedonaprimarybranch.Theholewassouth-facing.Thenesthadaflockoffourbirds,whichweremakingfeedingvisits.Onewaspossiblytheadultmale,andtheotherthreewere

Table 2. Food species of Rufous-necked hornbill and Austen’s Brown hornbill in eastern Arunachal Pradesh.

Treespecies Family *Peakfruitingperiod Fruittype&colorofripefruit Observationmethod&season

Polyalthia simiarum (Kari)

Annonaceae May to June&Dec-Feb

(bothseasons)

Lipid-richdrupaceouscarpel,black

Regurgitated seeds below nest tree

Dysoxylum binectariferum (Banderdima) Meliaceae March-April

(breeding)Multi-seededarillatecapsular

fruit,arilblack Nest trees and trail walk

Chisocheton paniculatus(Banderdima) Meliaceae May-June

(breeding)Multi-seededarillatecapsular

fruit, aril orange-white Nest trees and trail walk

Horsfieldiakingii(Ramtamul) Myristicaceae Feb-March

(breeding) Single-seededcapsularfruit Regurgitated seeds below nest tree

Aglaia sp. Meliaceae Feb-April(breeding)

Multi-seededarillatecapsularfruit, orange-red

Regurgitated seeds below nest tree

Beilshmediasp. Lauraceae Oct-Nov (non-breeding) Lipid-richfleshydrupe,black Trail walk, regurgitated seeds

belowfruitandperchtrees

Cryptocaryasp. Lauraceae May-July(breeding) Lipid-richfleshydrupe,black At nest

Canarium resiniferum(Kaladhuna)

Burseraceae Nov-Dec(non-breeding) Lipid-richfleshydrupe,black Trail walk

Cinnamommum cecidodaphne (Gonsorai)

Lauraceae Nov-Dec(non-breeding) Lipid-richfleshydrupe,black Trail walk

Hoveniaacerba(Chetiabola) Rhamnaceae March?

(breeding) Drupe Trail walk

Unidentifiedspecies Meliaceae March(breeding)

Multi-seededarillatecapsularfruit Perchtree

*Platea latifolia Icacinaceae Nov-Dec(non-breeding) Lipid-richfleshydrupe,black —

Ficusmacclellandi Moraceae Availableinbothseasons Fig(syconia),brightyellow Trailwalk(April)

Ficusaltissima Moraceae Availableinbothseasons Fig(syconia),red Trail walk

Ficushookeri Moraceae Availableinbothseasons Fig(syconia),reddish-black Trailwalk(November)

Ficussp.1 Moraceae Not known Fig(syconia) Trail walk

Ficussp.2 Moraceae Not known Fig(syconia) Trail walk

*NotrecordedasfoodspeciesinNamdaphabutfruitcharacteristicsindicateitisahornbillfoodspecies.RecordedinWreathedhornbills’dietinnon-breedingseasoninwesternArunachal.



helpers.ThelocalyouthwhoshowedmethenesthadnotseenAusten’s Brown Hornbills before, though he was familiar with otherhornbill species in thearea.Onasubsequentnestwatchoftwohourson28April2002,Iagainobservedfourbirds,eachtaking turns in feeding2–3 food items, several timesduringavisit.Inasecondvisit,aboutanhourlater,differentindividualsfedthefemale,andchicks8–9times.Thechicks(possiblythree)hadalreadyhatched,astheycouldbeheardcallingfrominside.ThisisthefirstrecentrecordedinstanceandevidenceofAusten’sBrownHornbillbreedinginthewildinIndia.

Thisnesttreewasalsoactivein2003;howeverinthebreedingseasonof2004,thebirdsdidnotnestonthistree,possiblydueto increasedhumanactivityanddisturbance in thevicinityofthenest.OneadditionalnestofthisspecieswaslocatedinMiaoRF(305m)inMay2004,whichwasagainfoundtobeactivein2006, 2007, and in 2008.Despite intensive searcheswithin theHaldibari–Bulbuliaarea,noactivenestcouldbefound.Austen’sBrownHornbill is reported to be amonogamous, territorial,and co-operative breeder. InThailand, its breeding season isfromFebruarytoApril(Poonswadet al. 1987).Fromourlimitedobservations,itappearsthatitsbreedingseasoninnorth-easternIndiacommencesinmid-April,andisoverbyJune–July.

Nest tree species Thenest tree speciesusedby these twohornbill specieswerealllargeemergenttreessuchasTerminalia myriocarpa, Ailanthus grandis and Altingia excelsa.Otherpotentialnesttreespecies(all

Table 3. Structural characteristics of nest sites of two hornbill species in Arunachal Pradesh

Parameters Austen’s Brown HornbillN=1

Rufous-neckedHornbillN=2

Treedensity(perha)(trees≥25cmGBH)

NR 410 ± 56.56

Nest tree height (m) 30 34 ± 6Nest tree GBH (cm) > 400 708.5 ± 27.5

Emergence (m) 20 22.5 ± 7.5

Heightofcavityfromground(m)

23 19 ± 3

Heightoffirstbranch(m) NR 18 ± 8

Girthatcavity(cm) NR NR

Cavitylength(cm) NR NR

Cavitywidth(cm) NR NRDistance to habitation (m) 500 1500 ± 0.0

Distance to road (m) 700 6000 ± 4000

Distance to river (m) 1000 2500 ± 500Altitude (m) 200 1100 ± 300

AmaleRufous-neckedHornbill(about2-yearsold)inNamdaphaNationalPark.

Datta:Rufous-neckedandAusten’sBrownHornbillsPhoto: A

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emergents) in theareaareDipterocarpus macrocarpus (Hollong)and Shorea assamica (Mekai).Tetrameles nudiflora (Bhelu) is themostcommonnestingtree(emergentsoftwoodspecies)usedbyhornbillsinthefoothillforestsinwesternArunachal.However,thespeciesdoesnotseemtooccurineasternArunachal(somewereseeninlowlandforestsinAssam).T. nudiflorawasnotobservedintheMehaoWS(DibangValleydistrict)orinNamdaphaNP,eveninrelativelylowerelevationfoothillforests.InNamdaphaNP,A. excelsa, T. myriocarpa, A. grandis andtwodipterocarpspecies,S. assamica and D. assamicusarethecommonemergentspecies,andmaybemoreimportantnesttreespeciesforhornbills.

In all, four nests of Rufous-neckedHornbill have beenrecorded, twoeachonT. myriocarpa and A. excelsa.Overlap innestinghabitatbetweentheRufous-neckedHornbillandtheotherhornbillspeciesislargelyprecluded,sinceitgenerallyoccursinhigherelevationforests,from800mtoabove1500m,thoughinNamdaphaNP,theyarealsosightedatsimilarelevationsasGreat,Wreathed and Austen’s Brown Hornbills. Great Hornbills are reportedupto1,200mandthoughWreathedHornbillsdooccurupto2,000m,theyaremorecommonatlowerelevationsandareoftenseasonalvisitorsathigherelevationforestsofNamdaphaNP,TaleWS,andothercommunityforestareasinLowerSubansiriandEastKamengdistricts(A.Datta,unpubl. data).

Table3liststheparametervaluesofsomenesttreesfound,ofthetwospecies.

Heightandsizeoftreesaswellascommonnessinthehabitatareimportantfactorsinnesttreeselection(Datta&Rawat2004).StudiesonAsianhornbills,acrossmanysites,haverevealedthatgenerallyhornbillschoselargeemergenttreeswithcavitieshighuponthetreecomparedtorandomlylocatedtrees(Kinnaird&O’Brien2007).Whileinsomeareas,hornbillspecieschooseafewparticularsoftwoodspecies,inothersthemainnesttreespecieswerehardwoods (Thailand and some areas in SEAsia), andPoonswad(1995)contendsthatthisisprobablybecausesuchtreeslastlongerandcanbeusedbynestinghornbillsforalongtime,giventheirdurability,oncecavitiesformonthem.Ontheotherhand,itisalsolikelythatsoftwoodspecieslikeT. nudiflora that roteasily,arelikelytoformcavities.InsouthernIndia,hornbillsdidnotshowapreferenceforanyparticularspecies(Mudappa&Kannan1997).

Proximate structural characteristics (tallness, emergence,softwood, easy cavity formationdue towoodpecker/barbetactivityorbreakageofbranch)of some treespeciesdeterminewhethertheyareusedornot.However,hornbillswillultimatelyselecttreesbasedonavailabilityorcommonnessofaparticularspeciesthatmeetsthestructuralcharacteristics(Datta&Rawat2004).

Myobservationsindicatethathornbillsdonestinloggedanddegradedforest, thoughtheseattemptsareoftenunsuccessful,mainlydue to anthropogenicdisturbances.Hornbillsmaybeabletonestsuccessfullyeveninsuchmarginalhabitats,iffurtherdegradationof,ordisturbanceat,thenestsite(especiallyinthebreeding season) is prevented.Given the limited availabilityof suitable nesting trees and the fact that hornbills nest insuchmarginal habitats, it is necessary towiden the scopeofconservationplans forhornbills to include forestsoutside theexistingprotectedareanetwork,whichformsmorethan70%oftheforestareaofArunachalPradesh(Datta&Rawat2004;Kinnaird&O’Brien2007).

Conservation threatsMost ofArunachal Pradesh is hillywith inaccessible terrainandhaslowhumanpopulationdensities.Thefoothill lowlandhabitat,wheremosthornbills’nestingoccurs, is threatenedbyhabitatlossanddegradationduetologgingandlandclearingforsettlementsandagriculture(Datta&Rawat2004).Loggingalsohasledtothecreationofroadsandgreateraccessibility,whichhasbeenfollowedbycreationofsettlementsandgreaterincidenceofhumanactivitiessuchashuntingandcollectionoffuelwoodand

ThetailfeathersoftheGreatHornbillarehighlyvaluedforuseintraditionalheaddresses by the WanchoineasternArunachal;in1997,asingletailfeather

costRs600/-andwerehardtoobtainastheGreatHornbillappearstobelocallyextinctorveryrareinpartsofTirapdistrict.Thetailfeathersarekeptcarefullywrappedinbananaleaves,Konnuvillage,UpperWanchoarea,November1997.

Heads/beaksofthreespeciesofhornbills(RNH,WH,GH)displayedinhouseholdinaTangsavillage,easternArunachal.

HeadofayoungRufous-neckedHornbillseenwithanApatanihunterin TaleWildlifeSanctuary,LowerSubansiridistrict.


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forestproducts thatcreateadditionaldisturbance(Datta1998).Logging was banned in 1996, though logging has restarted now inseveralforestdivisions.However,althoughloggingdoesresultinreducedabundanceofhornbills,severalstudieshaveshownthathornbills areable topersist in logged forests (Johns1987,1989;Datta1998).

Hunting of hornbills during the breeding season is taboo in manyareas,butiscarriedoutduringthewinterfromNovemberto February (non-breeding season). There is a great demandforhornbillcasques,meat,fatandfeathersalloverArunachal,particularly among certain tribes, and these are either soldorbarteredinexchangeforgoods(Datta1998,2002).Hornbillshavebecomevirtuallyextinct,orveryrare,inmanyareasineasternandcentralArunachal(Datta2002).ApartfromtheRufous-neckedHornbill,whichfrequentsforestsabove800m,allotherspeciesare largely restricted to lowland forests, theextentofwhich isfastdeclining.

Rufous-necked Hornbill:Thisspeciesisamongthetengloballythreatenedhornbills.ItisbelievedtobeextinctinNepalandisalsonearextinctioninVietnam(IUCN2009).Itscurrentglobaldistribution is north-eastern India (primarily inArunachalPradesh), Bhutan,Myanmar, northern andwesternThailand,southernChina, northernLaos, andVietnam. Its presence inCambodiaisunconfirmed.Thespeciesoccursinhillevergreenforestfrom600mto2200m.HuntingistheprimarythreattotheRufous-neckedHornbillinArunachalPradesh.Thisistheonlyhornbillspeciesfoundathigheraltitudes(>1,000–2,000m),andistargetedextensivelybyhuntersinthesurveyareas.InwesternArunachal, it ishuntedbyNishi, Adi and Apatani, and by the Wancho, Tangsa, Miju Mishmi and Lisu ineasternArunachal—andthese tribes havedistinct names for the species (Table 4). In1997, I recorded32Rufous-neckedHornbill headsondisplay(huntedoverseveralyears)inasinglehouseholdinPongchau,a WanchovillageinTirapdistrict.61%ofallhornbillheadsseenin35households,across17villages,wereoftheRufous-neckedHornbill(Datta2002).

Austen’s Brown Hornbill:Itisprobablythemostthreatenedofthehornbillsinnorth-easternIndia,intermsoftotalpopulationinIndia,becauseofanaturallyrestrictedandlocalisedrange.Itshabitatismostlydenseevergreenforestanditisrestrictedtobelow1,000m.Lowlandandfoothillforestsarethemostvulnerabletologging,conversiontoteaestates,settlements,andclearingforagriculture.Therehasbeenextensivehabitatloss/modification(especially inupperAssamandTirapdistrict).Huntingofthisspeciesoccurs, by theTangsa and Wancho, butmuch less than

thatofotherhornbillspeciesbecauseofitssmallersizeandlackof spectacular strikingplumage. In easternArunachal, localknowledgeofAusten’sBrownHornbill issketchy.Whilesomevillagesandtribes,Lisu, Tangsa and some Wancho, were aware of thisspeciesandknewitshabits,insomenearbylocalities,peoplewerenotawareofit.Commonnamesforthesespeciesaregivenby Tangsa, Lisu, Khampti and the Miju Mishmi.ThespeciesismostcommonlysightedinNamdaphaNPinlow-elevationevergreenforestintheDeban–Haldibari–Bulbuliaareaandseenfurtheruptillthe58thmileontheMiao–VijaynagarRoad.ThebestplaceforthesetwohornbillspeciesisNamdaphaNP.

AcknowledgementsSomeofthesesurveyswerecarriedoutasafollow-uptoa4-yearstudyonhornbillsandcontinuedaspartofalong-termmonitoringprogramonhornbills.IthanktheWildlifeConservationSociety—NYforfundingtheearlierworkthroughanRFPgrantandsubsequentlythroughannualin-housegrants.IthankUllasKaranthandtheWCS-Indiaprogram,Bangaloreforvarioussupportandfacilitation.IthanktheArunachalPradeshForestDepartmentforpermissions(especiallyShriK.Namchoom,ex-CCFandP.Ringu,DCFatItanagar)andgratefullyacknowledgethehelpandsupportofnumerousForestDepartmentofficeandfieldstaffatNamdaphaNP,KamlangWS,DeomaliandJairampurForestDivision.IespeciallythankR.Naik,D.N.Singh,A.Gupta-Chowdhury,S.Chandiramani,B.Banerjee,R.K.Deori,D.Ssrra,P.B.Rana,S.Talukdar,O.P.Mall,RHayaliang,andWangoWangsa.Ithankthevillagersinthesurveyareasfortheirhospitalityandsharingtheirknowledgewithme.IamindebtedtoJapangPansa,my guide/friend, for sharing his knowledge and a memorable time in Namdaphaand surveys inother areasof easternArunachalbetween1996and2003.Subsequentlyfrom2004onwards,IthankAkhiNathany,DuchayeYobin andNgwa-akhiYobin for theirwonderful company,assistanceand sharing theirknowledgeofNamdapha. I thankPratapSingh,G.S.RawatandM.D.Madhusudanforinputsandhelp.

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Documents

Observations on Rufous necked Aceros nipalensis and Austen's Brown Hornbills in Arunachal Pradesh: natural history, conservation status and threats