90 Indian Birds Vol. 5 No. 4 (Publ. 15th October 2009) A conservation status survey of hornbills (Bucerotidae) in the Western Ghats, India Divya Mudappa & T. R. Shankar Raman 1 Mudappa, D., & Raman, T. R. S., 2009. A conservation status survey of hornbills (Bucerotidae) in the Western Ghats, India. Indian Birds 5 (4): 90–102. Divya Mudappa & T. R. Shankar Raman, Nature Conservation Foundation, 3076/5, IV Cross, Gokulam Park, Mysore 570002, Karnataka, India. Email: [email protected][ 1 Corresponding author.] Abstract The Western Ghats biodiversity hotspot in India is threatened by habitat loss and fragmentation, which is likely to impact large-bodied, wide-ranging species with specialised requirements such as hornbills. In this survey along the Western Ghats, we surveyed for four hornbill species that occur here: Malabar Pied Hornbill Anthracoceros coronatus, and Indian Grey Hornbill Ocyceros birostris (endemic to South Asia), Malabar Grey Hornbill Ocyceros griseus (endemic to the Western Ghats), and the Great Hornbill Buceros bicornis. We visited 45 localities across five states: Maharashtra, Goa, Karnataka, Kerala, and Tamil Nadu. These included 26 wildlife sanctuaries, 5 national parks, 13 reserved forests, and one plantation landscape. Across sites, we walked 80 transect surveys totalling a length of 286.4 km. In all, 631 individual hornbills (412 detections) were recorded across 35 localities. The Malabar Grey Hornbill was most frequently detected, and widely-distributed, followed by the Great, and Malabar Pied hornbills. The Indian Grey Hornbill, more widespread across India, was seen in only two locations in this survey. Hornbill encounter was up to five times higher in moist, and wet forests as compared to dry forest types. Based on hornbill distribution and protected areas, five important hornbill conservation landscapes were identified in the Western Ghats (Amboli–Goa–Dandeli, Anamalai–Parambikulam–Vazhachal, Nilgiris– Wayanad, Someshwara–Sharavati–Mookambika, Neyyar–Peppara–KMTR, and Periyar) along with key reserved forests (Kottiyoor, NewAmarambalam, Vazhachal, Nelliampathy, Goodarickal, Kulathupuzha– Palode). Hornbill densities were estimated in two of the above landscapes, and are provided as a baseline. We highlight some key considerations for hornbill research and conservation, and future needs. Introduction A large body of research has shown that the threats of habitat loss, and fragmentation severely impact large-bodied, wide-ranging species as well as species that have highly restricted geographic ranges or specialised requirements. Among birds, for instance, this makes wide-ranging species such as hornbills, and restricted-range species (endemics), more significant for conservation attention. The sensitivity of hornbills to hunting and habitat disturbance, and their specialised requirements for diverse old-growth forests for feeding and nesting have been amply demonstrated across Asia (see Poonswad & Kemp 1993; Kinnaird & O’Brien 2007—for recent syntheses), including India (Reddy 1988; Kannan 1994; Kannan & James 1997, 2006; Mudappa & Kannan 1997; Mudappa 2000; Datta 1998, 2001; Datta & Rawat 2003, 2004; Balasubramaniam et al. 2004). Even in the case of the more widespread Indian Grey Hornbill, a species of drier and more open habitats, sensitivity to habitat alteration leading to local extinctions have been reported in studies at the northern extremity of the Western Ghats—Purna/ Ratanmahal, Gujarat (Trivedi & Soni 2006). In central Indian forests, their sensitivity to habitat disturbance due to logging has also been reported (Mehta 1998). Of the 54 species of hornbills known from the world (Kemp 1993), nine occur within India, and four occur in the Western Ghats: the Malabar Pied Hornbill Anthracoceros coronatus, and Indian Grey Hornbill Ocyceros birostris (endemic to the Indian Subcontinent), Malabar Grey Hornbill Ocyceros griseus (endemic to the Western Ghats), and the endangered Great Hornbill Buceros bicornis. Apart from the two smaller Ocyceros spp., all other hornbill spp., are rare and threatened, and have been placed under Schedule I of the Indian Wildlife (Protection) Act, 1972 1 . Past research on hornbills in India has addressed many aspects of their biology such as breeding, nest selection, and diet (Reddy 1988; Kannan 1994; Kannan & James 1997, 2006; Mudappa & Kannan 1997; Mudappa 2000, 2005; Datta 2001; Datta & Rawat 2003, 2004; Balasubramanian et al. 2004). Less information is available on distribution and abundance patterns of hornbills, particularly in the face of large scale landscape transformations and continuing fragmentation and disturbance (Datta 1998; O’Brien et al. 1998; Reddy et al. 1990; Raman & Mudappa 2003). A recent survey by Balasubramanian et al. (2004, 2007) recorded hornbill distribution in a number of sites in Kerala, Tamil Nadu, Karnataka, and Goa in the Western Ghats, as well as in parts of the Eastern Ghats. This survey found the Malabar Grey 1 All hornbills (Family: Bucerotidae) were earlier placed in Schedule I; however, the two smaller Ocyceros have been removed from the listing. In what is possibly an oversight, the Malabar Pied Hornbill Anthracoceros coronatus appears to have been omitted from the listing as currently (15 August 2008) evident on the website of the Ministry of Environment and Forests, Government of India (http://envfor.nic.in/legis/wildlife/wildlife1.html).
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90 Indian Birds Vol. 5 No. 4 (Publ. 15th October 2009)
Ratanmahal,Gujarat (Trivedi&Soni 2006). In central Indianforests,theirsensitivitytohabitatdisturbanceduetologginghasalsobeenreported(Mehta1998).
Ofthe54speciesofhornbillsknownfromtheworld(Kemp1993),nineoccurwithinIndia,andfouroccur in theWesternGhats: the Malabar Pied Hornbill Anthracoceros coronatus, and IndianGreyHornbillOcyceros birostris(endemictotheIndianSubcontinent),MalabarGreyHornbillOcyceros griseus(endemictotheWesternGhats),andtheendangeredGreatHornbillBuceros bicornis.Apart from the two smallerOcyceros spp., all otherhornbill spp., are rare and threatened, andhavebeenplacedunderScheduleIoftheIndianWildlife(Protection)Act,19721. PastresearchonhornbillsinIndiahasaddressedmanyaspectsoftheirbiologysuchasbreeding,nestselection,anddiet(Reddy1988;Kannan1994;Kannan& James1997, 2006;Mudappa&Kannan1997;Mudappa2000,2005;Datta2001;Datta&Rawat2003, 2004; Balasubramanian et al. 2004). Less information isavailableondistributionandabundancepatternsofhornbills,particularlyinthefaceoflargescalelandscapetransformationsand continuing fragmentation anddisturbance (Datta 1998;O’Brienet al.1998;Reddyet al.1990;Raman&Mudappa2003).ArecentsurveybyBalasubramanianet al.(2004,2007)recordedhornbill distribution in a number of sites in Kerala, Tamil Nadu, Karnataka, and Goa in the Western Ghats, as well as in partsoftheEasternGhats.ThissurveyfoundtheMalabarGrey
1 Allhornbills(Family:Bucerotidae)wereearlierplacedinScheduleI;however,the two smaller Ocyceroshavebeenremovedfromthelisting.Inwhatispossiblyanoversight, theMalabarPiedHornbillAnthracoceros coronatus appears tohavebeenomittedfromthelistingascurrently(15August2008)evidentonthewebsiteoftheMinistryofEnvironmentandForests,GovernmentofIndia(http://envfor.nic.in/legis/wildlife/wildlife1.html).
91Indian Birds Vol. 5 No. 4 (Publ. 15th October 2009)
TheWesternGhatsmountain chain, along the country’swestern coast, is recognised as one of the eight ‘hottest hotspots’ of biologicaldiversity in theworld (Myers et al. 2000;Mittermeier et al. 2004),andanecologically important regionwithinIndia.TheWesternGhatshavehistoricallybeenheavilyalteredduetohumanimpactsonnatural landscapes throughurbanisation, agriculture, plantations, hydro-electricprojects,roads, and deforestation (Nair 1991;Menon& Bawa 1997;Williams2003;Kumaret al.2004).Thisisnotsurprisinggiventhatthisregionisoneofthehotspotswiththehighesthumanpopulationdensity(Cincottaet al.2000).Jhaet al.(2000)estimatedthatone-fourth(25.6%)oftheWesternGhats’sforestcoverhadbeenlostoveraperiodof22yearsfrom1973to1995,givinganannualdeforestationrateof1.16%.
Thepresentsurveytargetedtropicalforestareasrestrictedtoelevationsbelow1,500malongtheWesternGhatsfromnorthernMaharashtratoKerala.Weaimedto:(1)assessdistributionofhornbills usingfield surveys and secondary information, (2)identify important hornbill conservationunits based on oursurvey,and(3)estimatepopulationdensityofhornbillsinsomeimportantconservationunitstoserveasabaseline.Thesurveycovered 31protected areas (wildlife sanctuaries andnationalparks)and13reservedforestsalongtheWesternGhats.Alargergoalwas to identify key areas in the regional landscape, forconservation andmanagement of theseflagship species, andtheir habitats.
Study regionTheWesternGhatsisa1,600kmlongchainofhillsrunningalong
thewesterncoastoftheIndianPeninsula,fromnearKanyakumariat8°Natthesouthernend,totheTaptiRiverinthenorthat21°N(Fig.1).TheWesternGhats,distributednarrowlybetween73°and77°E,islessthan100kmwideovermostofitslength,beingwidestin the region of the Anamalai and Nilgiri ranges. Passing through the states of Gujarat, Maharashtra, Goa, Karnataka, Kerala, and TamilNadu,anumberofhillrangeslinkuptoformtheWesternGhats.Goingfromnorthtosouth,theseincludetheSahyadriofMaharashtra and Goa, the hills of Uttara and Dakshina Kannada, Pushpagiri andBrahmagiri, and tall and imposing ranges oftheNilgiri(ameetingpointwiththeEasternGhats),Anamalai,Palni,Cardamom (Elamalai),Varushanad, andAgasthyamalaihills(Nair1991).
TheWesternGhatshasatropicalclimatethatshowspronouncedvariationalongnorth–south,east–west,andaltitudinalgradients.AcomprehensiveaccountofclimateandvegetationintheWesternGhatsisbeyondthescopeofthisreport,andisavailableinotherpublications(Champion&Seth1968;Subramanyam&Nayar1974;Puri et al.1983;Pascal1988).Ingeneral,thevegetationbecomesdrierasoneprogressesfromwesttoeast(rainshadow)acrossthehills.Lowerelevationsontheeasternaspect,receivinglessthan1,200mmannual rainfall, contain tropicaldrydeciduousandthornforest,withtropicalmoistdeciduousforestsinmorewell-wateredareas(Champion&Seth1968).Withincreasingelevation,tropicalwetevergreenrainforestappearsalongthehigherslopesandridges.Thewesternaspectofthehillstendstohavemostlytropicalmoistdeciduousandwetevergreenforesttypesatlowerelevations,givingwaytothelattertypeasoneclimbshigher.ThetropicalwetevergreenforestsoftheWesternGhats,whichareamainfocusofthissurvey,havebeenclassifiedbyPascal(1988)intolow-(mostlybelow<700m),medium-(700–1,400m),andhigh-elevation(>1,400m)types.
Mudappa & Raman: Hornbills in the Western Ghats
MalabarPiedHornbillpair.
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Mudappa & Raman: Hornbills in the Western GhatsMap:A
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evergreenforests),wetforests(primarilytropicalwetevergreenforest),andSahyadriornorthernwetforests(evergreenforeststypical of the northern Sahyadri portion). The survey effortwasdistributedacrossmajorvegetation types as follows:dryforests—12transects,24.52km;moistforests—17transects,30.6km;wet forests—32 transects, 79.4km; and,hilltopevergreenforests—4transects,8.07km.
Identifying key sites for hornbill conservationThe information on number of hornbill species and theirabundance(encounterrates,density)withinsiteswasexaminedwithotherlandscapeandhabitatcharacteristicsthatarelikelytoberelevantfortheconservationoftheselargeandwide-rangingbirds.Weshortlistedlandscapeswithcontiguousprotectedareasofatleast500km²,givinghigherprioritytolargerareasandthoseadjoiningsuitablebufferhabitats (reserved forests,plantationswithshadetreecover).Wealsoexaminedhabitatstatusratingsbasedonanumberofcriteriaassessing the typeand intensityof threats thatwereused ina relatedconservationassessment
State Site TransectsDuration
(min)Length (km)
Maharashtra Amboli RF —
Bhimashankar WS 2 223 4.31
BoriviliNP 1 60 2.04
Kalsubai–HarishchandragadWS 1 45 1.04
Koyna WS 4 383 8.65
LonavlaRF —
Mahabaleswar RF 1 85 1.56
Matheran RF 1 84 2.20
Phansad WS 1 115 3.01
Radhanagari WS 2 315 24.62
Tansa WS 1 68 1.41
Tungareshwar WS 1 70 1.68
TOTAL 15 1448 50.51
Goa Bondla WS 3 204 5.75
Cotigao WS 3 198 5.56
Madei WS 3 263 5.31
MollemWS&NP 6 699 18.07
NetravaliWS 1 56 1.12
TOTAL 16 1420 35.81
Karnataka Anshi NP 2 123 4.15
Bhadra WS 1 60 1.44
Dandeli WS 3 295 7.96
Ganeshgudi–CastleRockRF — + —
Kudremukh NP 1 60 1.34
Makut RF — + —
Mookambika WS 1 69 1.41
SharavatiWS 1 51 1.47
State Site TransectsDuration
(min)Length (km)
Shettihalli WS 1 60 1.34
Someshwara WS 1 60 1.59
Subrahmanya WS 1 64 2.10
TalacauveryWS 1 60 1.61
TOTAL 13 902 24.41
Kerala Aralam WS 1 60 1.34
Chimmony WS 1 60 1.34
GoodrickalRF 1 65 1.22
Malayattur RF 1 61 1.47
Nadugani RF — + —
NelliampathyRF 2 120 2.35
New Amarambalam RF — + —
Parambikulam WS 1 61 1.21
PeechiWS 1 59 1.04
Periyar WS 2 120 2.68
Silent Valley NP 1 60 1.94
Tekkadi RF — + —
VazhachalRF 5 405 8.97
Wayanad WS 1 60 1.41
TOTAL 17 1131 24.96
Tamil Nadu IndiraGandhiWS*survey 4 344 6.93
IndiraGandhiWS*transects 11 c.6000 117.5
Valparaifragmentstransects 4 c.1800 33.2
TOTAL 15 c.7800 157.63
WS—Wildlife Sanctuary,NP—National Park, TR—TigerReserve,RF—ReservedForest,+—visitedbriefly,*—nowknownasAnamalaiTigerReserve.
Materials and MethodsSurvey localities and effortWevisited45localitiesacrossfivestatesalongtheWesternGhats:Maharashtra, Goa, Karnataka, Kerala, and Tamil Nadu. These included26wildlifesanctuaries,fivenationalparks,13reservedforests, andoneplantation landscape.Logistics restricted theamountoftimespentineacharea;althoughwepassedthroughanumberofothersites,itwasnotpossibletogatherfirst-handinformationduetovariouslimitations.
To examinebroadhabitat affiliations,we also categorisedthetransectsintofourmajorhabitattypes:dryforests(drythornanddeciduousforests),moistforests(moistdeciduousandsemi-
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GoaDuringthesurveyacrossfiveprotectedareasinGoa,andnearbyareas,we recorded only twohornbill species:MalabarGreyHornbill(59detections,75individuals),andMalabarPiedHornbill(18detections,25individuals).TheMalabarGreyHornbillwasseen in all five sites,whereas theMalabarPiedHornbillwasrecordedinMollem,Madei,andCotigao.Localreportsindicatethatitalso,occasionally,occursinBondla,andNetravali.
KeralaThree hornbill spp.,MalabarGrey,Malabar Pied, andGreathornbills,wererecordedacross14sitesinKerala(151detections,212 individuals).TheMalabarGreyHornbillwasdetected118times(158individuals)acrossallsitesexceptPeechi,SilentValley,andWayanad (where it almost certainlywasoverlookedduetoshortsurveyperiod).Weobtainedonlyfourdetections(fiveindividuals)ofMalabarPiedHornbill,all fromtheVazhachal-Athirampilly area.GreatHornbillswere detected 29 times(49 individuals), fromChimmony,Goodrickal,Nelliampathy,Parambikulam,Periyar,Thekkadi, andVazhachal.The IndianGreyHornbillwasnotrecorded,althoughtherewerereportsofitsoccurrenceneartheTrichurandChalakudifoothills.
Tamil NaduInTamilNadu,ourfocuswasonestimationofhornbillpopulationdensityinandaroundtheAnamalaiTigerReserve(formerlyIndiraGandhiWildlife Sanctuary).During the survey,detectionsontransectsandothersupplementaryobservationresultedinaround500detectionsofMalabarGreyHornbillandover100detectionsofGreatHornbills numbering over 750 and 250 individuals,
Population density estimationBesidesoccurrence,andencounter ratesof species,populationestimationfromlinetransectsurveysisanimportantaspect inidentifyingkey areas for conservationofhornbills, especiallyfor the larger, threatened species.Among the identifiedareas,givenconstraintsofsurveyeffortandlogistics,wewereabletocarryoutlinetransectdensityestimationacrosstwolandscapes:Dandeli–Goa,andAnamalai–Parambikulam.
Fromhornbilldetectionsobtainedduring the line transectsurveyswe estimated population densities using distancesamplingtechniquesasimplementedintheDISTANCEcomputerprogram(version5.0,Bucklandet al.2003;Thomaset al.2005).Allhornbillsdetectedbysight,orcall,inthefieldwerecategorisedintothefollowingperpendiculardistance(fromthetransectline)intervalsinmetres:0–5,5–10,10–20,20–30,30–50,50–75,75–100,>100,withamaximumdetectiondistance(truncationpoint)of150m.Distanceswereestimatedvisuallytomostsightingsorcalls,bypace-lengthinafewcases,ormeasuredwitharangefinderwheneverpossible.Wetookeachdetection(=cluster)torepresentanindividual,pair,orflockfoundinrelativelycloseproximityandapparentlymovingorforagingtogether,andestimatedflockorclusterdensity.Sinceflockscouldnotbecountedinmanycasesforvisualdetections(andallauraldetections),weusedestimatedaverageflock(cluster)sizeanditsSEfromdatawithinandoutsidetransectswherecompletecountsof individualswereobtained.Wemultipliedtheaverageflocksize(F)bytheaverageclusterdensity (C) toobtain individualhornbilldensity (D).Standarderrorofindividualdensity(seD)wascalculatedusingstandarderrorofclusterdensity(seC)andstandarderrorofaverageclustersize(seF)usingGoodman’s(1960) formula: (seD)²=C²(seF)²+F²(seC)²–(seC)²(seF)².Weevaluateddifferentmodelsofdetectionprobability(half-normal,uniform,andhazard-rate)withcosineadjustmenttermsandusedstandardmodelselectionproceduresinDISTANCEtoselectthebestmodelforestimatingdensity.
Species-wise summariesGreat HornbillThisspecieswasrecordedin13ofthe45surveysites,chieflyinorincloseproximitytowetevergreenforestsatelevationsfrom50mto1500masl.TherecordsrangefromsouthernMaharashtra(Radhanagari andAmboli) to the southern-most sites in theWesternGhats.RelativelyhighernumberswereencounteredinRadhanagari,Anamalaihills(Anamalai,andParambikulamTigerReservesand,VazhachalReservedForests),andPeriyarduringthesurvey.
Malabar Grey HornbillThis endemic species is clearly themostwidely distributed(recordedin33of45localities)andrelativelycommonhornbillin theWesternGhats,distributedover a rangeof forest typesfrommoistdeciduous, riverine, and semi-evergreen forests totropicalwetevergreenforests.Ourrecordsofthisspeciesextendfromaround50melevationto1500melevation,fromPhansadinMaharashtra to the southernmost sites in the Western Ghats.
Indian Grey HornbillThis species,more typical andwidelydistributed across theplateauxandplainsof India, than in theWesternGhats,wasnotedonlyinafewperipherallocalities,orthefoothills,duringthissurvey.ThisincludeddirectrecordsonlyfromBoriviliandDandeli,besidesreceivedreportsofitsoccurrencearoundTrichurandChalakudiinKerala,andanearlierrecordfromPanchgani,Maharashtra(Gole1998).Despitethefewrecordsobtainedinthissurvey,wewouldliketoobservethatthisspeciesisclearlystillrelativelycommonandwidelydistributedacrossIndia,eveninurbancentres(e.g.,NewDelhi,Nagpur,andMysore,tonameafew).However,beingaspeciesendemictoSouthAsiaandoneof the large-bodied species, itmerits continuing conservationattention (R. Sankaran,verbally). Evenduring this survey,weobtainedreportsofhunting,andpoaching,ofnestsofhornbillsin the Western Ghats.
Habitat affiliations of hornbillsHornbillencounter rateswerecalculated fromtransectdata invegetationtypesbroadlycategorisedasdryforests(tropicaldrythornanddrydeciduous),moist forests (chiefly tropicalmoistdeciduousandriverine),andwetforests(tropicalsemi-evergreenandwetevergreen).NohornbillsweredetectedinthefoursitesinthenorthernwetevergreenforestsofMaharashtraandhencethesesiteswereexcludedfromanalysis.Theoverallencounterrateofhornbillsvaried significantlybyhabitat type (Kruskal-WallisANOVAχ²=12.4,df=2,P=0.002).Theencounterratewasaroundfivetimeshigherinmoistforests(mean=2.65hornbills/km,±0.51SE),andwetforests(2.36±0.38),ascomparedtodryforests (0.52 ±0.22). The encounter rates of the four hornbillspeciesinthesethreebroadvegetationtypesindicatestheirmainhabitataffinities(Fig.2).ItisclearthattheIndianGreyHornbillisrestrictedtodryforests,althoughvariationinencounterrateswerenotstatisticallysignificantduetothefewlocationsinwhichthespecieswasseenontransects(Kruskal-Wallisχ²=4.1,df=2,P =0.13).TheMalabarGreyHornbillismorewidelydistributed,andshowedsignificantdifferencesinencounteramonghabitattypes(χ² =13.2,df=2,P=0.001),occurringchieflyinmoistforesttypesandsomedrydeciduousareasadjoiningmoistforesttracts.Thetwolargerhornbillsarerestrictedtomoist/wetforests.TheMalabarPiedwasmorefrequentinmoistdeciduousandriverineareas(χ² =10.2,df=2,P=0.006).TheGreatHornbillwasaspecieslargelyofwetevergreenzone,spillingoverintosomeadjoiningmoistforesttypes,butstatisticalsignificancecouldnotbeestablishedduetoitsrarityandlowdetectionsontransects(χ²=2.0,df=2,P=0.37).
Identifying important hornbill conservation landscapesCompilingtheoccurrencedatafromoursurveyandtheworkofBalasubramanian et al.(2004,2007)presentsapictureofhornbilloccurrenceinrelationtoaltitudeandareaofcontiguoushabitatwithinprotectedareas(PA)wherethehornbillspeciesoccurred(Fig.3).AsseenfromFig.3,thetwosmallerOcyceros hornbills are seenacrossawiderrangeofsitesintermsofcontiguousPAsandaltitudesthanthelargerspecies.Inparticular,theMalabarPiedHornbillappearstohavethenarrowestaltitudinaldistributionin theWesternGhats coupledwith an occurrence primarilyinPAsat least larger than20km². Itmustbenoted,however,that this analysis excludesareasof forest thatmayadjoinPAsand currently lack the same level ofprotection (e.g., reservedforests,plantations).Theeffectiveareaofcontiguousforestthatdeterminestheoccurrenceofthesehornbillspecies(especiallythelargerspecies)isthuslikelytobehigherthanillustratedhere.Fig. 3.Distributionofrangeofsitessurveyedandindividualhornbillspeciesin
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Based on the occurrence of the four hornbill species,encounterrates/densitiesfromthesitesforwhichtheseindicesof abundanceare available, and the configurationand sizeofcontiguousprotectedareasalongtheWesternGhats,aprioritylistofconservationunitsareidentified.Themainsitesandsomekeyaspectsregardingeachare listedbelow(inroughorderofpriority):
Amboli–Goa–Dandeli: This is akey regionbeingperhapsthemost importantregionfor theconservationof theMalabarPiedHornbill as evidenced from the preponderance of therecordsofthisspeciesbeingfromthisregionandtherelativelyhighencounterratesanddensity.Besidesthreecrucialwildlifesanctuaries(Mollem,Madei,andDandeli),asignificantproportionofthepopulationisfoundoutsidedesignatedprotectedareasinreserved forests suchas atAmboli,Ganeshgudi,Dandeli, andaroundMollem–Madei.All fourspeciesofhornbillsare foundin theAmboli–Goa–Dandeli region.Adetailed surveyof thereservedforestsandtheirfragmentationandconservationstatusisrequiredforAmboliandaroundDandeli,forconsiderationofpossibleinclusionwithprotectedareas.
Anamalai–Parambikulam–Vazhachal: Again, a region with all fourspeciesofhornbills,thisareaappearssignificantparticularlyintermsofconservationoftheGreatHornbill.PopulationdensitiesestimatedinandaroundAnamalaiTigerReserveprovideabaselineforthis,andtheMalabarGreyHornbill(seenextsection).Whilethelargeareaofforestandabundanceofthesetwospeciesindicatethattheirpopulationsherearerelativelysecure,thereisconcernoverthestatusoftheMalabarPiedHornbillthatisthreatenedbytheproposedAthirapillydam,andlackofprotectedareastatusforreservedforestswhereitoccurs(e.g.,Vazhachal,Nelliampathy).
Nilgiris–Wayanad:Thisisoneoftheimportantconservationareas of the Western Ghats although fragmented due to dams, roads, agriculture, and timberandmonocultureplantations. Itgainsimportanceduetothelargeareasofdryandwetforests,andtheoccurrenceofallfourspeciesofhornbills.Quantitativeestimatesofhornbillencounter/abundanceare,however,lacking.ThepatchyoccurrenceofMalabarPiedHornbillsontheeastern(Coimbatoreforestdivision)andwestern/northern(Wayanad–
Someshwara–Sharavati–mookambika: In Karnataka, this area appearstobeanimportantcomplexforconservationofhornbills,including theMalabarPiedHornbill, after theAnshi–Dandeliregion.Onlylimitedtimecouldbedevotedtothisregionduringthepresentsurvey.However,earlier reports (Balasubramanian2004)andsightrecordsofflocks(upto32,H.N.Kumara&SushmaRao, in litt.)indicateitspotential.
Neyyar–Peppara–Kalakad–mundanthurai Tiger Reserve: A large,contiguoustractofover400km²oftropicalwetevergreenforest across the twowildlife sanctuaries inKerala and theKalakad-MundanthuraiTigerReservemake this an importantconservation area.Malabar Grey, andGreat hornbills arewidespreadintheevergreenforests,andBalasubramanian(2004)hasrecordedMalabarPiedHornbillatNeyyarWildlifeSanctuaryandTenmalareservedforests.Wedidnotsurveytheseareas.
Periyar:Thetractof777km²underthePeriyarTigerReservehas extensivewet evergreen,moist deciduous, and riverinehabitats. While only Malabar Grey, and Great hornbills were
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recorded here during the present survey, theMalabar PiedHornbill has been recorded here in other surveys (PeriyarFoundation,http://www.periyarfoundation.org/pdf/birds.pdf,accessed16April2009).
Population density estimation in two important hornbill conservation landscapesDandeli—GoaAllfourhornbillspeciesoccurredintheDandeli–Goalandscape.WhiletheIndianGreyHornbillwasonlyseennearDandelitown,theotherthreespecieswereseeninbothGoaandKarnataka.Thewidersurveyalsorevealedtheimportanceofthislandscapeforthe Malabar Pied Hornbill. Two-thirds of the 131 Malabar Pied HornbillsrecordedduringtheentiresurveywereseenacrosstheDandeli–GoalandscapeinKarnataka,Goa,andadjoiningareasofMaharashtra(Amboli).Dandeliwasparticularlyimportantas
largenumbers(c.80birds)wereseenusingtheforestsinthearea,androostinginlargeflocksofupto30individualsalongtheKaliRiver inDandeli,andGaneshgudi.TransectdataalsorevealedthatthehighestencounterratesofthisspecieswereinMollemNationalParkandWildlifeSanctuary(range=0.13/kmto1.61/kmacrosssixtransects),withhighencounterratesinMadeiWidlifeSanctuary,Goa (0/km to 0.84/kmacross three transects), andDandeliWildlifeSanctuary,Karnataka(0/kmto0.6/kmacrossthreetransects).
We were able to obtain initial density estimates of Malabar Grey andMalabarPiedHornbillsfromthetransectdatainthisregion(Fig.4).Weobtained56detectionsofMalabarGreyHornbillsandestimatedadensityof9.4individualsperkm²(95%confidenceinterval:6.1–14.4individuals/km²).Weobtained11detectionsofMalabarPiedHornbillsandestimatedadensityof1.3individualsperkm²(95%CI:0.5–3.0individuals/km²).Itwouldbeworthwhileestablishingasystemoftransectsformonitoring.
A large number of Malabar Pied Hornbills were also seen outsidetheexistingprotectedareasinreservedforestsandsomedisturbedareasaroundDandeli.ThereappeartobeanumberofroostsitesalongtheKaliRiverinDandeliandGaneshgudi(andpossiblyinotherareas).Duringthreeeveningsatdifferentroosts,wecounted30individualsatoneroostsite(Kalimainbridge,14October2005),21atanother(Kalioldbridge,17October2005),and 24 inGaneshgudi.More recently, an intensive study ontheMalabarPiedHornbillhasbeen completed from this area(Vijayakumar2007).
98 Indian Birds Vol. 5 No. 4 (Publ. 15th October 2009)
Anamalai—ParambikulamIntheAnamalai–Parambikulamregion,hornbilldensitieswereestimated from line transects distributed across three broadstrata:a. Wildlife sanctuaries:Anamalai andParambikulamTiger
MalabarGreyHornbilland69detectionsoftheGreatHornbilloverall.Detection functionswere estimated strata-wise for theMalabarGreyHornbill;however,duetofewerdetectionsofGreatHornbill,weusedaglobaldetection functionacross strata forestimationof this species.Detailsof samplingandparametersareprovidedinTable2.
The estimated mean density of Malabar Grey Hornbills in reservedforestswas67.4individuals/km²(Vazhachal–Sholayar,andMalayattur)witha95%confidenceinterval(CI)of40.4–94.4individuals/km².Thisappearedtobesignificantlyhigherthan95%CIofdensitiesinthewildlifesanctuaries(23.9–33.1individuals/km²)or rainforest fragments (18.6–33.4 individuals/km²)—thelattertwostratathusappearingnottodiffersignificantlyfromeachother(Fig.5).Thiswaspartlybecausethetransectsiteswithinthesanctuariesincludedsomehigheraltitudeareaswherehornbillswerescarceorabsent(seebelow).GreatHornbillsdidnotshowsubstantialvariationacross the threestrata (Fig.5)withbroadoverlapinthe95%CIamongsanctuary(1.5–4.4individuals/km²),reservedforest(0–4.0individuals/km²),andfragments(0.6–4.5individuals/km²).
Acloserlookatdensityestimatesfromthemoreintensively-sampledsiteswithintheAnamalaiTigerReserveandrainforestfragmentsontheValparaiPlateauindicatedpatternsofvariationwithin strata (Fig. 6).Within the sanctuary, themeandensityof Malabar Grey Hornbill was higher in three sites at middle elevations(700–1,000m):AnaigundiShola(42.7individuals/km²),KarianShola(48.7individuals/km²),andVaragaliar–Manamboli–Sheikalmudi complex (40.8 individuals/km²).MalabarGreyHornbillswerescarceorabsent(<3individuals/km²)atthetwoothersitesathigherelevations(>1,300m,Fig.6).TheMalabarGreyHornbilldensitieswerebroadlysimilaracrosstheValparaiPlateau fragments (21.5–33.5 individuals/km²).Although theaveragedensities in fragment sites tended tobe lower than inthemid-elevationsiteswithinthesanctuary,the95%CIshowed
An important location forGreatHornbills isa roost site intheValparaiPlateau,adjoiningforestsoftheManambolirangeofAnamalaiTigerReserve,intheAnaliestate(TataCoffeeLtd)and Senthil estate (private ownership).WhileAnali estate ispredominantlyundershade-coffeeandEucalyptusfuelplantations,Senthilestatehasseenrecentconversionfromrubberandcoffeetoteaplantations,thelattercharacterisedbylittleshade.Upto60GreatHornbillshavebeenobservedtousethisroostsiteeveryyearduringthenon-breedingseason.Asthesitepartlyoverlapsprivateteaandcoffeeestates,itrequirestheinvolvementoftheseprivatelandownersintheprotectionofroostingtrees,reductionofdisturbances,andconservationofthisimportantroostsite.
Shortcomings of surveyThesurveyperiodhadtobeextendedduetovariousdifficultiesoflogisticsincludingdelayedpermits,travel,andunpredictableweatherpatterns.Afewofthesitescouldnotbesurveyeddueto these constraints and aswe ran short of time and funds.The surveywas too rapid togivea suitableunderstandingofthe current trends indistributionwithin each of the sites orof seasonalvariationandpatternswithin sites.Among states,TamilNaduwaspoorlycoveredandrequiresmorefieldsurveyinthefuture.Althoughsomelocalknowledgeisavailable,ofthedistributionofmanyspecies,thelackofpublishedinformationandthepreponderanceofgreyliteraturemadeitdifficult,inmanycases,toreliablycollatepastdistributioninformationaswehadexpectedtodo.Wewereabletoestablishpopulationbaselinesonly in tworegionsand for threehornbill species.ThesurveysitesdidnotadequatelyrepresentthedistributionoftheIndianGreyHornbill,whichismoreofaspeciesofthedrierzoneandeasternaspectoftheGhats.
Key findings and recommendations for future effortsThe results of theoccurrence anddistributionpatternsof thefourhornbillspeciesinthissurveyarebroadlyconcordantwithearlier reports (Ali&Ripley 1983) and amore recent survey(Balasubramaniam et al.2004,2007).However,therehasbeenlittlesystematiceffortatestimatingabundanceorpopulationdensitiesofhornbills inearlierwork,and thepresent surveypresentsabaseline,across localities,ofencounterratesaswellasdensityestimatesfromselectareasofimportance.
TheimportanceofmoistforestsfortheMalabarGreyHornbillandthelargerhornbillsalsostandsout.Inaddition,theMalabarPiedHornbillappears toprefer lowerelevationriverineareas,includingmanysitesoutsidedesignatedPAs—habitatspronetoarangeofthreatssuchasencroachments,agriculture,monoculturetimberplantations,hydro-electricandirrigationprojects,tourismandurbandevelopment(e.g.,Vazhachal–AthirapillypopulationalongtheChalakudyRiverthreatenedbytheproposedAthirapillydam).ItisalsonotedtobeanapparentlyirruptiveordispersivemigrantoverawidelandscapeinGoa(Lainer2004).Althoughdistributedmorewidely across localities in central India intoOrissa, and in Sri Lanka, theMalabarPiedHornbill appearsto be currentlypatchilydistributed along theWesternGhatswith reports indicatingdecliningpopulationsparticularly inthesouthernWesternGhatsandKerala (Sugathan&Varghese1996;Sashikumaret al.2005;Nameer&Praveen2006;Praveen&Nameer2009).
Mudappa & Raman: Hornbills in the Western Ghats
Malabar Grey Hornbill female feeding on Vitex altissima.
Phot
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99Indian Birds Vol. 5 No. 4 (Publ. 15th October 2009)
Looking ahead, it is essential to establish baselines through populationestimation,discoveryandmonitoringofnestandroostsites,especiallyinthesitesandlandscapesidentifiedascriticalforhornbill conservationby this survey. In someof the sites,sizablehornbillpopulationsalsooccurinreservedforestsoutsidedesignatedprotectedareas.Theserequireparticularattentionasthesearealsosubjecttogreaterpressuresofhuntingandresourceextractions.Thelargerhornbills,particularlytheGreatHornbill,areknowntobenomadicduringthenon-breedingseason.Duringtheseforays,theyseemtotrackfruitingtreesinhabitatsthattheydonotusuallyresideinandthereforecanbeseenindrydeciduoustractsadjoiningevergreenforests.Therefore,itbecomesnecessaryfortheprotectionandconservationofareasmuchlargerthantheir“preferred”orevennestinghabitats.
Currently10%ofthelandareaoftheWesternGhatsreceivessome levelofprotectionwithin43wildlife sanctuaries and13nationalparks(Rodgerset al.2002;Kumaret al.2004).Substantialareasof forest andnaturalvegetationalso lieoutside existingprotected areas as reserved forests, protected forests, privateforests,grasslands,andwetlands.Considering justthetropicalwetevergreenforestsoftheWesternGhats,arecentassessmentreportsthatonlyone-fourthofthetotalarea(15,057km²)ofthisforesttypeisrelativelyun-fragmented,with74%lyingoutsideprotected areas (CEPF 2007). Information of thedistributionandoccurrenceof speciesobtainedover these landscapes canbeused todesign appropriate conservation strategies. In thelandscape adjoining forest areas in theWesternGhats, largetractsofplantationsaredistributed (over4,500km²of teaandcoffeeplantationsalone),whicharealsooftenimportanthabitatsforwildlife,orareasthroughwhichmanywildlifespeciesmove(Raman&Mudappa2003;Kumaret al.2004;Raman2006;Baliet al. 2007).Inrecenttimes,therehasbeenincreasinginterestworldwideintheconservationvalueofcountrysidelandscapeswithinandaroundexistingconservationreserves.Thereisaneedtopromotehornbillconservationandtheuseofnativeshadetreesamongplantationowners,possiblylinkingwithconservationincentive/certificationschemes.
Line transects appear tobe auseful and easily applicablemethodformonitoringhornbillpopulations(Raman&Mudappa2003;Gale&Thongaree2006).Besidesmonitoringbybiologists—trainedamateurs,volunteers,andforestdepartmentstaffneedtobeinvolvedinhornbillmonitoringassuccessfullydemonstratedinKerala(Praveen&Nameer2009).Thereisaneedtodevelopamanagementandactionplanformonitoring,protection,andconservation of critical hornbill populations. This has to bedevelopedbyacommitteeconsistingoflocalforestdepartment,NGOs,localpeople,andafield/conservationbiologistactingasafacilitator.Atanumberoflocationswefoundlowawarenessofhornbillspeciesoccurrenceorabundance,evenamongforeststaffinprotectedareas.Conservationeducationandawarenessthusneedtogohand-in-handwithallprotectionandconservationefforts.
AcknowledgementsWe shall remain indebted toDr Ravi Sankaran,who inspired andencouragedustotakeupthissurvey.Thesurveywasfinanciallysupportedby the Rufford Small Grants Foundation, UK. We are also extremely gratefultothestateforestdepartmentsofMaharashtra,Goa,Karnataka,Kerala,andTamilNadu,manyofficersandfieldstaff, forpermitsandsupportforthesurvey.SpecialthankstoHariSridharforsharingdataon hornbills from the Anamalai Hills for density estimation, and for commentson themanuscript.A largenumberofpeople, institutions,andlocalNGOs—toomanytoindividuallyacknowledgehere—helpedusduringthevariousstagesofthesurveybothinthefieldaswellasatthe base. We are grateful to all of them.
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