Breeding Biology of the Malabar Grey Hornbill (Ocyceros Griseus) in Southern Western Ghats, India

10 Pages·2000·6.9 MB·

by  Divya Mudappa

BREEDING BIOLOGY OF THE MALABAR GREY HORNBILL
{OCYCEROS GRISEUS) IN SOUTHERN WESTERN GHATS, INDIA.'
DivyaMudappa2
(With one text-figure)
Key words: hornbill, tropical rainforest, frugivory, seed dispersal, cavity-
nesting, breeding biology
The Malabar grey hornbill (Ocyceros griseus) is a frugivore, endemic to the tropical
rainforests and moist deciduous forests ofthe Western Ghats hill ranges, India. I studied
itsbreedingbiology intheAnamalaihills(IndiraGandhi WildlifeSanctuary),Tamil Nadu
state, by monitoring 10 nests and their middens, and conducting intensive observations at
a focal nest. The nesting period lasted an average of86 days (N=4), and observations at
thefocalnestrevealedthepre-andpost-hatchingphasestobe40and46days,respectively.
At the end ofthe nesting period, the females and the young simultaneously broke out of
thenests. A total of2397 itemsoffoodweredelivered bythe male hornbill tothe inmates
ofthe focal nest. They included 6 species oflipid-rich and 8 species ofsugar-rich fruits,
and at least 14 kinds ofanimal matter. Lipid-rich fruits formed a major component (c.
37%) ofthedietduringnesting. Ficusfruitsformed 26%, and animal matter 13.8%ofthe
diet ofthe incarcerated hornbills. The frequency ofsugar- and lipid-rich fruits delivered
per hour of observation was significantly greater in the pre-hatching phase. While the
frequency ofanimal food delivered was higher in the post-hatching phase. Although the
Malabar grey hornbill used a wide range offood resources, it was observed that a few
species ofrare, tropical trees producing lipid-rich fruitsduringthe nesting period, play an
important role in the maintenance ofthe species.
Introduction Basalingappa 1995). Hornbills are secondary
cavity-nesters,andtheforest-dwellingspeciesare
Hornbills (Aves Bucerotidae and predominantlyfmgivorous.Theirbreedingcycles
:
Bucorvidae) are a group of large, forest and are synchronous with food productivity of the
savannabirdsrestrictedtotheOldWorldtropics. forest (i.e., fruiting phenology; Kannan 1994),
There are 54 species of hornbills in the world buttheyarealsodependentonkeystoneresources
(Kemp 1988, 1995),nineofwhichoccurinIndia likeFicus fortheirsurvival intimes oflow food
(Ali and Ripley 1987). Only in the last two availability. They exhibit wide-ranging
decades, a few studies have provided valuable movements to meet their specialized food
insights into the ecology ofthese unique cavity- requirements (Poonswad 1994). Functionally,
nesting birds (Hussain 1984, Kannan 1994, theyhavebeen describedaskeystone mutualists
Kemp 1976, 1978, 1988, Kinnaird 1993, (Gilbert 1980) as they play an important role in
Leighton 1982, Poonswad 1995, Poonswad and the dispersalofmanyrare rainforesttree species
Tsuji 1989, 1994, Reddy etal. 1990, Reddy and (Kinnaird 1998, Whitney et al. 1998).
The present study aimed to determine the
'AcceptedJune, 1998 nesting habitat requirements and breeding
:CentreforEcologicalResearchandConservation
3076/5IVCross,GokulamPark biology of the Malabar grey hornbill, endemic
Mysore570002,Karnataka,India. to the Western Ghats. The formeraspect is dealt
JOURNAL, BOMBAYNATURAL HISTORYSOCIETY, 97(1), APR. 2000 15
BREEDINGBIOLOGYOFTHEMALABARGREYHORNBILL
with elsewhere (Mudappa and Kannan 1997). occuring only in the heavy rainfall tracts ofthe
This paper describes in detail: 1) nesting Western Ghats hill ranges. Most of the
activities and behaviour ofthe male and female information on the Malabar grey hornbill and
hornbill, 2) duration of nesting period and other Indian hornbills is anecdotal-with notes
distinct phases of the nesting cycle, and 3) on natural history. Early papers dealing with
qualitative and quantitative data on the food nidificationoftheMalabarandthecommongrey
deliveredby the male to the incarcerated female hornbills (Ocyceros birostris) are those of
andyoung, inrelationtothephasesofthenesting Bingham (1879), Hall (1918), Lowther (1942),
period. The results are compared with other and Abdulali (1942). More comprehensive
hornbill species, their reproduction and survival informationontheirecology and behaviourwas
strategies,andtheimplicationsfortheconservation provided by Ali and Ripley (1970, 1987) and
ofthis rainforest endemic are discussed. Kemp (1978).
The Malabar grey hornbill is sexually
Study Area dimorphic: the male has a large, bright orange
bill andgoldenbrown iris, while the female has
The study was undertaken between arelativelysmallandpale-colouredbillanddark
December 1993 and May 1994 at the Indira brown iris. The species is monogamous, the
Gandhi Wildlife Sanctuary (10°13' - 10°33' N nesting pair usually exhibiting high nest-site
and 76°49' - 77°21' E, anarea of968 km2) inthe fidelity, occupying the same nest-cavities every
Anamalai Hills ofthe southern Western Ghats, year(Kemp 1978,AliandRipley 1987,Mudappa
in Tamil Nadu state, India. A one-month long and Kannan 1997). The Malabar grey hornbill
preliminary study was carried out in the area in exhibits biparental care like most other
May-June 1993, when 15 nests were discovered monogamousbirdswithaltricialyoung(Clutton-
and seeds from the middens were collected and Brock 1991). While the incubating female is
identifiedforfuturereference.Thenestsselected incarcerated, the male provisions her and the
for intensive observation and monitoring were other inmates ofthe nest.
in the 5.1 km2 wet evergreen' forest patch of
Karian Shola National Park. This forest, Methods
classifiedas a SouthernTropicalWetEvergreen
Forest (Champion and Seth 1968), receives an Active nests ofthe Malabar grey hornbill
annualrainfallofabout 1500 mm. The terrain is were located with the help of a local field
m
hilly, and the altitude ranges from 350 to assistant, by following the parent birds, and by
m
2400 above msl in the Sanctuary, which checking for signs ofprevious nesting, such as
extends into Parambikulam Wildlife Sanctuary seeds andfaecalremains(midden) atthebase of
and Eravikulam National Park in the adjacent the nest trees. Fifteen nests were located during
Kerala state. The forestis contiguouswithmoist the preliminary study in May 1993. Seeds
deciduous, teak (Tectona grandis) and bamboo collected from the midden were catalogued and
forests in the surrounding areas. used for reference during the study. Twelve
additional nests were discovered during the
Study Species initialhalfofthestudy(December 1993 toMarch
1994). Ten nests were chosen for monitoring
Ofthe 9 species ofhornbills in India, the during the nesting period (the period of
Malabargrey hornbill (Ocycerosgriseus), is the incarceration of the female and the young) in
smallest. ItisendemictotheIndiansubcontinent. Karian Shola National Park. Ofthese, one was
16 JOURNAL, BOMBAYNATURAL HISTORYSOCIETY, 97(1), APR. 2000
BREEDINGBIOLOGYOFTHEMALABARGREYHORNBILL
selected on the basis of logistics for intensive belowthenest-treewasclearedofalldebrisafter
observation. each visit. Small seeds and animal matter in the
Intensiveobservationofafocalnest:The faecal remains could not be quantified. The
focal nest was observed from the last week of presenceofMalabargreyhornbill feathers inthe
January 1994 to May 1994, for approximately midden was taken to indicate moulting.
six-hour intervals on every alternate day (more Similarly, the presence of egg-shell in the
or less uniformly) throughout the three-month midden, orthecharacteristicbeggingcallsofthe
nestingperiod. Observationsweremadebetween young,wereevidenceofhatchingorthepresence
0700 h and 1300 h. The forenoon was chosen ofchick(s) in the nest.
for nest observation, while the rest of the day Statisticalanalyses:Thefrequencyoffood
was used to visit the other nine nests. items delivered during the nesting period was
I observed the nest to gather information calculated. Differences between the food (type
on the quantity and quality offood deliveredby andquantity)consumedbetweenthetwodistinct
the male to the incarcerated inmates. The food phases (pre- and post-hatching) of the nesting
wasbroadly classified asplantand animal food. period were tested for statistical significance
Theplantfoodwasfurthercategorisedas: a)figs, using Mann-Whitney U test (Seigel and
b) sugar-rich non-fig, and c) lipid-rich fruits, Castellan 1988), using SPSS/PC+ computer
based on McKey (1975) and Snow (1981). software (Norusis 1990). The difference in the
Observations were made from a ground hide occurrence of seeds (frequency) in the midden
about 18mfromthebaseofthefocalnestthrough was tested for significance, using the non-
a7x50binocularsora20x50spottingscope. For parametric Mann-WhitneyU Test similarto the
each visit by the male hornbill to the nest, I analysis ofdirect feeding observation.
recorded the number and type of food items
delivered, thedurationofthevisit(tothenearest Results
5 seconds), and the totalnumberofvisits during
each sampling/observation session. Ad libitum Characteristics and occupation of focal
observations on other activities like nest-cavity nest: The focal nest cavity was located at about
m
sealing, cleaning, excretion, begging by the 14 on an Artocarpus lakoocha (Moraceae)
inmates, and the behaviour of the male during tree. The diameter at breast height (1.2 m) of
the time offood delivery were recorded. At the the focal nest tree was 56 cm, the height 25 m,
end ofeach session, the seeds and other faecal and the estimated diameter at nest height was
remainsinthemiddenwereexamined,identified, 50cm.Thecavityentrancewascircularinshape,
classified, and counted. and oriented towards northwest. My field
Nest midden monitoring: Ten nests assistant observedabirdentering the nestcavity
(including the focal nest) were visited regularly inthe firstweek ofFebruary. This wasprobably
to note the status of nesting, quantify the an instance of nest preparation, cleaning, and
regurgitated orexcreted seeds ofthe fruits eaten widening ofthe nest entrance.
by the inmates, and to identify the other debris After this, there was regular movement of
in the midden. Ofthe food items consumed by the breeding pair inthe vicinity ofthe nest-tree.
thenest-cavityinmates,onlynon-digestibleparts On February 17, the female hornbill was seen
such as seeds of fruits, elytra of insects, and enteringthenest-cavity.Thecavityentrancewas
reptile scales occur in the midden. All thenhalf-sealed.Themaleandthefemalevisited
distinguishable midden remains were collected, the nest (8 times in 6 hrs). During these visits,
identified, counted, and recorded. The midden theyappearedtobeenlargingthecavityentrance.
JOURNAL BOMBAYNATURAL HISTORYSOCIETY, 97(1), APR. 2000 17
,
. ,
BREEDINGBIOLOGYOFTHEMALABARGREYHORNBILL
The female was in the nest on February 18, and Table
1
wasseensealingthecavityentrance,leavingonly DATESOFINCARCERATIONANDFLEDGING
INTHESTUDYNESTS
a slit, through which the male fed the inmates
during the nesting period. Nestnumber Dateof Fledgingdate
The male was never observed to be incarceration
involvedinnestsealing,repair, ordeliveringany 1. 17February 16May
kindofsealingmaterial,unlikethefemalewhich 2. 15February 3 May
often repaired the seal with its bill. The female 43.. 1188FFeebbrruuaarryy 1135MMaayy**
was seen cleaning the nest-cavity by throwing 5. 21 February 16May
out a lotofseeds and woody debris. The female 6. 18February 18April**
hornbill used her own excreta, rich in Ficus 78.. 147MMaarrcchh** 1131 MMaayy*
seeds, asmaterialforsealingthecavityentrance. 9. 3March* 16May
The inmateseffectednestsanitationbysquirting 10. 18February 15May
—
theirexcreta outthrough the slit-like opening of * — Thechickfledgedbetweenthisdayand20May
** Abandoned
the cavity entrance.
* - Nestsdiscoveredafterthenestinghadcommenced
Nestingperiod: Thenesting seasonlasted
for about three months, between February and female of the focal nest had tail feathers
Mayinthe studypopulationoftheMalabargrey throughout the nesting period. These could be
hornbills. The nesting period could be seenwhilethebirdwasejectingthefaecalmatter
distinguished into two main phases: the pre- through‘the slit. However, rectrices had been
hatching andthepost-hatchingphase. However, collected from the midden of six nests during
each phase in turn has been further divided into the preliminary study in 1993. Thus, it is likely
3 sub-phases (fortnightly) for analysis. The that the moult in this species is partial.
nesting period in the focal nest was 86 days, Food delivery by the male hornbill: The
commencing fromFebruary 18 (incarcerationof focal nestwas observed for a total of 161 hours
the female) to May 15 (emergence ofchick and and 45 minutes. All through the nesting period,
female from the nest). The mean duration ofthe themaleprovisionedtheincarceratedfemaleand
nesting period was 86 days (± 2.7 S.D.; N=4). later,theyoungalso. Atotalof2,397 fooditems,
Inthefocalnest,theyounghatched40days which included 1 1 kinds of fruit, 5 species of
after the incarceration of the female. The post- vertebrates, and at least 8 types ofinvertebrates,
hatching phase was 46 days. Only one chick including 6 types of insects, were delivered by
appeared to have fledged. The female and young the male (Appendix). Lipid-rich fruits
brokeoutofthenesttogether.Detailsofthenesting predominated in the diet of the incarcerated
period in the tennests are given in Table 1 hornbills, constituting 36.9% of the food
Clutchsizeand moulting: Theclutchsize delivered.OtherfoodcategorieswereFicus26%,
in the breeding population could not be sugar-rich fruits 22.6%, and animal matter
determined. In the focal nest, only one young 13.8%. If there were several items, these were
was seen. One nestwhen examined on March regurgitated one by one. Large fruits and
1
1994,hadonlyoneegg.A weeklater, therewere vertebrate prey were usually brought as single
two eggs in this nest. The female resealed the items.
cavity entrance andbred successfully. Thenumberoffooditemsdeliveredpeaked
Flight feathers were collected from the during the pre-hatching phase, and declined
midden occasionally, particularly in the month thereafter, being minimum before the fledging
ofApril. The rectrices were neverfound andthe of the young. The frequency of lipid-rich and
18 JOURNAL, BOMBAYNATURAL HISTORYSOCIETY. 97(1). APR. 2000
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BREEDINGBIOLOGYOFTHEMALABARGREYHORNBILL
APPENDIX
PLANTANDANIMALFOODDELIVEREDATTHENESTBYTHEMALEMALABARGREYHORNBILL
A:Plantfood(fruit) A:Plantfood(fruit)(contd.)
S.No. Species Habit Number Number S.No. Species Flabit Number Number
(Family) inpre- inpost- (Family) inpre- inpost-
hatching hatching hatching hatching
phase phase phase phase
Sugair-richFruit 17. Knemaattenuate
1. Ficusspp. (Myristicaceae)* Tree
(Moraceae) Tree/ 443 123 18. PolyaIthiasp.
Strangler (Annonaceae)+ Tree - -
2. Mimusopselengi
(Sapotaceae) Tree 17 _ OtherFruits
3. Brideliasp. 19. Strychnos
(Eupborbiaceae) Climber 417 13 nux-vomica
4. Elaegnusconferta (Loganiaceae)* Tree -
(Elaegnaceae) Climber 4 _
20. Unidentified**
5. Linocera
intermedia —
(Sapindaceae)+ Tree + — Foundinthemiddenofthefocalnest
6. S(Myyzrytgaicuemaes)pp+. Tree _ *** — TFeonunsdpeicnitehsewmhiodsdeensseeodfsowtehreer(fnoounn-dfoicnaslm)anlelstnsumbers
7. Filiciumdecipiens inthemiddens(threewerefoundinthemiddenofthe
(Oleaceae)* Tree _ focalnest)
8. Zizyphus
B:AnimalFood
nummularia
Vertebrates
(Rhamnaceae) Shrub 61
9. pGelnytcaopshmyilsla 1. Youngbird
(Rutaceae) Shrub 11 _ 2. Snake
3. Lizard(Calotessp.)
4. Gecko
Lipid-richFruit
10. Uvariasp. 5. Frog
(Annonaceae) Climber 510 63
Invertebrates
11. Neolitseasp.
(Lauraceae) Tree 173 52
12. Cinnamomumsp. 1. Beetle
2. Cricket/Grasshopper
(Lauraceae) Tree
13. Perseamacarantlia 3. Cicada
(Lauraceae)* Tree _ 4. StickInsect
5. Caterpillars
14. L(iLtasueraacspe.ae + Tree _ _ 6. Wingedinsect(wasp,termite,etc.)
7. Millipede/Centipede
15. Beilschmediasp.
(Lauraceae) Tree _ 19 8. Scorpions
16. Myristica
dactyloides Totalnumberofanimalfooditemsdeliveredduringthe
(Myristicaceae)* Tree nestingperiod=491.
non-figsugar-richfruitswassignificantlyhigher matterdeliveredwasgreaterinthepost-hatching
in the pre-hatching phases (Mann-Whitney U phase(Mann-WhitneyUtest,U=41,p=0.047for
test, N=16, U=24, pO.OOl andU=36, p<0.001, invertebratesandU=64,p=0,014forvertebrates;
respectively). Figs were eaten consistently Fig. 1). Within the pre-hatching phase, the
throughout the nesting period. The frequency frequency of lipid-rich fruits was significantly
(number per hour of observation) of animal higher than the other types (Kruskal-Wallis
JOURNAL BOMBAYNATURAL HISTORYSOCIETY, 97(1), APR. 2000 19
BREEDINGBIOLOGYOFTHEMALABARGREYHORNBILL
Minutes/hour
Number/hour
Minutes/hour
Fig. 1: a. Time spent at nest by the male, b. Visiting rate ofthe male, and c. Frequency ofdifferent food
items delivered to the inmates by the male during the nesting period.
20 JOURNAL BOMBAYNATURAL HISTORYSOCIETY. 97(1). APR. 2000
.
)
BREEDINGBIOLOGYOFTHEMALABARGREYHORNBILL
X2=13.48, df=3, p<0.001), while in the post- were other inquisitive visitors to the nest, but
hatching phase, animal food was significantly were apparently disregardedbythe incarcerated
greater (%2=23.26, df=3, p<0.001). female.
Time spent at nest and visitation rate of
the male: The time spent and the visitation rate Discussion
of the male hornbill was influenced by the
number andtype ofitems delivered. Time spent The 32 species of Oriental hornbills are
(minutes per hour of observation) was essentiallyforest-dwelling,arborealbirds(Kemp
significantly higher (Mann-Whitney U test, 1988, 1995). These species, including the
U=38, p<0.01) in the pre-hatching than in the Malabar grey hornbill, are long-lived, and have
post-hatching phase, as a greater number adistinctandrelatively longnestingperiod. The
(69.5%) ofsmall fruits (< 1.5 cm) was delivered nestingperiodoftheMalabargreyhornbilllasted
(each had to be regurgitated individually). The an average of86 (± 2.7 days) during this study.
visitation rate did not differ between the phases The success ofthisbird as a rainforest specialist
(Fig. 1). — canbeattributedto its life-history strategies (the
Feeding habits evidence from long and peculiar nesting behaviour), and the
middens: Supplementarydatafromthemiddens adaptation in food habits.
of the ten nests showed that nine additional Predation ofadult Malabar grey hornbills
species of fruits were consumed by the by animals other than man is rare. Even during
incarcerated hornbills (e.g. Strychnos nux- the vulnerable period of incarceration, the
vomica, Litsea sp., Persea macarantha, see chances ofpredation are low, because the nest-
Appendix).Afewseedsoftenunidentifiedplant cavity entrance is sealed, and the female with
specieswerecollectedfromsomemiddens.There herlarge,armouredbillcanprotectthenestfrom
was no significant difference between the pre- intruders. This protection, along with the cavity
andpost-hatchingphases inthe frequency ofthe nesting habit, can be the reason for the long
lipid-richfruitseedscollectedinthemidden. The incubationperiod ofthese birds.
frequencyofnon-figsugar-richfruitseedsinthe Overall, the nesting periocl and food
midden was found to be significantly greater in deliverybytheMalabargreyhornbill inthearea,
the pre-hatching phase (Mann-Whitney U test, as in the case of great pied hornbill Buceros
(
N=21, U=T16, p=0.007). bicornis), seems to be associated with fruiting
PredationonMalabargreyhornbilland phenology, and the onset of the southwest
nestintrusion:TwocasesofmortalityofMalabar monsoon (Kannan 1994). Studies in Thailand
grey hornbills were recorded. The first was ofa (Poonswad et al. 1988) have found the nesting
young birdfoundtowards the endofthe nesting of hornbills to commence and terminate later
periodduringthepreliminarystudyin 1993.The thaninthis region, probablybecause ofthe later
secondwaspresumablyanadult,whoseremains monsoon.Hornbillssubsistonanarrayofdiverse,
were found in the middle ofthe nesting period locally rare, tree species (e.g. members ofthe
in 1994, close to a regularly monitored nest Lauraceae; Kannan and James 1999). The
which hadbeen abandoned five days earlier. nesting period coincides with the peak in fruit
The focal nest was once visited by three availability, as shownby the fruiting phenology
hill mynas (Gracula religiosa) thatflewaway at study of Kannan and James (1999). Large
the approach of the male hornbill. A Malabar numbers of rainforest trees of the families
giant squirrel Ratufa indica) and the dusky- Lauraceae, Burseraceae, and Myristicaceae {op
(
striped palm squirrel (Funambulus sublineatus cit.) contribute to the abundance offruit.
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BREEDINGBIOLOGYOFTHEMALABARGREYHORNBILL
Lipid-richfruitsformedthemostabundant phase. This was probably compensated by the
componentofthefooddelivered.Thecoincidence nutritive quality (lipid-rich fruits and animal
ofnestingwithpeakinlipid-richfruitavailability food), andlargersizeofthe food itemsdelivered
couldbeasaresultoflong-termco-evolutionary (eg. fruits ofMyristica sp., Beilschmedia spp.).
process (McKey 1975). The high lipid content There was a drastic fall in the number ofvisits
of these fruits may be necessary to meet the during the last few days of the nesting period.
requirements of the nesting, moulting, and Welty(1982)proposedthatthe steady decline in
growing birds (Snow 1981). feeding frequency may be a naturally evolved
Protein, carbohydrate, and water is strategy of the parent to encourage the nearly-
obtained from sugar-rich fruits (including figs) fledged young to leave the nest.
and animal matter, which supplement the lipid- The differences in the food delivered
rich diet of the nesting hornbills. Notably, the during the nesting period can be explained by
Malabar grey hornbill fed less on Ficus fruits one or a combination of the following factors:
(26%) than the great pied, oriental pied (i) It couldbe related to the availability offruits
(Anthracoceros coronatus), and wreathed duetotheusuallyhighseasonalandsynchronous
{Acerosundulatus)hornbills(KannanandJames fruiting of tree species bearing lipid-rich fruits
1997, Tsuji 1996). The smaller white-throated (Snow 1981, Leighton and Leighton 1983,
brown hornbill (Ptilolaemus tickelli), however, Kannan and James 1999), while the sugar-rich
is shown to feed less on figs. fruits are available all through the year.
Smaller-sizedhornbills are able to feedon Community fruiting patterns in the study area
awiderrange offruitand animal food, probably were foundtobe largely determinedby thetrees
duetotheirsmallerbodysizewhichenablesthem producing lipid-rich fruits like Lauraceae,
toaccesseventheunderstoreyshrubspecies,thus Annonaceae, which form a major proportion of
reducing the predominance of any one type of tree species in the area (Kannan 1994). It was
food. The Malabar grey hornbill consumes a observedthat certain fruits such asAlseodaphne
greater variety of sugar-rich, particularly semecarpifolia Litsea sp., and Persea
,
understorey fruits, as well as fruits ofsmalltrees macaranthci whichwere common and abundant
,
and climbers, unlike the larger syntopic great in the middens during the preliminary study in
pied hornbill which prefers large, canopy and 1993, were absent in 1994. So, inter-annual
emergent trees (Kannan 1994). differences in fruiting patterns, and intra-
A wide range offood items are fed to the seasonal staggering in the fruiting patterns of
nest inmates. The kind of food delivered the Lauraceae in the rainforests is likely to play
influenced the visitation-rate, and the time spent a major role in the nesting and nesting success
at nest by the male. The time spent was of the hornbills (Snow 1981, Leighton 1982,
significantly higher in the pre-hatching phase LeightonandLeighton 1983, Kannan andJames
astherewasagreaternumberofsmallfruits(both 1999).
lipid- andsugar-richfruits, i.e., 61% ofall small (ii) Anotherpossibility is that the hornbill
fruits) delivered at the nest. The time spent at selectshighqualitynutritivefoodforthegrowing
thenestdecreasedtowardstheendofthenesting chicks in the post-hatching phase, feeding them
period, when large fruits and animal food were largelylipid-richfruitsandanimalmatter, which
brought forthe inmates anddeliveredas a single may be of co-evolutionary significance. The
item per visit. The visitation rate did not differ increaseddeliveryofanimal foodtowardthe end
between the phases, though the number offruits ofthe nesting season may reflect an increase in
deliveredpervisitdecreasedinthepost-hatching abundance ofinsect prey in the forestjust after
22 JOURNAL BOMBAYNATURAL HISTORYSOCIETY, 97(1), APR. 2000
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BREEDINGBIOLOGYOFTHEMALABARGREYHORNBILL
the rains. The supplementation of high quality the Malabar grey hornbill. Hornbills play an
animal matter, however, coincides with the important role in the dynamics oftheir habitats
hatching of the chick and may provide the because of their specialised frugivorous habits
growing chick with essential nutrients. (McKey 1975, Snow 1981, Leighton 1982) and
(iii) Hombills are known to be territorial, as effective dispersers of many tree species
ranging between 3 to 30 km2 (white-throated (Kinnaird 1998, Whitney et al. 1998).
brown and great pied hornbills, respectively) The Malabar grey hornbill, like other
dependingonthesizeofthebird(Poonswadand members of the family Bucerotidae, act as
Tsuji 1994). Seeds ofsome fruits (eg. Filicium keystone species in the range ofits distribution
decipiens, Polyalthia sp.) were found in the (Gilbert 1980).Thisendemic,specialistfrugivore
middens ofonly a few nests, probably because ofthe rainforest ofthe Western Ghats plays an
these fruiting trees were abundant in the important role in the dynamics of the moist
territories of the hornbills inhabiting those evergreen forest it inhabits, dispersing the seeds
nests. ofafewrarerainforesttreespecies. Conservation
of their habitat is imperative as they have
Conclusion specialised feeding and nesting requirements
(Mudappa and Kannan 1997).
The Western Ghats have been identified
as one ofthe biodiversity hotspots in the world ACKNOWLEDGEMENTS
(Myers 1990, 1991). However, large scale
deforestation for dam construction, agriculture Theresearchwassupportedbyagrantfrom
and other developmental activities has resulted the Oriental Bird Club, U. K. I thank R. Kannan
inthe lossofover40%forestcoverinthe last70 for guidance and encouragement and Ganesh,
years (Chattopadhyay 1985, Menon and Bawa my assistant, for help in field work. I thank the
1997). This in turn has restricted the range of Tamil Nadu Forest Department for permission
many species, includingmany endemics suchas to carry outthe study.
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