FORKTAIL 26 (2010): 82-85 Breeding behaviour and nest tree use by Indian Grey Hornbill Ocyceros birostris in the Eastern Ghats, India E. SANTHOSHKUMAR and P. BALASUBRAMANIAN The breeding ecology of Indian Grey Hornbill Ocyceros birostris was studied during 2007 and 2008 in Sathyamangalam Forest Division, Eastern Ghats, India. In the breeding season, 32 active nests of Indian Grey Hornbill were recorded. Nesting started early in March and ended in late June. The nesting period averaged 87 days, with the female sealed in the nest cavity for an average of 76 days and the nestlings fledging an average of 13 days after the female emerged. Nest-sealing materials used include the hornbill’s own faeces, mud, cattle dung and tree bark. An average of two fledglings from each nest was recorded. Two of the 32 active nests were predated, a nesting success of 94%. Six tree species belonging to five families were used for nesting; the majority (44%) of nests were in Melia dubia (Meliaceae) making it the most preferred nest-tree species (Ivlev’s selectivity index PI = 0.27). The nest tree dimensions (tree girth at breast height 3±1 m, tree height 23±7 m, nest height 14±7 m, girth at nest height 2±0 m) indicate the average requirements of Indian Grey Hornbill for a suitable nest site. All nests were located in the riverine habitat and hence protection of riverian habitat is emphasised. INTRODUCTION rainfall of 1,000-1,600 mm and mean temperatures of 20-25°C during winter and 30-32°C in summer. Hornbills Bucerotidae are one of the most recognisable Vegetation in the study area varies considerably with groups of birds in the Old World tropics. There are 54 altitude, but dry deciduous and riverine forests species of hornbills in the world (Kemp 1995) and nine predominate at the study site. species occur in India (Ali & Ripley 1987). The Indian As hornbills depend on tree cavities for nesting, an Grey Hornbill Ocyceros birostris, also known as Common intensive search for nest cavities was carried out during Grey Hornbill, is reported to occur in India, Pakistan and breeding season. Cavities of trees being actively used by Nepal (Ali & Ripley 1987). In India it is distributed hornbills are identified by following breeding pairs of throughout the country, excepting for Malabar, parts of hornbills or breeding males carrying food to the nest, as Rajasthan and Assam (Ali 2002). In southern India, this well as by examining midden deposits of seeds below the species is reported to occur in the dry deciduous tracts of nest cavity. Out of a total of 32 active nests located in two the Eastern Ghats and foothill forests of the Western years, 10 were selected for monitoring the activities of the Ghats (Balasubramanian et al. 2005). Hornbills are hornbills at the respective nests from 06h00 to 18h00, secondary cavity nesters, using natural cavities or those giving a total of 720 hours (7 2 hours per nest) spent at the excavated by other birds (Kemp 1995). The breeding nest sites. Details such as number of visits made by the habits of hornbills are unique in that the female of most male and quantity of food items delivered per visit were species seals herself into a nest cavity and leaves only a also recorded from an observation hide situated 10-20 m narrow slit through which the male passes her food until away from the nest, using a pair of 10x50 binoculars. The the nesting period is completed (Kemp 2001). Hornbills food items delivered were classified as vegetable or animal often show high nest-site fidelity, returning to the same food. Seeds from 10 middens below other nests were also nest cavity year after year (Kemp 1978). Patil etal. (1997) collected at regular intervals to identify food items provided some information on the nesting of Indian Grey delivered to the nest inmates and for use in further studies. Hornbill, but a review of literature reveals the absence of Tree species harbouring the nests were identified by using detailed studies on breeding ecology. The present study the local floras and later confirmed at the Botanical Survey was undertaken to assess the breeding behaviour and nest of India, Coimbatore, India. Nest tree features, such as tree preference of Indian Grey Hornbill in a forested tree girth at breast height, tree height, nest height and landscape in the Eastern Ghats. girth at nest height, were recorded for all the identified nests. A preference index (PI) of the nest trees used by Indian STUDY AREA AND METHODS Grey Hornbill was calculated using Ivlev’s Index of Selectivity (Ivlev 1961) (PI = U-A/U+A, where U denotes The present study was conducted during the two utilisation of the species and A denotes availability of successive breeding seasons of March to May in 2007 and corresponding species). Values of PI range between -1 2008, in the Hasanur range (940 m asl) of and +1, where -1 indicates avoidance while +1 indicates Sathyamangalam Forest Division (10°29'-11°43'N highest preference. Availability of the tree species was 76°5 T-77°27'E), Eastern Ghats, India. The Eastern determined within a 1 ha belt transect (10x1,000 m) Ghats forms an important habitat for diverse biota across (used as an alternative for a 1 ha square plot). Availability the east coast of India to traverse the states of Orissa, denotes the number of individuals of a species occurring Andhra Pradesh, Tamil Nadu and parts of Karnataka, in the 1 ha plot. To find out the availability of nest tree areas located within 11°30'-22°N and 76°50/-86°30'E species, the belt transect was located along the riverine along a north-east to south-west strike and covering a habitat of the study area. The 1 ha belt transect was divided total area of c.75,000 km2 (Murthy et al. 1982). The into 100 (10x10 m) plots. All the trees within the belt climate regime is tropical monsoon, with an average annual transect with girth at breast height (gbh) more than 20 cm Forktail 26 (2010) Breeding behaviour and nest tree use by Indian Grey Hornbill in India 83 were recorded. Utilisation indicates the number of to tree. The adults fed the chicks for more than a week, individuals of nest tree species used by the hornbills. but later they started to feed themselves and flew long distances following their parents. During the 720 hours spent at 10 nests to monitor the RESULTS nesting behaviour over two breeding seasons, males visited the nests 1,015 times to feed the nest inmates, an average Nesting behaviour of 17 times per day. At a later stage, after the emergence The nesting season lasted for three months, from March of the female from the nest cavity, she joined the male to to June. The hornbills started to prepare themselves for feed the chicks in the cavities. We recorded the male breeding in early December, when such pre-nesting feeding the nest inmates from just before sunrise at 05h45 behaviour as nest-cavity searching, mating and courtship until after sunset at 18h07. We grouped the observations feeding were recorded. Both male and female hornbills into four quarters, 06h00-09h00,09h01-12h00, 12h01 were noticed peeping into tree cavities, one after the other, 15h00 and 15h01-18h00. Of the total 1,015 visits made and this was often noted and continued until the female by males to the nest, in the first quarter males visited 374 entering into the nest cavity. The male hornbill feeding times (37%), 206 times (20%) in the second, 183 times the female hornbill with food items was recorded, where (18%) in the third and 252 times (25%) in the fourth. the female sat near the nest cavity or perched in some The number of visits was highest in first quarter (37%) tree, giving loud calls until the male arrived and offered followed by the fourth quarter (25%), at the start and end her some food items, and this was also recorded in a of the day. Food items like fruits and insects were fruiting tree. Other rare observations made at the nest regurgitated, brought to the tip of the bill and then tree included the male and female flying some 30 m down delivered, whereas animal items like lizards were carried to the ground, holding tightly onto each other’s bill and in the bill and delivered directly. with a loud clapping sound of their wings. Mating A total of 13,680 food items was delivered to the nest behaviour involving three different pairs of hornbills was inmates at the 10 focal nests. The food items delivered to observed during the study. In all the cases mating took the nest inmates included both vegetable (64%) and place while perching on the nest tree, and it happened animal (36%) matter. Vegetable matter delivered before the female entered the cavity. Once we recorded comprised fruits of 26 plant species belonging to 16 plant a female peeping into a cavity, from where the male pushed families, among which 14 species were identified while her back with his bill, until finally she struggled, entered monitoring the nests for fruit deliveries by the male and the cavity, peeped out and then the male offered her some 12 species from the middens of other nests. Animal matter fruits and perched on the next branch. The female stayed delivered included lizards, birds’ eggs, juvenile birds and in the cavity for 20 minutes (17hl5-17h35) and then, various kinds of insect. with a loud call, came out and joined the male. The next Indian Grey Hornbills compete among themselves morning, the female occupied the nest and the male fed for nest cavities and we observed a pair chasing another her with fruits. In the study area, females entered their pair during nest searching. The other nest competitors in cavity in the first week of March and some late nests were the study area were Rose-ringed Parakeet Psittacula also recorded in April. As soon as the female entered the krameri, Golden-backed Woodpecker Dinopiumjavaiieuse, cavity she started cleaning the nest, and we observed her Common Myna Acridotheres tristis, Jungle Myna throwing out all the waste materials left in by the previous Acridotheres fuscus and Indian Palm Squirrel Funambulus user. Later, the female in the cavity was observed to toss palmarum. All these species were noted to disturb hornbills out the excreta of the chicks with her beak through the during their nest searching and also while the female was nest slit, and herself to turn around and eject her own inside the nest cavity. Nests of Rose-ringed Parakeet, excreta through the slit to form part of the nest midden. Common Myna and Golden-backed Woodpecker were The very next day, the female started sealing the cavity recorded in different cavities of the same nesting tree entrance with her bill using mud, cattle dung and dry tree used by Indian Grey Hornbill. All the nest cavities were bark delivered by the male, and her own fecal matter. found to be occupied later by the competitors after the For the observed 10 nests of Indian Grey Hornbill, hornbills had bred. In addition, Large Brown Flying the nesting period averaged 87 days. Begging calls of the Squirrel Petaurista philippensis and honeybees Apis sp. nestlings were heard on an average of 40 days after the were recorded in two cavities each, after the use by Indian female entered the cavity. Clutch size could not be Grey Hornbill. recorded. The female emerged on average 76 days after Two of the 32 nests were predated during the early sealing in and the nestlings fledged an average of 13 days stages, after egg laying, with both eggs and incarcerated after the female emerged. Two fledglings from each nest female being taken, but the predator was not known. In were recorded; the newly Hedged chicks were smaller in both the cases, feathers of the female, eggshells and broken size than the adults, with fresh plumage and undeveloped sealing material were found in the middens. Thirty of the casques. After their emergence, we observed the chicks 32 nests were successful. making calls and sitting in the top branches of the nest tree or in the neighbouring tree with the adult female, in Nest tree features six of the observed nests. The male brought fruits and fed All 32 active nests identified were in live trees. All nest these to the chicks but after a few minutes both adults left trees were in stream/riverine habitats. The majority of the to forage and returned with fruits that they delivered to nests were in Melia dubia (14) followed by Syzygium cumini the chicks, and then the chicks flew from one branch to (9), Albizia odoratissima (5), Mangifera indica (2), other in the same tree. The next day we observed the Terminalia arjuna (1) and Terminalia bellirica (1). Ivlev’s chicks in the nearest fruiting tree of the nest tree, trying selectivity index indicated that the most preferred nest to forage for themselves on the fruits and flying from tree tree species was Melia dubia (PI = 0.27) (Table 1). 84 E. SANTHOSHKUMAR and P. BALASUBRAMANIAN Forktail 26 (2010) Table 1. Preference index of the nest trees utilised by Indian Grey Hornbill. Number of nests First Second Total no. Number of Preference index Plant species Family year year Re-used of nests trees available / ha PI = U-A/U+A Melia dubia Meliaceae 5 9 4 14 8 0.272727 Syzygium cumini Myrtaceae 1 8 1 9 15 -0.25 Albizia odoratissima Mimosaceae 3 2 2 5 6 -0.09091 Mangifera indica Anacardiaceae - 2 2 37 -0.89744 Terminalia arjuna Combretaceae - i i 64 -0.96923 Terminalia bellirica Combretaceae — i i 13 -0.85714 Table 2. Characteristics of the nest trees and cavities utilised by Indian Nest sanitation observed during the present study was Grey Hornbill. similar to the reports made by Kannan & James (1997) and Hussain (1984) for Great Hornbill and Narcondam Variables MeaniSD Range Hornbill Aceros narcondami respectively. Courtship Tree girth at breast height (m) 3±1 2-5 feeding and grappling of bills with clapping wings observed in the present study are similar to observations of Kannan Tree height (m) 23±7 14-39 & James (1997) for Great Hornbill. Nest height (m) 14±7 6-30 In the study area, Indian Grey Hornbills used tall trees (mean 2±7 m) with large girth (mean 3±1 m) for Girth at nest height (m) 2±0 1-3 nesting. Hornbills using tall trees with large girths were Inner depth of the cavity(cm) 51 ± 11 30-72 also reported in various other studies. Mudappa & Kannan Nest entrance length (cm) 15±5 8-28 (1997) reported Malabar Grey Hornbill nests at an average height of 24 m and the diameter at breast height as 60- Nest entrance width (cm) 12±3 7-15 89 cm. Maheswaran & Balasubramanian (2003) reported a mean tree height of 36±6 m and 283± 101 cm width for The number of nest trees used in the first year was Malabar Grey Hornbills. Kinnaird & O’Brien (1999) nine involving three tree species (.Melia dubia, Syzygium reported a mean height 40±10 (m) and a mean width cumini and Albizia odoratissima), and in the second year 117±41 cm in diameter for nest trees of Sulawesi Red- 23 involving six tree species (three as in the first year plus knobbed Hornbill Aceros cassidix. Mangifera indica, Terminalia arjuna and T. bellirica). In Poaching of Indian Grey Hornbills was not recorded total, 32 nests of six tree species belonging to five families during the study. Cattle grazing and lopping of branches were used for nesting. The majority (44%) of nests were of hornbill food plants for feeding livestock is the major in Melia dubia (Meliaceae). Re-use of nest cavities was problem of the study area. Extension of agricultural observed in the second year (Table 1). Of the nine nests activities in the riverine forests disturbs breeding sites. As recorded in the first year, seven were re-used in the second all hornbill nests were located in trees that are tall, with year. The nest site characteristics were recorded for all a large girth and in riverine habitat, protection and identified nests and are presented in Table 2. conservation of nest trees and the lowland riverine habitat in the Eastern Ghats is recommended. DISCUSSION ACKNOWLEDGEMENTS The hornbill family is characterised by an incubation period closely correlated with body size and by an This paper forms an offshoot of a research project on Ecology of unusually long nestling stage (Kemp 1995). During this Indian Grey Hornbill, sanctioned to Dr. P. Balasubramanian of the study, the nesting period of Indian Grey Hornbill lasted Salim All Centre for Ornithology and Natural History by the for an average of 87 days, very close to the 86 days for the Ministry of Environment and Forests, Government of India. Director, congeneric Malabar Grey Hornbill O. griseus (Mudappa Salim Ali Centre for Ornithology and Natural History encouraged 2000). Indian Grey Hornbills in the study area only used us. We thank the Principal Chief Conservator of Forests, Tamil cavities in the live trees, similar to the observations by Nadu Forest Department, for granting permission to work in Mudappa & Kannan (1997) for Malabar Grey Hornbill the forests. We are grateful to Mr. S. Ramasubramanian, Divisional and Datta & Rawat (2004) for Great Hornbill Buceros Forest Officer, Sathyamangalam Forest Division, for support in bicomis. Wreathed Hornbill Aceros undulatus and Oriental the field. Pied Hornbill Anthracoceros albirostris. Maheswaran & Balasubramanian (2003) reported that 80% of the nest trees used by Malabar Grey Hornbills in the Western REFERENCES Ghats, India, were live. Re-use of nest cavities by Indian Grey Hornbill is reported in this study, and this conforms Ali, S. & Ripley, S. D. 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Santhoshkumar and P. Balasubramanian, Division of Landscape Ecology, Salim Ali Centre for Ornithology and Natural History, Anaikatty Post, Coimbatore 641 108, Tamil Nadu, India. Email: [email protected]