Avian
frugivory and seed dispersal of Indian Sandalwood Santalum
album in Tamil Nadu, India
P. Balasubramanian 1,
R. Aruna 2, C. Anbarasu 2 & E. Santhoshkumar 2
1,2 Salim Ali Centre for Ornithology
and Natural History, Anaikatty PO, Coimbatore, Tamil Nadu 641108, India
Email: 1 balusacon@yahoo.com (corresponding author)
Date of publication (online): 26 May 2011
Date of publication (print): 26 May 2011
ISSN 0974-7907 (online) | 0974-7893 (print)
Editor: Richard Thomas Corlett
Manuscript details:
Ms
# o2552
Received
27 August 2010
Final
received 04 April 2011
Finally
accepted 02 May 2011
Citation: Balasubramanian, P., R. Aruna, C. Anbarasu & E. Santhoshkumar
(2011). Avian frugivory and seed dispersal of Indian
Sandalwood Santalum albumin Tamil Nadu, India. Journal of Threatened Taxa 3(5): 1775–1777.
Copyright: © P. Balasubramanian, R. Aruna, C.
Anbarasu & E. Santhoshkumar 2011. Creative Commons
Attribution 3.0 Unported License. JoTT allows unrestricted use of this
article in any medium for non-profit purposes, reproduction and distribution by
providing adequate credit to the authors and the source of publication.
Acknowledgements: We thank the Tamilnadu Forest Department for their support. Thanks
are due to Dr. G Kumaravelu, IFS, former Additional PCCF, Mr. R.K. Ojha, IFS,
Mr. H. Malleshappa, IFS and Mr. K. G. Anand Naik IFS for the encouragement. We
are grateful to Dr. P.A. Azeez, Director, Salim Ali
Centre for Ornithology and Natural History for the encouragement.
Santalum album (Santalaceae) is a medium
sized evergreen tree found in dry forest tracts of the Deccan Peninsula, where
the major sandal growing tracts are located in Karnataka and Tamil Nadu. Sandal is also distributed in parts of
Maharashtra, Andhra Pradesh and Kerala. The species was introduced to several areas of central and northern
India, where it has naturalized and spread. It can grow up to an elevation of 1200m and in rainfall
zones of 300–3000 mm. Flower
panicles appear during December–April and fruiting occurs throughout the
year (Matthew 1991). The fruit is
a fleshy purplish-black globose drupe measuring approximately a centimetre in
diameter. This species also regenerates
from wood suckers. Viable seeds
are produced after five years and dispersed by birds (Asian Regional Workshop
1998). Fire, grazing and
exploitation of the wood for fine furniture, carving and oil are threatening
the species (Asian Regional Workshop 1998). There is much concern regarding over-exploitation due to
smuggling for trade. Santalum album is a Vulnerable (IUCN
2010) and threatened species in southern India (Ravikumar et al. 2000).
Although known as a
bird-dispersed species, very little information is available on frugivory and
seed dispersal of S. album. Biotic dispersal
consists of removal of plant propagules by animal frugivores and the deposition
of seeds away from the source plant. The pulp of fleshy fruits, with the soft, edible, nutritious tissues
surrounding the seeds is a primary food source for many animals, notably birds
and mammals (Howe 1986). These
animals regurgitate, defecate, spit out or otherwise drop the undamaged seeds
away from the parent plants; they are the seed dispersers that establish a
dynamic link between the fruiting plant and the seed-seedling bank in natural
communities (Jordano 2000). Avian
frugivores are considered as the most important seed dispersers in most
ecosystems (Herrera 1995; Stiles 2000). Parrots, some pigeons and finches are seed predators (Corlett
1998). The study of interactions
between avian frugivores and plant species is important for identifying the
roles of individual disperser species play in plant recruitment dynamics, thus
having implications for both theoretical understanding of mutualisms, species
interactions and for applied work, including conservation and restoration
(Jordano 1987; Loiselle & Blake 1999). The present study was carried out to assess the role of
different frugivores in the seed dissemination of sandalwood tree in Tamil
Nadu.
Materials and Methods
Trees with ripe fruits were
selected for field observations. A pair of binoculars was used by the observer, who sat near the
tree, usually 10–15 m away and watched the canopy for recording animal
visits. Extended watches of 3-hr duration were made for a total of 54-hr
in Anaikatty Hills, the Western Ghats and 24-hr in Pachaimalai Hills, the
Eastern Ghats. During the extended watches, the observer noted the name of the
visitor (bird/mammal), frequency of fruit-feeding visits by different species,
and fruit handling behaviour (whether fruit ingested whole or only partly eaten
and seeds dropped). The field
study was carried out between 2006 and 2009 in Anaikatty hills (1105’–11031’N
& 76039’–76047’E), the Western Ghats and
Pachaimalai hills (11015’N & 76038’E), the Eastern
Ghats in Tamil Nadu. Bird’s names
have been followed as per Ali (2002). Observations from Hasanur in
Sathyamangalam Forest Division (11029’–11048’N
& 76050’–77027’E), the Eastern Ghats are also
discussed. The forest type
(Champion & Seth 1968) of the study sites comprise of southern dry mixed
deciduous forest (5A/C3). Predominant trees of the sites include Bauhinia racemosa,
Santalum album, and Chloroxylon swietenia.
Results and Discussion
A total of 217 birds
belonging to eight species visited Santalum album (Table 1) in Anaikatty
Hills, Western Ghats. These
included three species of bulbuls, Pycnonotus sp., Brahminy Starling Sturnus pagodarum, Common Myna Acridotheres tristis, Asian Koel Eudynamys
scolopacea, White-headed Babbler Turdoides affinis and Small Green-Billed
Malkoha Phaenicophaeus viridirostris. Highest proportion of feeding visits was contributed by
Red-whiskered Bulbul, Pycnonotus
jocosus (20.3%) followed by White-headed Babbler (16.7%) and Asian
Koel (16.3%). Among the various avian families, Pycnonotidae (bulbuls)
made the majority of the visits (43.6%) followed by Sturnidae (mynas) (21.6%).
Brown-headed Barbet Megalaima zeylanica was also found to be an important seed disperser in Parali Hills,
the Western Ghats (Balasubramanian et al. 1998). Among the birds, Asian Koel, Brown-headed Barbet, Mynas,
Starlings and Indian Grey Hornbill swallowed the whole fruit. Most often, bulbuls ate the fruit in
piecemeal and dropped the seeds under the canopy itself. Occasionally, small
fruits were swallowed by them.
In the Pachaimalai Hills,
349 birds belonging to three species visited the focal tree during the study
period. Among
the frugivorous birds, the highest proportion of visits was made by the Asian
Koel (50.4%) followed by Common Myna (38.6%), and Rose-ringed Parakeet Psittacula krameri (11%). In addition to
birds, Three-striped Palm Squirrel Funambulus palmarum also visited the plant to
eat fruit. While koel and myna
consumed the whole fruit, parakeets ate the seeds. Three-striped Squirrel ate the pulp and dropped the seeds.
In the Sathyamangalam
Forest Division, Balasubramanian & Santhoshkumar (2009) observed Indian
Grey Hornbill Ocyceros birostris playing an important role in the seed dispersal of S. album. The Indian Grey Hornbill’s diet comprised a
reasonable proportion of Santalum album fruits both in breeding season (7%) and non-breeding season (4%).
Role of Indian Grey Hornbill in regeneration of S. album was evidenced by the
presence of sandalwood seedlings in hornbill’s nest middens. Three percent of the seedlings in
hornbill middens comprised of S. album.
Birds constituted the
principal seed dispersers of Santalum album. Except squirrels no other mammals were foraging on S.album fruit crops during this
study. Most of the natural
seedlings of sandal were found growing in the middle of thorny bushes, where
the birds seem to have dropped the seeds. Birds that are beneficial to sandalwood dispersal and regeneration were
Koel, Common Myna, Brahminy Starling, Brown-headed Barbet, White-headed Babbler
and Indian Grey Hornbill. These
species visited the fruit crop more frequently and swallowed the fruit
wholly. Hence, these species could
be considered as major seed dispersers. Asian Koel seems to have preference to sandal fruits. Bulbuls could not swallow the whole
fruit, due to their smaller beak and narrow gape. They appear to play a minor role only. Parakeets did not play any role in seed
dispersal. They consumed the
fruits mainly to digest the seeds and hence considered as seed predators. Green-billed Malkoha made very few
visits, thus contributing only a minor role.
Sustaining the Asian Koel
population will ensure the regeneration of sandal trees in the forests. Efforts need to be undertaken to
provide a healthy habitat for the seed dispersing bird species such as koel, as
the population of Sandalwood tree is drastically dwindling in the wild.
REFERENCES
Ali, S. (2002). The Book of Indian Birds, 13th Edition, Oxford University Press, Oxford, 326pp.
Asian Regional Workshop (1998). Conservation and
Sustainable Management of Trees, Vietnam: Santalum album. In: IUCN 2010. IUCN Redlist of Threatened Species. Version
2010.2. www.iucnredlist.org.
Balasubramanian,
P., S.N. Prasad & K. Kandavel (1998). Role of birds in seed dispersal and
natural regeneration of forest plants in Tamil Nadu, Technical Report 7, Salim
Ali Centre for Ornithology and Natural History, Coimbatore, India, 43pp
Balasubramanian,
P. & E. Santhoshkumar (2009). Final Report of the Ecology of Indian
Grey Hornbill, Ocyceros birostriswith special reference to its role in seed dispersal in southern Eastern Ghats,
Salim Ali Centre for Ornithology and Natural History, Coimbatore, India, 74pp.
Champion,
H.G. & R. Seth (1968). A revised survey of the forest types of
India, Managers Publications, New Delhi.
Corlett,
R.T. (1998). Frugivory and seed dispersal by
vertebrates in the Oriental (Indomalayan) region. Biological Review 73: 413–448.
Herrera,
C.M. (1995). Plant-vertebrate seed dispersal systems in
the Mediterranean: Ecological, Evolutionary, and Historical Determinants. Annual Review of Ecology and Systematics 26:
705–27.
Howe,
H.F. (1986). Seed dispersal by fruit eating birds and
mammals, pp. 123–190. In: Murray, D.R. (ed.). Seed Dispersal. Academic Press, Sydney, Australia.
IUCN
(2010). Santalum album (Sandalwood), IUCN Redlist of Threatened
Species. Version 2010.2. www.iucnredlist.org.
Loiselle, B.A., & J.G. Blake (1999). Dispersal of melastome
seeds by fruit-eating birds of tropical forest understory. Ecology 80: 330–336.
Jordano, P. (1987). Patterns of mutualistic
interactions in pollination and seed dispersal: connectance, dependence
asymmetries, and coevolution. American Naturalist 129: 657–677.
Jordano, P. (2000). Fruits and frugivory, In:
Fenner, M (ed.) Seeds: the ecology of regeneration in plant communities, 2nd Edition. CABI Publications, Wallingford, UK, 125–166pp.
Matthew, K.M. (1991). An Excursion Flora
of Central Tamil Nadu, India. Oxford & IBH Publishing Co. Pvt. Ltd, New
Delhi, 647pp.
Ravikumar, K., D.K.
Ved, R.V. Sankar & P.S. Udayan (2000). 100 Redlisted Medicinal Plants of Conservation Concern in south
India, Foundation for Revitalization of Local Health Traditions,
Bangalore, 76pp.
Stiles, E.W. (2000). Animals as seed dispersers, pp. 111–124.In: Fenner, M. (ed.). Seeds: The Ecology of Regeneration in Plant Communities. CABI, Wallingford, UK.