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Avifauna of a Critically Important Montane Forest Corridor: The Kande-Ela Forest Reserve

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Abstract

Sri Lanka's geological history, varied cllmate and topography have shaped its rich speciesdiversity (Abeyrama &Seneviratne, 2017: Weerakoon et al., 2012). lts climate is driven mainly by the monsoonal rains and topography; where there is a south-central mountainous region, which rises to an elevation of 2, 500 m, surrounded by broad lowland plains (Pathirana, 1980). The three distinct avifaunal assemblages of the island-the lowland wet zone assemblage, montane assemblage and dry zone assemblage-are also shaped by the aforementioned factors. The dry zone assemblage has closest affinity to mainland India, and the other two assemblages are characterized by high endemicity and affinity to wetter regions of India, namely the Western Ghats and the foothills of the Eastern Himalayas (Ripley, 1949). The montane avifaunal assemblage is also unique in its high prevalence of relict species; species that do not have a near phylogenetic relative in Sri Lanka or southern lndia (Ripley, 1 949; Wickramasinghe et al., 2O171-Montane avifauna are threatened by many global and local changes. Loss of this unique forest habitat. as a result of deforestation, has been the greatest threat causing fragmentation and eKermination of populations. Only about 6% of montane forests are left on the island (UNESCO World Heritage Center 2016).
AVIFAUNA OF A CRITICALLY IMPORTANT MONTANE
FOREST CORRIDOR: The Kande-Ela Forest Reserve
Sanjaya Weerakkody, Pumudi Gardiyawasam, Chirathi Wijekulathilake, Jeewantha Bandara,
Udari Peiris, Uvini Senanayake, Sahan Siriwardana and Sampath Seneviratnel
Sri Lanka's geological history, varied cllmate and topography
have shaped its rich speciesdiversity (Abeyrama &Seneviratne,
2017: Weerakoon et al., 2012). lts climate is driven mainly by
the monsoonal rains and topography; where there is a south-
central mountainous region, which rises to an elevation of 2,
500 m, surrounded by broad lowland plains (Pathirana, 1980).
The three distinct avifaunal assemblages of the island - the
lowland wet zone assemblage, montane assemblage and dry
zone assemblage - are also shaped by the aforementioned
factors. The dry zone assemblage has closest affinity to
mainland India, and the other two assemblages are character-
ized by high endemicity and affinity to wetter regions of India,
namely the Western Ghats and the foothills of the Eastern
Himalayas (Ripley, 1949). The montane avifaunal assemblage
is also unique in its high prevalence of relict species; species
that do not have a near phylogenetic relative in Sri Lanka or
southern lndia (Ripley, 1 949; Wickramasinghe et al., 2O171 -
Montane avifauna are threatened by many global and local
changes. Loss of this unique forest habitat. as a result of
deforestation, has been the greatest threat causing frag-
mentation and eKermination of populations. Only about 6%
of montane forests are left on the island (UNESCO World
Heritage Center 2016).
1 Laboratory for Molecular Ecology and Evolution, Avian Evolution Node, Department of Zoology and Environment Sciences, University gf
Colombo. Colombo 03.
Three critical montane forest corridors
Presently the montane forests of Sri Lanka are confined to 1,
8OO -2,500m hlgh ridges of the island. The main two ridgef
form an 'anchor-shaped' continuous forest (Figure 1). Thf
continuiW of this stretch of montane forests is maintaincd
by several forest corridors (connectors), which provide unitu
terrupted forest cover and critical passage for wildlife t0
migrate between suitable areas (Sicirec Group, 2009). Thrcl
main connectors maintain this vital continuity (Figure 1). Thf
Kande-Ela Forest Reserve is one of those three connectoff
(Connector 3; Figure 1 ).
Owing to this continuity. montane bird communities havf
managed to move along these forested ridges, facilitatinT
gene flow, which reduces the threat of extinction in the faof
of severe deforestation. Population genetic models cleafly
show that small isolated populations have 10 - 15 fold highfl
risk of extinction than that of large connected populatiotlt
(Grant & Grant, 1996; Price, 2008).
The Kande-Ela Forest Reserve
The Kande-Ela Forest Reserve (KFR) acts as a forestad
connector between the eastern montane forest reserval
$-% ror$ro*
Slta Etiya Forst Rsre
Rffi and Hakg6la Park
Rsere st{f
"ru \:*-*
Sri lrnka and South 3
NaturcRsw
Figure 1. Map of montane wet forests of Sri Lanka. The black dots indicate the three critical connectors (corridors) that maintlh
connectivity between these forests. The Kande-ela forest reserve is highlighted in the overview at the top left corner of the map.
52
Figure 2. Survey trails used for the study. From the starting point, the left-hand side trail leads to the Conical hill, covering the altitudinal
gradient. The right-hand side trail covers the low-elevation forests around the reservoir.
was analyzed and compared with the notes from the KFR and
Meepilimana areas in the Ceylon Bird Club Notes (CBCN) over
the past 1 5 years (from 2000 to 201 5).
Avifaunal Diversity
A total of 92 species of birds had been recorded from the
area surrounding the KFR over the past 1 5 years (CBCN 2000
- 2015). Of that number, 62 species were recorded during
the present survey, which constitute 670/o of the species
recorded in the area.
A high incidence of endemics was one of the k"y obr"ra-
tions of this field survey. One quarter of the list (15 species) is
endemic to the island, which represents 45% of the country's
total endemic species (of a total of 34 species).
We compared the bird list obtained from the current study
with that of the key forest reserves on either side of the
KFR, as described above. The KFR shares the same avifaunal
community, inclusive of endemics. and range-restricted
(montane) forms as the other two adjacent forests. Therefore,
the two otherwise isolated forest bird populations of the
Horton Plains National Park and the Hakgala Strict Nature
Reserve were able to connect with each other through this
narrow stretch of montane forest. As such, the KFR acts as
the main corridor connecting the forest bird communities
of the Hakgala Strict Nature Reserve and eastern montane
forests with the rest of the montane forests of Sri Lanka.
(e.9. Hakgala SNR), the northern reserves (Pidurutalagala) and
the southern reserves (Peak Wilderness and Horton Plans
National Parks) (Figure 1). The geographical makeup of this
connector consists of a man-made reservoir and a stretch of
wet-montane forest. Though most of the surrounding area is
a plateau of about 1, 750m in elevation, several peaks and
ridges are located in the area that reach up to 2, 100m.
Avifaunal Survey
Field surveys were carried out in the KFR from the 17th to 20th
of March 2016. Further observations were undertaken from
April 15th to 19th 2016. Observations were made using two
approaches:
Along the altitude gradient from the water level (of the
Kande-Ela Reservoir: -1, 710m) towards the highest peak in
the KFR (a conical hill: 2, 100m high) and along the shores
of the Kande-Ela Reservoir covering the adjacent forested
areas of the reservoir (Figure 2). Continuous line transects
were conducted along both trails. Additionally, point counts of
25m radius and 5 minute duration were conducted alono line
transects. at 15 minute intervals.
Observations were made using I x 42 (Nikon Monarch and
Vortex Diamondback) and 10 x 42 (Zeiss Victory and Bausch
and Lomb EL) binoculars and a 20 - 60 x 60 (Eagle Optics)
spotting scope. ldentification was made with the aid of a field
expert and published field guides (Harrison, 1999; Rasmussen
& Anderton, 2005; Warakagoda et a1.,2012). Our field dataset
Notes on selected species
Ceylon Bush Warbler
Bradypterus palliseri @ Uvini Senanayake
This endemic species is classified as being 'Near Threatened'
in the National Red List (MOE,2012). lt is a relic species
confined to the mcuntains of Sri Lanka at an elevation of
over 1, 500 to 2, 500m (Ripley 1949). The closest relatives of
this species are found in the Eastern Himalayas. These shy,
skulking birds inhabit the dense undergrowth of mountarn
forests. Yet, the Ceylon Bush Warbler is a common snecipc
in the KFR, especially above 1, 800m.
Dusky-Blue Flycatcher
EL t r r tyias sor dtdus) @ Thushara Siriwardana
An endemic bird, classified ats br-.ing 'Near Threatened', it is
confined to the hills above 1. 200rn (MOE 2012\ and occa
sionally descends to lower elevations (Henry, 1g7g). lt is a
common species in the KFR.
Kashmir Red-breasted Flycatcher
This is a highly range restricted, globally threatened, migrant
endemic to South Asia (MOE, 2012; Rasmussen and
Anderton, 2005). lt is an uncommon winter migrant to Sri
Lanka as well and is found in the Central Hills at about 1,
200m. lt is classified as being 'Vulnerable'. In the KFR, we
encountered this species only in a low-elevation forest of
approximately 1, 750m.
54
Grey-Headed Canary Flycatcher
This is a vulnerable breeding resident of the montane /()r ),
restricted to above 1, 000m (MOE, 2012). lt inhabits forcr,t ,
wooded ravines and gardens (Henry, 1979). We fourrri ,rl
active nest with two eggs during our survey.
Cultctcapa ceylonensts @ Uvini Senanayirl.,,
Ceyfon Whistling Thrush (Myophonus blighi)
An endangered, endemic and one of the rarest of the residert
birds of the island (MOE, 2012). This scarce and shy mountar l
bird is restricted to the hill country at elevations of ovcr
1,5OOm (Henry, 1979) A pair was observed at 1,940m on tlrc
conical hill in the KFR
ficedula subr ubra) @ Saha. S.rrw,rr' 1 r".,
Indian Blackbird
Turdus similtimus O Safran Siri*urOu#
This species is endemic to South Asia and the darrer race of
it, the Ceylon Black Bird (Turdus simillimus kinm:sl) occurs in
Sri Lanka (Rasmussen & Anderton, 2005). lt is iesrrrcteo to
the higher hills, above 1, 500m. In the KFR, it wJs observed at
elevations between 1 ,i6O _ 2, 1OOm.
Yellow-Eared Bulbul
Ceyfon Rufous Babbler (Turdoides rufescens)
Another vulnerable endemtc species (MOE 2012) that is
restncted to the interior western wet zone including the
western slope of the montane zone (Henry 1g7g). tt is one of
the two nuclear species in the mixed_species feeding flocks in
the wet zone jungles (Kotagama & Ratnaweera, 2017). Small
flocks of these Babblers were seen in the lower elevation
forest of the KFR.
ii
It is a 'Near Threatened, endemic species (MOE, 2012) that
rs restncted to the hills above 1, 200 m. However, rt is one of
the commonest birds of the higher friffr. fi inf..,lOits forests,
weltwooded areas, gardens anJorchard, (H;;;, 1979). tr is
the commonest species of bird in the KFR.
Ceylon Hiil White Eye
1:?rTon endemic species of the hills and one of the oldest
White-Eyes of the wortd (Wickramasinnn" "in, 2017). lt
inhabits forests as well as home gardens in the hrgh hills. A
common species in the KFR
Ga rru lax ci nereifrons @ Thushara Siriwardana
This endangered endemic babbler (MOE 2012,)is a wer zone
relic. However, recent research (Seneviratne et ar. rn revtew)
suggests that its taxonomic status may change. Even thorrJllt
the sightings of these babblers .ru nun"r,V rale at nigher
altitudes, it is common in the KFR, esfecially by the rescrvoir.
I
Z o s t e r o p s "rylonr^,"6Gffi
Ashy-headed Laughing Thrush
Pycnonotus peno,l@
55
Ghestnut-Backed Owlet
Gtaucidium castanonotum) @ Udari Peiris
This is one of the two endemic owl species of Sri Lanka' lt is
now confined to the remaining forests of the wet zone and
their adjoining hills up to 2, 000m. lt differs from most of the
owls due to its diurnal habits (Henry, 1979)' lt is often hunting
and calling in broad daylight' The KFR has a good population
of Chestnut-backed owlets. The call of this species was heard
numerous times with some good slghtings during the survey'
.
Conservation concerns
The main threats to the survival of montane forests are defor-
estation, in the form of clearcuts and selective removal of
firewood, and fragmentation. With the growing human
population in the highlands, the demand for land for agriculture'
construction, timber and firewood increases, which leads to
depletion and overexploitation of the nearby forested areas'
Narrow corridors or connectors, such as the KFR, reduces the
isolation of birds and other montane species in tiny pockets'
and allows safe passage from one forest patch to another'
This is critical to maintain viable, less-isolated populations of
our unique montane fauna and flora' Heavy visitation to the
reserve of recreational travelers have degraded the forest' by
them dumping garbage and trampling vegetation' Temporary
constructions, such as food stalls around the reservoir' are
increasingly becoming another problem because they disrupts
the movement of birds and other wildlife across the corridor'
Based on our observations we strongly urge better protectlon
forthe remaining forest connectors/corridors in the mountatns
of Sri Lanka. The survival of biodiversity in small patches of
forests are possible only through these forest connectors
that act as vital corridors for communities - linking the last
fragments of Sri Lanka's endemic-rich montane forests'
56
Acknowledgements
We thank the Hakgala Botanic Gardens and its Curator,
Mr. Sagara Piyasena, for providing logistical support for the
team. Ms. Thejani Perera and Mr. J' R' A' C' Jayakody of
the Department of Zoology provided technical assistance'
Dr. Nishanthi Perera commented on an earlier version of the
manuscript. The Forest Department of Sri Lanka provided the
permits to carry out the survey. The Department of Zoology
and Environment Sciences, University of Colombo provided
funding through its undergraduate field programme'
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Article
Full-text available
Co-occurrence of closely related taxa on islands could be attributed to sympatric speciation or multiple colonization. Sympatric speciation is considered to be rare in small islands, however multiple colonizations are known to be common in both oceanic and continental islands. In this study we investigated the phylogenetic relatedness and means of origin of the two sympatrically co-occurring Zosterops white-eyes, the endemic Zosterops ceylonensis and its widespread regional congener Z. palpebrosus, in the island of Sri Lanka. Sri Lanka is a continental island in the Indian continental shelf of the Northern Indian Ocean. Our multivariate morphometric analyses confirmed the phenotypic distinctness of the two species. Maximum Likelihood and Bayesian phylogenetic analyses with ~2000bp from two mitochondrial (ND2 and ND3) and one nuclear (TGF) gene indicated that they are phylogenetically distinct, and not sister to each other. The two subspecies of the peninsula India; Z. p. egregius of Sri Lanka and India and Z. p. nilgiriensis of Western Ghats (India) clustered within the Z. palpebrosus clade having a common ancestor. In contrast, the divergence of the endemic Z. ceylonensis appears to be much deeper and is basal to the other Zosterops white-eyes. Therefore we conclude that the two Zosterops species originated in the island through independent colonizations from different ancestral lineages, and not through island speciation or multiple colonization from the same continental ancestral population. Despite high endemism, Sri Lankan biodiversity is long considered to be a subset of southern India. This study on a speciose group with high dispersal ability and rapid diversification rate provide evidence for the contribution of multiple colonizations in shaping Sri Lanka’s biodiversity. It also highlights the complex biogeographic patterns of the South Asian region, reflected even in highly vagile groups such as birds.
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The process of speciation in birds can be inferred from the pattern of diversification on islands, especially in archipelagos. The basic model is one of initial differentiation of allopatric populations, with further differentiation taking place at the time that sympatry is established. Differences that evolve in allopatry are reinforced by a regime of divergent selection on the taxa in sympatry arising from ecological pressures and not from reproductive (genetic) incompatibility. A low level of interbreeding (hybridization) at the secondary contact phase and subsequently may occur with little or no fitness loss. Introgressive hybridization has the potential to play a creative role in evolution, facilitating further divergence by enhancing genetic variation and relaxing genetic constraints on particular directions of evolutionary change under natural selection. Hybridization potential may last for many millions of years after two taxa diverge, implying that post-zygotic isolation evolves slowly. The main alternative model of speciation in island birds is the peripatric model. It emphasizes major genetic changes taking place in the founding of a new population by a small number of individuals. There is no direct evidence that would make it preferable to the standard allopatric model for islands.
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The crystallines of the lsland of Sri Lanka is divided into Highland series and Vijayan series and the contact between these two series is a possible Paleo platc boundary. The geological evidence supporting this interpretaticn includes :- The presence of paired metamorphic be!ts-tbe gran~lite facie~ and the amphi- bolite facies. The presence of basic and ultrabasic rocks of probable igneous origin closer to the Highland-Vijayan contact. The copper-magnetite-apatite body and its related rocks. It is possible that ~ninpralisation has taken place at the bouxdary between the two main rock groups. The hot springs of Sri Lanka mainly confined to Vijayan serics and ere n?ostly along the contact. The Submarine Canycn with wall heights 1,350 meters cff the coast of Trinco- rnalee contiggous with the Highland-Vijayan contact. The interpretation is that the boundary between the Highland-Vijayan series was an old subduction zone; where the two plates were moving together. Active volcanism con- tinuous subduction and upliftment have caused the present day HighIan5 series. The rocks of the Highland series comprises of q~artzites, crystalline limestones, gameti- ferous granulites and charnockites. The volcanic rocks are not present today, as they have been eroded away. Both groups are intensely n~etamorphosed and metasoma- tisqd. The Highland series was metamorphosed to the granulite facies and the Vijayan serles to the almandine-arnphibolite facies. 1. Intmroduction and General Geology of Sri Lanka Sri Lanka though an island today, is an int,:gral portion of the carnatic gnessic terrain of the Deccan Peninsula of India only recently severed from the mainland. An attempt has been made in this paper to interpret the Geology of Sri Lanka in terms of plate tectonics. The major geological divisions of Sri Lanka are given by CFigure l).3 The greater part of the country is underlain by crystalline rocks of Pre-Cambrian agc; which are divided into two groups on the basis of metamorphic rank and age. The Highland Series metamorphsscd to granulite facies6 which occupies the central part of Sri Lanko consisting of a succession of gneisses, garnet-silliinanitc-~rap11ii~7-gneisses, quartzites and marbles together with charnockites. Migmatites and granite gneisses are less dcvcloped in the Highland Series.
Evolutionary distinctiveness of lmportant Bird Areas (lBAs) of Sri Lanka: Do the species-rich wet zone forests safeguard Sri Lanka's genetlc heritage?
  • D K Abeyrama
  • S Seneviratne
Abeyrama D. K. and Seneviratne S. S' 2018' Evolutionary distinctiveness of lmportant Bird Areas (lBAs) of Sri Lanka: Do the species-rich wet zone forests safeguard Sri Lanka's genetlc heritage? Ceylon Journal of Science 46:89-99
A Field Guide to the Birds of Sri Lanka
  • J Harrison
Harrison, J. 1999. A Field Guide to the Birds of Sri Lanka .Oxford: Oxford UniversitY Press.
A Guide to the Birds of Ceylon
  • G M Henry
Henry, G. M. 1979. A Guide to the Birds of Ceylon (2"ded')'
2OO5' Birds of south Asia: the Ripley guide
  • P G Rasmussen
  • J Anderton
Rasmussen P. G.' Anderton J. G. 2OO5' Birds of south Asia: the Ripley guide. Washington, DC.
Avian relicts and double invasions in oeninsular India and Ceylon
  • S D Ripley
Ripley S. D. 1949. Avian relicts and double invasions in oeninsular India and Ceylon. Evolution 150-9'
Birds of Sri Lanka: an illJstrated guide. Field Ornithology Group of Sri Lan(a' Sicirec Group
  • S Kotagama
  • G Ratnaweera
Kotagama S. W and Ratnaweera G.2017 Birds of Sri Lanka: an illJstrated guide. Field Ornithology Group of Sri Lan(a' Sicirec Group 2009. Ecological Corridors' Retrieved from http//www.siclrec.org/definit'rons/corridors [Accessed 13
A Brief Overview of the Biodiversity Sri Lanka. ln: Ihe Nationat Red List 2012 of Sri Lanka; Conser irln
  • D Weerakoon
Weerakoon D. 2012' A Brief Overview of the Biodiversity Sri Lanka. ln: Ihe Nationat Red List 2012 of Sri Lanka; Conser irln, St tu" of the Fauna and Flora' Weerakoon, D'K' & S' W["tunOitu Eds., Ministry of Environment, Colombo' Srl Lanka.