Conservation status, feeding guilds, and diversity of birds in Daroji Sloth Bear Sanctuary, Karnataka, India

The present study was carried out to investigate the importance of habitat quality for the diversity, distribution, and abundance of avifauna in Daroji Sloth Bear Sanctuary, Ballari District from February 2015 to January 2016. A total number of 189 species of birds, belonging to 62 families and 18 orders were recorded during the survey. A family-wise analysis showed that the families Accipitridae (12 species), followed by Muscicapidae (11 species), Ardeidae & Alaudidae (8 species each), and Cuculidae (7 species) dominated the avifauna of the region. The residential status of birds revealed that 74% (140 species) were resident, 23% (44 species) were winter, 2% (3 species) were summer and 1% (2 species) was passage migrant’s species. The study resulted in the recording of fives globally Near Threatened category, viz, Painted Stork, Black-headed Ibis, Oriental Darter, River Tern, and Pallid Harrier; and two Vulnerable species, viz, Yellow-throated Bulbul and Woolly-necked Stork. The feeding guild analysis revealed that the insectivorous guild has the most number of recorded avian species (33%, 63 species), followed by carnivorous (31%, 58 species) and least by nectarivorous (1%, 2 species). This study provides baseline data for monitoring the avifauna in the sanctuary and demonstrates the importance of the area in bird conservation. The study also highlights the negative impact of anthropogenic activities as the main cause for the loss of diversity of both birds and their habitat and the urgent need to conserve this biodiversity-rich area with long-term monitoring programs.


INTRODUCTION
Birds are good indicators of the ecological status of any ecosystem (Bilgrami 1995). Ecologically; birds are of tremendous importance because of their key roles as pollinators and agents of seed dispersal (Nason 1992;Bibi & Ali 2013). Changes in their population, behavior patterns, and reproductive ability have been used mostly to examine the long-term effects of habitat fragmentation (Harisha & Hosetti 2009). Given the significance of birds for conservation planning and environmental assessments, there is a need for a better ecological understanding of the role of bird diversity patterns and community structure in conservation decision-making (Kati & Sekercioglu 2006).
Forests attract a significant number of birds because they provide suitable habitats for most birds, especially those birds associated with vegetation, and for most, the existence of trees is a vital component of their life cycle. The birds' level of interest in various forests depends on the age of the stand. The composition of bird species is highly related to the vegetation structure of forests (Robertson & Hackwell 1995). The habitat type and structural complexity influence species diversity and the inter-relationship between vegetation and avian population (MacArthur & MacArthur 1961).
Approximately, 9,990 bird species are recorded on our planet and the Indian subcontinent is home to 1,263 bird species (Praveen et al. 2016a), constituting about 12% of the world avifauna. Of these, approximately 531 species of birds have been reported from Karnataka. Due to geographical variation, the Deccan Plateau region of India possesses great diversity in agricultural as well as wild floral and faunal diversity. Therefore, understanding the diversity and structure of bird communities is essential to delineate the importance of regional or local landscapes for avian conservation (Kattan & Franco 2004).
Very few avifaunal works have been done in Daroji Sloth Bear Sanctuary (DSBS). Previously, Neginhal et al. (2003) reported 90 species of birds. Later, Harisha (2013) recorded 135 bird species belonging to 43 families under 16 orders from 2009 to 2012. Except for these earlier reports, no detailed long-term studies have been made on the biodiversity of birds in the study area. In this context, the present study was undertaken to highlight the status, composition, feeding guilds, and diversity of birds of DSBS, Ballari District, Karnataka.

Study Area
Daroji Sloth Bear Sanctuary is located between Hospet and Sandur Taluk of Ballari District of Karnataka and is spread over 82.72 km 2 (Figure 1). It is about 50 km from Ballari and about 15 km from the World Heritage Site Hampi. In October 1994, the Government of Karnataka declared 5587.30 ha of the Bilikallu Forest Reserve as Daroji Sloth Bear Sanctuary. After 15 years, in October 2009, the government added 2685.50 ha of the Bukkasagara Forest Reserve to the sanctuary. This resulted in the overall area increasing from 5587.3 ha to 8272.8 ha. It lies between 15.269 0 N and 76.571 0 E with an average elevation of 521 m, temperature of 20-46°C & annual rainfall of 450-500 mm. It is a strewn hillock that stretches between Daroji of Sandur Taluk and Ramasagar of Hospet taluk in Ballari District (Image 1, 2). The sanctuary has rich floral and faunal diversity. The flora of this sanctuary is primarily dry deciduous scrub and southern thorn forests. The typical species of scrub jungle, Grewia damine is found to be the most abundant species of the plant followed by Senegalia catechu and Albizia amara in the habitat. It has a very stable population of Sloth Bears and they reside in the numerous caves found in the hillocks within the sanctuary. Leopards, monitor lizards, mongoose, pangolins, and Star Tortoises are some of the other animals that abound in the sanctuary.

Sampling method
A study on avifaunal diversity was carried out from February 2015 to January 2016. The line transect method was used, as the habitat of the study area was of open type (Sutherland et al. 2005). Six line transects were set up, which were approximately 500m in length and 20-30 meters in width. The transect line was walked at a constant pace for approximately 30 minutes. Twelve field visits (1 visit per month) were conducted observing the status and diversity of birds. The field surveys were conducted in the morning (0600-1000 h) and the evening (1600-1900 h), depending on the season when birds were most active. Birds were observed using the Olympus binoculars (10x50), and were identified with the help of field guides (Ali & Ripley 1983;Grimmett et al. 2011) and were given standardized common and scientific names (Praveen et al. 2016b). The residential status of the birds was worked out and birds are grouped under different categories like resident, summer, passage, and winter migrants or visitors depending on their timing and duration of occurrence (Grimmett et J TT al. 2011). The International Union for the Conservation of Nature (IUCN) Red List status was additionally used to compare the local status with the global status. During the surveys, other information or threats to bird conservation were noted. The data recorded in each survey were kept separate, and later analyzed for relative abundance based on the frequency of bird sightings and are categorized, as very common (Vc) sighted >10 times; common (Co) sighted 7-9 times; uncommon (Uc) sighted 3-6 times; rare (Ra) sighted 1-2 times (MacKinnon & Phillipps 1993). Feeding guilds were classified based on direct observations and available literature (Ali & Ripley 1987). The relative diversity (RDI) of families was calculated adopting the following formula (Torre-Cuadros et al. 2007): Number of bird species in a family RDI = ______________________________ X 100 Total number of species

Avian community structure as per residential status and relative abundance
The analysis of data on the residential status revealed that out of 189 species, 140 (74%) were resident, 44 (23%) winter, 3 (2%) summer, and 2 (1%) passage migrants respectively ( Figure 2). The occurrence of a significant number of winter migrant species can be attributed partly to the study area being on the Central Asian Flyway and serving as a wintering and stopover site for migratory birds that breed in the Palearctic region (Kumar et al. 2016). The spatio-temporal distribution and relative abundance of avifauna in any given habitat are determined based on the quality and quantity of food available as the major factor (Wiens 1989; Ma et      Jha 2013). The analysis of relative abundance based on the frequency of sightings indicated that 89 species were common, 49 were uncommon, 28 were very common and 23 were rare species, which accounts for 47%, 26%, 15%, and 12% of the frequency of distribution in the study area ( Figure 3).

Avian community structure as per habitat
From the earlier studies undertaken elsewhere, it is evident that variation in vegetation structure influences species distribution (MacArthur et al., 1962;Karr & Roth, 1971;Pearman 2002) within a habitat. Of the 189 species recorded, 139 species were associated with terrestrial habitat and 50 species were wetlandassociated, which account for 74% and 26% of total bird species recorded (Table 1). Wetland characteristics like size, water depth, quality of water, trophic structure, and presence of suitable roosting and nursery sites influence the abundance and diversity of birds (Wiens 1989;Mukherjee et al. 2002;Ma et al. 2010). During the present study, wetland birds such as ducks, herons, egrets, cormorants, grebes, storks, jacanas, and kingfishers, which were observed to feed on aquatic organisms (fish, amphibians, invertebrates, etc.,) at different water depths available in the wetlands and adjoining agriculture fields and marshy area.

Feeding guild structure
The diversity of avifauna in the study area may be due to the presence of a wide spectrum of food niches. The different species of birds occupying a particular feeding guild and space have evolved specialized foraging strategies to explore and obtain food resources efficiently and thus to reduce competition among diverse species (Nudds & Bowlby 1984;Jose & Zacharias 2003). An analysis of the feeding guilds of these birds revealed that 33% (63 species) were insectivorous and 31% (58 species) were carnivorous, 21% (40 species) were omnivorous, 9% (17 species) were granivorous, 3% (5 species) were frugivorous, 2% (4 species) were nectarivorous and 1% (2 species) were herbivorous respectively (Figure 3). Due to their specialized diet and low availability of preferable food resources, the nectarivores and piscivores are traditionally less represented (Wiens 1989). Occurrence of a significant number of insectivorous bird communities indicates that the area consists rich insect diversity as well as less disturbance in the form of forest fire consequences (Gregory et al. 2001) and also play a major role as important bio-control agents of insect pest of agriculture, horticulture, and forest ecosystem (Mahabal 2005;Thakur et al. 2010 The presence of carnivorous species in the study area, which is primarily influenced by the availability of food sources, however, indicates the abundance of their prey. Prey bases such as small birds, lizards, snakes, rats, are among the food sources for carnivores in the area. The study area also supports four species of nectarivorous birds which include, Thick-billed Flowerpecker Dicaeum agile, Pale-billed Flowerpecker Dicaeum erythrorynchos, Purple-rumped Sunbird Leptocoma zeylonica, and Purple Sunbird Cinnyris asiaticus have been regularly seen from the area.

Conservation status of avian fauna
To understand the importance of a site it is necessary to examine the significance in terms of the presence and abundance of species (Bruford 2002 It is evident from earlier studies that the landscape with diverse habitats provides opportunities for diverse avian fauna assemblages (Karr & Roth 1971). The study area has been selected as an important bird area in India (IBA), as it maintains a significant thriving population of a globally threatened and vulnerable species, i.e., Yellow-throated Bulbul with its fragmented population is restricted to the southern Deccan Plateau of India (Birdlife International 2001). Earlier recorded sighting (Allen 1908) of 20 pairs was in June 1901 in the Ballari District. Kottur (2014) observed this species around Matanga Hill in Hampi, Daroji Sloth Bear Sanctuary, and Sannapura Forest in the Koppal District. This species has been considered as Vulnerable because of threats caused due to degradation of its scrub forest habitats by various anthropogenic activities such as total clearance of vegetation, excessive wood-cutting, cattle-grazing and the quarrying of hillocks, etc (Subramanya et al. 1993(Subramanya et al. , 1995Stattersfield et al. 1998).
Daroji Sloth Bear Sanctuary lies in an important biogeographic zone, i.e., Deccan Peninsula with its amazingly diverse vegetation structure and environments not only attracts a variety of resident as well as migratory bird species but also influence their diversity and distribution within the habitat (MacArthur et al. 1962;Karr & Roth 1971;Pearman 2002). Anthropogenic disturbances on forest structure and function are well on record (Bhat & Murali 2001;Chandrashekara et al. 2006) and indicated a negative influence of the anthropogenic intervention on overall bird diversity (Image 3-5). The present study also revealed that the avifauna and their habitat was under threats due to intensive anthropogenic activities, highlighted earlier along with those other disturbances like habitat alternations, construction of roads, firewood collection, and poaching in the forest areas that impacted the environment adversely which intern disturbing many threatened and migratory bird species. Hence, documentation of the bird community and identification of potential threats are the primary concerns of conservation at present.
The data recorded in the present study provides valuable information about the diversity of avifauna of Daroji Sloth Bear Sanctuary, as a baseline data for future EIA studies, and helping in formulating future conservation strategies to improve the forest habitats, which will attract the number of the resident bird as well as migratory species. Further, more long-term scientific studies and monitoring along with local participation needed to understand the ecological status, seasonal wise abundance, and diversity, and conservation of birds in this particular area.