Status and habitat preference of White-bellied Shortwing Brachypteryx major in the Western Ghats (Kerala and Tamilnadu), India

White-bellied Shortwing is a globally threatened species found in the Western Ghats of India. There have been few records of this species over the past 119 years and its population is thought to have fallen due to habitat loss and fragmentation. The present study was conducted to assess the habitat preferences and distribution of this species in the Western Ghats of Kerala and Tamilnadu states as a prelude to a long-term study on the biology and causes of decline of this species. Several areas across varying vegetation type and altitude were surveyed after an intensive reconnaissance. There were 214 sightings from evergreen and shola forests during the study. They were found to prefer shola forests to other vegetation types. The species was also found in pine, wattle and tea plantations near shola forests. Although it was found to prefer an altitude above 1,500 m, it was also found in shola forests between 1,000 and 1,500 m elevations. White-bellied Shortwing was found to occupy an elevation range from 1,000 m to 2,200 m. Encounter rates in shola forests fragmented by human interference were four times higher than those in natural shola forests. Most encounters of shortwings were near streams that were wet (running or damp). Emphasis is laid on the need for long-term studies to unravel the basic biology of the species in order to aid active conservation efforts. Introduction Five species of shortwings (genus Brachypteryx, subfamily Turdinae) exist; four of which are found in the Himalayas. The fifth, the endemic White-bellied Shortwing Brachypteryx major, is the only shortwing found in the Western Ghats, South India and has two subspecies: B. m. major and B. m. albiventris. It has been described as ‘‘a shy and retiring species, affecting deep shades, found singly or in pairs in the undergrowth, rarely above three metres’’ (Ali and Ripley 1987). It is known only poorly, with just 78 records from 1881 to 2000, inclusive of both sightings and collections (20 from Kerala and 58 from Tamilnadu). There are also 113 ringing records for four years between 1970 and 1991 (Appendix 1). Although it was reported to be fairly common by Ali and Ripley (1987), there are very few recent records and the species has been listed as Vulnerable (+2a,b,c,d,e; BirdLife International 2001). Of the various factors that may cause population decline, hunting and direct toxicological effects can be ruled out, as White-bellied Shortwing is neither a V. V. Robin and R. Sukumar 336 game bird nor one that is found in the proximity of industrialized areas. The most likely cause of the population decline of this species is habitat loss, fragmentation or degradation. BirdLife International (2001) states that the ‘‘species has a small, severely fragmented, declining range owing to destruction and fragmentation of its evergreen and semi-evergreen forest habitat’’. Before undertaking a detailed, long-term study to understand the biology and decline of the species, it was thought imperative to know its habitat preferences and abundance in different areas across the Western Ghats. This study therefore aimed to look at: (i) habitat preferences with reference to (a) altitude and (b) forest type; and (ii) abundance in different areas, with particular attention to areas of high local abundance, if any. The study covered the parts of the Western Ghats in Kerala and Tamilnadu as the first phase of a survey to cover the entire Western Ghats. Methods The study period consisted of four months of fieldwork, from 25 January to 20 May 2001. Areas with recent, frequent sightings of White-bellied Shortwing were identified from available literature and personal communications with various field biologists (Appendix 1). Two such areas, namely Rajamalai in Munnar, Kerala and Cairnhill Reserve forest in Ooty, Tamilnadu were visited to familiarize the authors with both subspecies of White-bellied Shortwing. For this purpose, observations were conducted from 05h00 to 18h00 every day (logistics permitting) for one week at each site. Once a bird was located and identified, it was followed for as long as possible. The calls were recorded (Sony WMD6C recorder with Sony microphone) and motion as well as still pictures were taken (Pentax SF7 camera with Zigma 300 mm zoom lens, Sharp video camera). Peak activity time was noted as the time when most shortwings were singing. The survey commenced only after obtaining confidence that the bird could be identified by sight or call without confusion. For the full surveys, several forest areas in Kerala and Tamilnadu were chosen, representing different habitats at different elevational gradients (Appendix 2). Trails inside forests were walked in the morning (07h00 to 12h00) and afternoon (14h00 to 18h00) while looking and listening for shortwings. The habitats sampled were categorized into tropical wet evergreen forest (evergreen forest), montane temperate forest (shola forest), tropical moist-deciduous forest, or plantations, based on Champion and Seth (1968). The montane temperate forests have been better described as montane evergreen forests (Mehr-Homji 1984, Shanker and Sukumar 1999) and are locally known as ‘‘shola forests’’ (hereafter referred to as shola forests). Altitude (using an altimeter) and habitat type were recorded every 0.5 km, and distance walked measured with a pedometer. Once a sighting (visual or audio) was made, the pedometer reading from the starting point was noted. Altitude and GPS location were also noted for every sighting (whenever possible). The bird was recorded by call only when it could be identified with confidence. While recording the number of individuals using just calls, only the number of individuals heard at the same time were recorded in order to avoid duplication or over counting. Many species of Turdinae are associated with streams and to quantify this for the shortwing, the distance to the nearest stream from the point of sighting was Status and habitat preference of White-bellied Shortwing Brachypteryx major 337 recorded. The stream, when present was classified into wet (running or damp) or dry. Data analysis Encounter rate (ER) was calculated as the number of individuals seen per km walked. The sightings were classified into three elevation classes: <1,000 m, 1,000–1,500 m and >1,500 m. The vegetation was categorized into four broad types: evergreen forest, moist-deciduous forest, shola forest and plantations. The three plantation types, pine, wattle and tea were pooled together as ‘‘plantations’’ for the analyses. Mann–Whitney U-tests were used to test for significant differences in encounter rates across various categories of elevation and vegetation. For applying the Mann–Whitney U-test, the data recorded for each category (elevation/vegetation type) were subdivided into sampling units of 0.5 km. To assess the proximity of streams to shortwing sightings, all sightings were classified under the following categories of distance to the nearest stream: (i) under 20 m , (ii) between 20 and 50 m and (iii) over 50 m. The null hypothesis of no difference between the categories was tested for every pair of categories using Chi-square tests. Preference for wet or dry streams was also examined using Chi-squared tests. All analyses were done using Statistica kernel release 5.5 and Microsoft Excel. Mapping The Survey of India maps of 1:100,000 were used as base maps. Areas with an elevation of 900 m and 1,500 m were generated from this. The forest cover in different areas was mapped based on Gaussen et al. (1961). MapInfo Professional version 5.0 and Arc View GIS version 3.0 were used for handling the maps. Results A total distance of 436.5 km was surveyed across the four broad habitat types: evergreen forest, moist-deciduous forest, shola forest and plantations, covering an elevational range of 60 m to 2,400 m. Four National Parks, seven Wildlife Sanctuaries, two Tiger Reserves and nine Forest Reserves were covered across Kerala and Tamilnadu during the study period (Appendix 2). A total of 214 sightings of the shortwing were obtained during the study. Vegetation types The sampling effort in different vegetation types was not equal as the focus was on covering as much forest as possible in different parts of the two states (Figure 1). Only 39 White-bellied Shortwing sightings (18% of the total) were in evergreen forests, even though the highest sampling effort was made here (307 km, or 70% of the total). Contrastingly, the maximum number of sightings (171, 79.5% of the total) were from 72.5 km (17%) of shola forests. Thus, sightings per unit effort were significantly higher in shola forests than in evergreen forests (Mann– Whitney U-test: n = 614, 145; Z = −17.91; P < 0.01). There were no sightings in V. V. Robin and R. Sukumar 338 0 50 100 150 200 250 300 350 Evergreen Forest Shola Forest Moist Deciduous Forest Plantations Distance Sampled (Km) Number of Sightings ER* = 0.13