Ecology of Rufous-Bellied Woodpecker Dendrocopos Hyperythrus in Himalayan Oak Forests G

FORKTAIL 34 (2018): 58–64 Ecology of Rufous-bellied Woodpecker Dendrocopos hyperythrus in Himalayan oak forests G. SHAHABUDDIN, T. MENON, R. CHANDA & R. GOSWAMI The Rufous-bellied Woodpecker Dendrocopos hyperythrus is the only known sapsucking species occurring in Asia, found in moist temperate broadleaved forests of the Western Himalaya, a forest type threatened by degradation and conversion to other land uses. We studied the habitat selection of the species using point counts over 210 survey-hours in four field seasons between 2016–2018. Field measurement of forest structural variables, analysis of landscape composition and observations on foraging behaviour were carried out to ascertain the reasons for its habitat choice. The species showed a significant preference for dense oak forest over other forest types and land-use. Its occupancy of forest sites was strongly dependent on canopy cover, and showed a weak association with tree girth and the proportion of dense forest in the surrounding landscape. It forages primarily in the mid-storey of the forest, on medium and large trees, mainly on their trunks. Sap-wells created by the woodpecker were seen on nine tree species, and it was seen foraging on seven others. Based on its unique sapsucking behaviour, habitat selection and narrow altitudinal range (1,500–2,700 m), we suggest that the species may be a useful indicator of high-quality oak forest in the Himalaya. Given the prevailing high threat levels to its habitat we urge a review of the IUCN conservation status of the species. INTRODUCTION In 2016, intensive surveys of moist temperate broadleaved forests between 1,700 and 2,400 m in the Western Himalaya yielded The Rufous-bellied Woodpecker Dendrocopos hyperythrus is a numerous sightings of Rufous-bellied Woodpecker (Shahabuddin et medium-sized woodpecker resident in the Himalaya of Pakistan, al. 2017). Such forests occur mainly between 1,500 and 3,000 m and India, Bhutan and Nepal and the hilly tracts of Bangladesh, are, in most places, dominated by oak species such as banj Quercus Myanmar, Thailand, south-east China and Vietnam, but with leucotrichophora, tilonj Q. floribunda and kharsu Q. semecarpifolia a migratory subspecies subrufinus breeding in Far East Russia (hereafter referred to as ‘oak forest’—see Singh & Singh 1987). and adjacent north-east China and wintering in southern China However, forest degradation and loss, caused by over-exploitation, (Winkler et al. 1995, del Hoyo & Collar 2014). Observations in warming, tourism activities, road-building and pine invasion, may South Asia indicate that it is a forest specialist largely restricted to threaten the species’s habitat (Pandit et al. 2007, authors’ pers. moist temperate broadleaved forest between 1,500 and 2,800 m obs.). Woodpecker species have been adversely affected by forest (Osmaston 1916, Grimmett et al. 1998, Dixit et al. 2016, eBird modification in European broadleaved forests (see Angelstam & 2018). Mikusinski 1994, Roberge et al. 2008, Stachura-Skierczynska et The Rufous-bellied Woodpecker is the only species of al. 2009). There is thus an urgent need for systematic studies of the ‘sapsucking’ woodpecker in Asia, feeding on sap from holes that ecology of the Rufous-bellied Woodpecker in the Western Himalaya, it drills in the cambium of trees (referred to as ‘sap-wells’). In this as it may be vulnerable to the effects of anthropogenic changes. respect, it is similar to the four species of Sphyrapicus sapsucker Our specific objectives were: (a) to study the habitat selection found in North America. The Rufous-bellied Woodpecker shows of the Rufous-bellied Woodpecker in the Western Himalaya; (b) to the anatomical adaptations for sapsucking, including a more slender study the role of forest vegetation structure in its habitat selection; pointed bill for drilling into cambium (relative to other woodpecker and (c) to explore its microhabitat preferences, with respect to tree species of its size) and brush-like tip to its tongue for licking tree species utilised, girth class, height of foraging and foraging substrate, sap (Osmaston 1916, Abdulali 1968, Zusi & Marshall 1970). in order to understand its dependence on its forest habitat. The species is listed as of Least Concern (BirdLife International 2018a), but it is believed that the overall population trend is adverse, with a decline in numbers probably caused by forest degradation METHODS and conversion, but there is currently sparse information to support such speculation. The species is little studied; early observations Study area were by Osmaston (1916) and Abdulali (1968), and the last field A 1,285 km2 study area, covering parts of the districts of Nainital observations were published from forests in Thailand by Zusi & and Almora in Uttarakhand state, India, was selected for intensive Marshall (1970). Distributional records from the Western Himalaya study within the oak forest biome lying between 29.30°N 79.36°E have been posted on eBird (eBird 2018) and in Dixit et al. (2016), and 29.54°N 79.84°E, in a region which forms part of an Endemic but there is no other data. A detailed study of this species, including Bird Area (BirdLife International 2018b). Temperatures can reach a its responses to forest degradation and conversion, its relationship low of 2.8°C in January and a high of 26.8°C in June and the average with forest structure, and foraging ecology, is long overdue. annual rainfall is about 1,500 mm (Climate-data.org 2018). The Sphyrapicus sapsucker species probably play a key role in Rufous-bellied Woodpecker shares this forest habitat with nine broadleaved forests because their sap-wells are available to other other primary cavity-nesters, the smallest being the Speckled Piculet avian and mammal species for foraging (e.g. Daily et al. 1993). Picumnus innominatus and the largest the Greater Yellownape It has also been found that the number of tree cavities created by Chrysophlegma flavinucha (Shahabuddin et al. 2017). The study sapsuckers is an order of magnitude greater than those made by area was chosen after ground surveys because there was adequate other woodpeckers, thereby increasing the nesting holes available representation of the six primary land-use types in this region: dense to secondary cavity-nesters (Daily et al. 1993). If this is true of oak forest, degraded oak forest, lopped forest (heavily degraded), the Rufous-bellied Woodpecker, it may well be an ecologically pine forest, built-up (tourist) sites and cultivation, between 1,700 important species in its Himalayan habitat and an umbrella species and 2,400 m. Dense oak forest, degraded and lopped oak forest are for forest conservation. well-documented, distinct categories of forest, created by different Forktail 34 (2018) Ecology of Rufous-bellied Woodpecker Dendrocopos hyperythrus in Himalayan oak forests 59 types of exploitation (see Thadani & Ashton 1995). Dense oak Data collection forests, which are largely protected from human use, have thick At each site the presence of Rufous-bellied Woodpecker was canopy cover, a preponderance of large and tall trees, dense epiphytes confirmed by two observers using the point count method. The and mosses and a dense understorey of shrubs and saplings. same pair of observers surveyed the sites throughout each field Degraded oak forest, created by light extraction for forest products season, thus eliminating observer bias. At each site the observers over long periods, tends to have thinner canopy cover, shorter scanned the forest vegetation within a radius of 30 m for 15 minutes. and younger trees, a poor understorey and largely lacks epiphytes. Since Rufous-bellied Woodpecker is a conspicuously coloured Lopped forest is heavily degraded and has almost no canopy owing species which forages actively (Plate 1), it was easily found if present to heavy extraction of fodder and fuelwood, but it possesses a dense in the area. Additionally, if calls were heard, an attempt was made shrub layer caused by tree-lopping for fodder. Cultivation consists of to locate the bird to confirm that it was within the circumscribed fruit orchards mixed with cereal and vegetable farming on terraces survey area. Surveys were repeated two or three times in each field created along hill slopes. Pine forest is largely dominated by chir season. Surveys started at 07h00 and continued until 10h00, to pine Pinus roxburghii with a few associates such as kaafal Myrica match the observed period of maximum bird activity in the forest. esculenta and rhododendron Rhododendron arboreum. Chir pine In summer 2016 and summer 2017 we carried out surveys in all is native to this region but has considerably expanded its range at six land-use types for Rufous-bellied Woodpecker; these surveys were the cost of oak forest, owing to the prevalent forest management repeated twice during each field season. No data were collected on practices—for example, frequent fires and intense use of oak forests vegetation structure or foraging behaviour. In both winter 2017 and lead to ‘invasion’ by chir pine, which regenerates well in drier soils summer 2018, surveys were repeated three times at the same 37 dense and relatively open tree canopy. oak forest and 37 degraded oak forest sites only and in addition data In the study landscape, 262 survey sites were selected within the were collected on vegetation structure and foraging behaviour. Data mosaic of forest, cultivation and human settlements. The number from each of the four field seasons were analysed separately. of sites was determined by the number that could be effectively To study foraging behaviour, the following notes were taken sampled in each field season by a single team of observers, as well as whenever the woodpecker was recorded: the tree species and DBH by the limited extent of remnant oak forests. Each survey site was (diameter at breast height in cm), the foraging height (metres) and the a point location having a homogeneous buffer of at least 50 m, and foraging substrate (main trunk, primary branch, secondary branch, was at least 200 m from the next nearest site.

Load more