Ecology of Rufous-bellied Woodpecker Dendrocopos hyperythrus in Himalayan oak forests

The Rufous-bellied Woodpecker Dendrocopos hyperythrus is a medium-sized woodpecker resident in the Himalaya of Pakistan, India, Bhutan and Nepal and the hilly tracts of Bangladesh, Myanmar, Thailand, south-east China and Vietnam, but with a migratory subspecies subrufinus breeding in Far East Russia and adjacent north-east China and wintering in southern China (Winkler et al. 1995, del Hoyo & Collar 2014). Observations in South Asia indicate that it is a forest specialist largely restricted to moist temperate broadleaved forest between 1,500 and 2,800 m (Osmaston 1916, Grimmett et al. 1998, Dixit et al. 2016, eBird 2018). The Rufous-bellied Woodpecker is the only species of ‘sapsucking’ woodpecker in Asia, feeding on sap from holes that it drills in the cambium of trees (referred to as ‘sap-wells’). In this respect, it is similar to the four species of Sphyrapicus sapsucker found in North America. The Rufous-bellied Woodpecker shows the anatomical adaptations for sapsucking, including a more slender pointed bill for drilling into cambium (relative to other woodpecker species of its size) and brush-like tip to its tongue for licking tree sap (Osmaston 1916, Abdulali 1968, Zusi & Marshall 1970). 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 and conversion, but there is currently sparse information to support such speculation. The species is little studied; early observations were by Osmaston (1916) and Abdulali (1968), and the last field observations were published from forests in Thailand by Zusi & Marshall (1970). Distributional records from the Western Himalaya have been posted on eBird (eBird 2018) and in Dixit et al. (2016), but there is no other data. A detailed study of this species, including its responses to forest degradation and conversion, its relationship with forest structure, and foraging ecology, is long overdue. Sphyrapicus sapsucker species probably play a key role in broadleaved forests because their sap-wells are available to other avian and mammal species for foraging (e.g. Daily et al. 1993). It has also been found that the number of tree cavities created by sapsuckers is an order of magnitude greater than those made by other woodpeckers, thereby increasing the nesting holes available to secondary cavity-nesters (Daily et al. 1993). If this is true of the Rufous-bellied Woodpecker, it may well be an ecologically important species in its Himalayan habitat and an umbrella species for forest conservation. In 2016, intensive surveys of moist temperate broadleaved forests between 1,700 and 2,400 m in the Western Himalaya yielded numerous sightings of Rufous-bellied Woodpecker (Shahabuddin et al. 2017). Such forests occur mainly between 1,500 and 3,000 m and are, in most places, dominated by oak species such as banj Quercus leucotrichophora, tilonj Q. floribunda and kharsu Q. semecarpifolia (hereafter referred to as ‘oak forest’—see Singh & Singh 1987). However, forest degradation and loss, caused by over-exploitation, warming, tourism activities, road-building and pine invasion, may threaten the species’s habitat (Pandit et al. 2007, authors’ pers. obs.). Woodpecker species have been adversely affected by forest modification in European broadleaved forests (see Angelstam & Mikusinski 1994, Roberge et al. 2008, Stachura-Skierczynska et al. 2009). There is thus an urgent need for systematic studies of the ecology of the Rufous-bellied Woodpecker in the Western Himalaya, as it may be vulnerable to the effects of anthropogenic changes. Our specific objectives were: (a) to study the habitat selection of the Rufous-bellied Woodpecker in the Western Himalaya; (b) to study the role of forest vegetation structure in its habitat selection; and (c) to explore its microhabitat preferences, with respect to tree species utilised, girth class, height of foraging and foraging substrate, in order to understand its dependence on its forest habitat.