Foraging niche differentiation among sympatric woodpecker species in forests of north-western India

The sub-Himalayan dipterocarp forests of subtropical region in northwest India support 17 species of woodpecker. From a conservation perspective it is necessary to assess the ecological requirements of woodpeckers in these biologically diverse landscapes, which are experiencing habitat modification and decline in some woodpeckers. We studied the foraging niche differentiation among ten sympatric woodpeckers in the sub-Himalayan forests of northwest India: Dendrocopos canicapillus, D. macei, Picus cldorolophus, P. xanthopygaeus, P. can us, Dinopium shorii, D. benghalense, Chrysophlegma [Picus] flavinucha, Chrysocolaptes lucidus, and Mulleripicus pulverulentus. We examined the foraging site preferences of individual woodpecker species and explored the role of inter-specific differences in foraging behaviour as a possible mechanism for their coexistence. Observations on foraging woodpeckers were taken vis-a-vis the following niche dimensions: diameter of the foraging tree, height of the foraging bird, type of substrate on which it was foraging, vertical position with respect to canopy, condition of the forage tree and condition of the substrate. Distinct preferences were evident among species in their foraging tree diameters, foraging heights, vertical positions, and choice of substrate type, while preference for dead substrates was not an important distinguishing factor. Species that overlapped in one dimension generally segregated along other dimensions. Niche segregation in forage tree diameter was associated with body weight. Based on their overall niche overlaps species could broadly be differentiated into groups according to body size viz. small (3 species), medium (3 species), large (3 species), and very large (1 species). Our study demonstrates that differentiation in foraging may be a likely mechanism for coexistence of sympatric woodpeckers in this region. Given that larger species prefer larger substrates, removal of mature trees could affect their abundance, and homogenisation of stand structure could lead to impoverishment of woodpecker diversity.