Demographic changes of a tropical understory bird in naturally patchy montane habitats in southern India

Abstract

ABSTRACTThe occurrence, density and survival of a species often depend on various aspects of the habitat that it occupies including patch size and disturbance. The demography of most threatened tropical species largely remain unstudied but could provide valuable information about their biology and insights for their conservation. Our study examined the effect of patch size and disturbance on different demographic parameters of an understory, threatened, endemic bird, the white-bellied shortwing in the tropical biodiversity hotspot of the Western Ghats in India. We sampled eight plots on a sky-island using mist-nets for four years in a ‘Robust design’ mark-recapture framework. Based on model selection using AIC values, the model with survival as a function of disturbance fits the data better than models with abundance or with these parameters modeled as functions of forest patch size. Shortwing density and sex ratio were not different across forest patch sizes or differing disturbance regimes. However, the survival rate of the species significantly decreased with increasing disturbance but was not related to forest patch size. Our study is possibly the first to provide critical baseline information on the demography of a tropical understory species from this region.