Introduction
Species distribution modelling (SDM) are widely used methodology that has been used to predict the distribution of species on any geographical range (Beale and Lennon, 2012). These are also known as bioclimatic models envelope models and ecological niche models (Araújo and Peterson, 2012). The Maximum Entropy (MaxEnt) model predicts the potential habitat considering entropy of different variables associated with present location of species (Singh et al., 2020). SDM is one of the most active areas of global ecology and many papers has been published around the world to date (Booth, 2018). These are models that use species environment relationships to explain and predict distributions of species(Hao et al., 2019). They rely on statistical correlations between existing species distributions and environmental variable (Li and wang, 2013).
Hornbills are recognized as one of the most important bird species in the tropical and subtropical forest of Asia and Africa (Sun et al., 2019). Hornbills are large birds belonging to the Bucerotidae family and out of the 59 extant species of hornbills, 31 are found in Asia(Franco and Minggu, 2019). Hornbills are often called as “Farmers of the forest in terms of their habitat, food, nest-site and seed dispersers (Sherub and Tshering, 2019). They are known as good indicators of the health of forests(Sherub and Singh, 2020). The unique breeding biology of these birds means that they are dependent on big trees of primary forest(Ouithavon et al., 2005).
Hornbills are distributed throughout forested areas of the country (Chaisuriyanun et al., 2011). Bhutan provides a safe home for four hornbill species; Wreathed hornbill Aceros undulates , Oriental Pied hornbill Anthracoceros albirostris , Rufous-necked hornbillAceros nipalensis, and Great Hornbill Buceros bicornis(Nepal, 2020). Asian hornbills are hunted for their body parts (Casque and tail feathers for traditional attire), for the consumption of their meat, and for their body fat, which is believed to have medicinal properties(Aiyadurai et al., 2010;Bennett et al., 1997). Its population is declining in an alarming rate due to continue habitat fragmentation and degradation, deforestation, logging, and increase in hunting pressure (Pawar et al., 2021). Today only a third of their natural habitat remains a large proportion of it in a fragmented state and with extraordinarily high levels of threats to their persistence (Laurance, 1999) . The target species Rufous-necked hornbill has been reported to be extinct in Nepal and close to extinction in Vietnam(Poonswad et al., 2013)(Shukla et al., 2016). To date, no study has been carried out to know regarding hornbill’s habitat suitability and distribution in Bhutan. Against backdrop, this study is intended to fill the existing gap with the objective to delineate the potential habitat suitability and identify critical variables associated with Rufous-necked hornbill and Great hornbill in Bhutan.