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.