Bird surveys
Bird species that depend on aquatic production and occupy the riparian zone of Himalayan rivers were known from reconnaissance surveys and previous studies (Manel et al. 2000; Buckton & Ormerod 2002). For the current analysis, replicate surveys of the 68 reaches were undertaken in 2017-2018 in the pre-monsoon period (March-June), thereby capturing the breeding season of almost all the target birds. The banks were walked by the same observer (AS) during early morning (06.00 to ± 10.00) and late afternoon (15.00 to ± 18.00) following a previously established field design in which three visits were made to each river segment of 500 m length on different days (Buckton 1998). This visit frequency is considered appropriate for detecting river obligate species that occupy linear territories (D’Amico and Hemery 2003). The order of visits to each site within the basin were randomized as far as possible while ensuring minimum distances of 30-50 km between the sampling sites on consecutive days to maintain spatial independence (McCarthy et al. 2013). Species were recorded as present if they were observed during any of the three visits, while numbers of individuals of each species were recorded on every visit and eventually converted to mean numbers per visit. Bird species occurring in less than five river reaches were excluded from further analysis.