An investigation into the patterns of occupancy and detection of two endemic montane bird species, in Southern Western Ghats, India

Abstract

ABSTRACTMontecincla fairbanki(Palani Laughingthrush) andSholicola albiventris(White-bellied Sholakili) are avian species found only in a few high-altitude sky islands of the Southern Western Ghats. A taxonomic revision has resulted in the need for better resolution of species biology, especially their distribution, and factors affecting their distribution. The current study was an attempt to address this, by repeated surveys at plantation sites in the northern landscape of Idukki district (Kerala), and occupancy modelling. Around 96% of the sites surveyed were occupied byM. fairbankiand ∼52% byS. albiventris. Model-averaged site-averaged occupancy probability (ψ) ofM. fairbankiis 0.8618 (0.6659-0.9229), and ofS. albiventris, it is 0.4543 (0.1358-0.9972). Model-, site-, and survey-averaged detection probability (p) ofM. fairbankiis 0.6554 (0.5171-0.7341), and ofS. albiventris, it is 0.5731 (0.4102-0.7939). This confirms the hypothesis thatS. albiventrishas lower occupancy and detection probability compared toM. fairbanki. There is likely no effect on ψ of one species by the presence of the other, but there is likely a positive effect on p of one species, by the occupancy or detection of the other. Most significant effects on ψ ofM. fairbankiwere from the exclusive presence of dirt roads, elevation, slope, and visibility, and forS. albiventris, it was fromLantana camara, elevation, and understorey height. Most significant effects on p ofM. fairbankiwere from windy weather, sky conditions, time of surveys, and survey number, whereas forS. albiventris, they were from neutral weather, and survey number. Of the interactive effects hypothesized, significant evidence was found for the increase of ψ as a function of elevation, and the reduction of ψ in the presence of the invasiveL. camara(only forS. albiventris). The insights gained from this baseline study will be useful for further hypotheses testing and conservation efforts.