This document presents long-term personal field observations of Bornean Bristlehead (Pityriasis gymnocephala), with particular attention to the potential impacts of playback disturbance on group structure and behaviour in this highly social species. The observations suggest that playback may contribute to sustained changes in group cohesion and site use. This documentation is intended to serve as a useful reference for future observers, researchers, and conservation practitioners, and to support more informed and responsible approaches to studying this rare species in the wild.