The former status of the white shouldered ibis Pseudibis davisoni on the Barito and Teweh Rivers, Indonesian Borneo.

Analysing historic species ranges is important for assessing the population trend and conservation status of threatened species. Understanding the spatial variation in threats to these species requires an analysis of regional differences in historic and current status, and the underlying causes of their decline. Historic literature can help in this process. Here we provide a translation of field notes by Salomon Muller during his 1836 travels in SE Kalimantan. We focus on the notes regarding White-shouldered Ibis Pseudibis davisoni (Hume, 1875), one of Southeast Asia's most critically endangered birds. Indonesian records for this species from the few last decades are mostly restricted to the Mahakam River in East Kalimantan, Indonesian Borneo. Muller recorded the species almost daily along the middle reaches of the Barito River in Central Kalimantan, and provided details on its food and morphology. Muller's data suggest that in the 19(th) century a healthy population of White-shouldered Ibis was present along the Barito River. We speculate on the connection of this population with the Mahakam one and the cause of its apparent extinction.