Visitors to the well-known Borneo Rainforest Lodge would have seen this bird on the (Danum) river as seen from the restaurant.  I have also seen the Great-billed Heron Ardea sumatrana along the river at the Tabin Wildlife Reserve.  It is also reported along the coast but so far I have only seen it along  the two rivers mentioned.  A graceful flyer, it is usually seen alone.  Easily the largest heron in Borneo.