Terry,
Welcome back from foreign lands......and thanks for your interesting account of your rainforest/jungle birdwatching trip to Borneo which, as you say, with 160 species including 52 lifers towards the end of the rainy season, represents a very good result.
I know that you have done many such trips but what a lot of people who haven't done any/much birding in those surroundings don't realise (and TV programmes don't always help) is that the deeper you go into the jungle/rainforest the less likelihood there usually is of sighting very many typically skulking birds, especially in the absence of any fruiting trees and clearings....and the slippery paths can become just used narrow animal tracks going nowhere.
The best birdwatching can often be on the fringes, around villages, in cultivated areas, clearings and where the secondary growth exists with more light. As you mention, birding in the rainforest/jungle itself is about the most difficult type of birding to do, especially alone, plus temperatures of 30+ degrees and extremely high humidity. After all, the emergent layer and the canopy layer are out of sight, the understorey layer often disappointing and the forest floor receives little if any real light.
When I lived in Singapore in the early 1960s ( when I was only in my early 30s, and it was still some years before the first UK birdtour company (Ornitholidays) was established) the best results on 'local' birding trips to North Borneo (Sabah), Sarawak and especially to 'Malaya' itself across the Johore Causeway were always in the paddy-fields, around the villages and in the secondary jungle. The week-long, real Army 'jungle training' exercises we did annually, where we were always accompanied by trackers and a protective team of Gurkhas, were quite boring wildlife-wise once we entered the real jungle itself.
I remember one birding trip early on in my 3-year tour when I had parked up near a Malay village and then penetrated alone (plus compass, etc.) into deeper jungle, I saw very little for a couple of hours or so (although I heard 'things') .......and then I heard what I initially thought (at last) might be the sound of a flock of birds ahead..........dream on, it was a crowd of spectators cheering on a bicycle race ; I had penetrated through to the outskirts of a large settlement.
I'm sure you avoided that sort of experience in Borneo, Terry.
Freddy