I haven't seen the motmot, the Madagascar turtle doves or the quelea recently. It has been longer since I saw the yellow-streaked lories and the pheasants and I don't recall ever seeing the bulbul or the quail.I suspect that the motmot and the quelea were old birds which may have passed away, I think that many of the others are off-show, but I don't know any specifics.
There has been some shuffling of the bird collection in the past few months, there are still one or two empty aviaries and the labels are not 100% trustworthy - but I tried to keep your list in mind as I visited today, to supplement the information provided in previous posts.
The crested quail doves (or mountain witch doves as I prefer to call them) are in Reptile Tropics and I saw a green turaco there today too (there is also a chick in the rearing room of the Avian Breeding Centre). The pair of liocichlas are in the lobby area between Reptile Tropics and the Desert House, which has recently been renovated. I didn't see the grey-backed thrushes today, but a few weeks ago they were in one of the separate aviaries at the back of this lobby which are hard to see from the footpath - you might be able to spot them, but a camera with a long lens or a small pair of binoculars would help.
I did see one of the Duivenbode's lories, but their aviary is large and thickly planted and I suspect they spend a lot of time in their nest box, so it is much easier to hear them than to see them. You won't have any problem seeing the speckled pigeons in the Brookside aviary, they are the only birds in there at the moment, except for the African eagle owl!
The labelling in the Amphibian Ark is also dodgy. There are some nice new exhibits without labels, and perhaps some don't have amphibian inhabitants yet, there are some blank windows waiting for new exhibits too, but there are some nice dart frogs and mantellas too. You should be able to see the whole zoo in 4 hours, provided you walk at Pertinax pace. If you need to save time you could miss the path past the cheetahs, they aren't particularly easy to see and there is nothing else beside that path. Finally, don't wouldn't wait until 4pm to look for the echidna. Try earlier, but be prepared to revisit, he's worth it