I don’t have a credible source, beyond my involvement with the species in the private trade.
In terms of zoo populations, it’s definitely violet, red crested, white cheeked, great blue, and lady Ross by a fairly significant portion. All other represented species likely number under 10-15 individuals for the most part.
In private hands, however, it’s a bit of a different story. White Cheeked, Red Crested, and Guinea are by far the most common. Violet is fairly well established, but has seen a slight decline in breeding in recent years. They’re likely the most genetically diverse population, however. Lady Ross is present, but numbers aren’t stellar and the majority of production occurs from one breeder. Livingstone’s have likely outnumbered lady Ross in population over the past year or two thanks to several different people having success with the species, and are demographically strong; but genetics are poor, the founder population is effectively 5-6 birds at best. Great Blue are slowly gaining in numbers, but it’s limited primarily to one breeder and the founder base is small, but mainly wild caught birds. Another fun fact about the blue turaco is that I’m set to potentially become the first holder of them in Canada, if things everything goes according to plan. Nothing is set in stone yet, but my hopes are high about this one!
The white crested population has been stagnating over the past several years, although there has been a small surge of breeding success over the past year. However the population is demographically poor, with the majority of birds being very old, and it’s also quite inbred at this point.
Western gray plantain eaters are still present in the hobby as they were imported in very large numbers over over the past 10 years, however breeding success has been very, very poor with them, and unless there’s a concentrated effort to breed and secure the population, it will likely be all but vanished within the next 10 to 15 years.
Fischers are around and gradually growing a number, but the founding population is small, and same thing, only one breeder in the private hobby is really working with them. However they’ve been having enough success that they’ve finally been able to start distributing birds to other breers, so this small population will likely do well and grow as long as it is managed effectively.
Purple crested are functionally extinct. I’m only aware of two individual birds in private hands, an upper middle aged female in Florida, and a very old male held in… I think California? Plus a male at San Antonio zoo, and an individual at discovery Cove.
White belly go away birds are struggling but have the potential to make a come back. None in private hands, but San Diego and Houston still hold the species.
There might be one or two individuals of other species still living in the states (knysna, black billed, hartlaubs), but if there are, they are very, very old birds, and are essentially living relics from populations have long since become non-viable.