They do it some, what I'm saying is it'd be beneficial for them to do it more often, as there are many programs that remain struggling in the AZA but could be much more successful with additional help from unaccredited places.
I used these examples since they are extremely common in zoos, while other species (that are also threatened, might I had), are in need of additional holders. If five or six zoos switched from the two callicthrid species in question to a different species, say Pied Tamarins or Golden-headed Lion Tamarins, the AZA would be able to successfully manage more than two callicthrid species, whereas right now only two are designated as having sustainable populations. I'm not advocating for phasing out these species, just a slight "phase down" to reallocate some space to other struggling programs. African Penguins have been covered extensively on other threads, and the basic point remains the same as with callichtrids- a slight phase down in favor of other Spheniscus species would not be detrimental to the African Penguin SSP, which can be sustainable with less than the 1,000 Penguins currently in the SSP.
The point about encouraging zoos to switch towards more threatened species was especially in regards to waterfowl, where many SSPs are in need of more holders despite three unmanaged, common species having sizeable populations in the AZA. When an exhibit is not zoogeographic, there's no good reason for a zoo having Ringed Teals in an aviary instead of a more threatened, managed waterfowl species (e.g. Madagascar Teal). This could also apply to other places where a least concern species is taking up significant space when there is a more endangered species with similar care requirements that are struggling for others (e.g. both Sloth and Andean bear SSPs are struggling due to lack of holders, and could benefit from a few zoos switching to an SSP species from American Black Bears).
