@Someokapinextdoor: I have to agree in a way. However, I am still hopeful. I very much like the species mix in the Brehm building (I think it is more diverse and in my eyes also more attractive than any Tierpark building ever has been before). The monkey building also has become somewhat diverse as well even though there still mainly are mammals (but certainly more so than before). And the plans for the new elephant building also include birds and terrariums. Not to forget the giant aviary planned for the next development stage (if they get funds for this).
So in general you are quite right, but it's not all just downhill.
We shall see. I want to illustrate my point with a (albeit a bit polemic) example, mainly for people that aren't at Tierpark that often:
In my head I cheekily envision the old hierarchies at Tierpark as an eternal conflict between "deer dude" and "crane dude". Whenever there is space available, deer dude gets dibs on it, but if he doesn't have any new species crane dude can put a crane paddock there. This resulted in 18 deer enclosures and 8 crane encloures as of last year. But now it seems like crane dude is not there anymore (which is true, the bird curator retired) and the number of visible crane enclusures has halved in a few months (8->4) while the number of deer enclosures has only dropped by one (18->17). Of the 10 mammal species that were exclusively visible in the mountain area as of October, 6 have been brought down and are still visible (impressive on itself), whereas only 1 of 5 (?) bird species got this previlege. This points to my assumption that the mammal curator is still very powerful and interested in maintaining the collection whereas the birds don't have a powerful advocate right now.