I just went to Willowbank yesterday and here is their (on show) bird list. It doesn't look as impressive written out in list form as it did in my head, but when you're actually at the park it seems like a good amount of species for the size of the place. I've put the number of males vs females if I know it (e.g. 2.4 means two males and four females), otherwise I've just put a single number (i.e. I would put 4 rather than 0.0.4 for the simple reason that while I don't know what sex those four birds might be, the staff at Willowbank probably do) and sometimes I've just had to put general wording such as "several" or "quite a few".
*Ostrich (one male, by the name of Bubbles!)
*North Island brown kiwi (I don't know how many birds there are as most of them are in outside breeding pens; there are quite a lot of them though)
*Great spotted kiwi (part of the Operation Nest Egg (ONE) programme so the number of eggs/chicks on site varies from zero upwards; however there is also one adult female off-display [there was a male which had come from Otorohanga to form a breeding pair but he died not long after arrival])
*Okarito brown kiwi (included in ONE as per above)
*Haast brown kiwi (included in ONE as per above)
*With regards to the ONE programme at Willowbank this article from January
Willowbank bursting with kiwis - news - the-press | Stuff.co.nz has a photo of a line-up of kiwi chicks there (showing Haast kiwi, little spotted kiwi, great spotted kiwi and Okarito kiwi). Very cool. In January of this year there were 60 kiwi of various species at the park.
*White heron (1)
*White-faced heron (3?)
*Black swan (2 that I think are part of the captive collection but they are common wild birds as well)
*Mute swan (3 I think)
*Domestic goose (a few)
*Cape Barren goose (several)
*Mallard (lots of wild, half-wild and captive ones in varying degrees of domestication!)
*Muscovy duck (seem to be quite a few, also muscovy X mallard hybrids)
*Carolina wood duck (a few)
*Mandarin duck (a few)
*Paradise duck (several)
*Brown teal (at least a couple of pairs. There used to be a pair in the Kiwi House years ago which was great as this species is nocturnal and they were very active in there. Now they are in an outside aviary and never seen)
*Campbell Island teal (at least one. Again, nocturnal. On my last three visits I've seen one in the aviary every time -- but never any on any previous visits!)
*Grey teal (wild ones)
*NZ scaup (wild ones)
*NZ falcon (0.1)
*Domestic turkey (lots)
*Helmeted (domestic) guineafowl (quite a few)
*Domestic fowl (lots and lots!)
*Blue peafowl (lots)
*Golden pheasant (at least 1.2)
*Silver pheasant (at least 1.1)
*Lady Amherst's pheasant (at least 1.1)
*Himalayan monal (1.2)
*Red-legged partridge (these used to be in the Alpine Aviary but I haven't seen any for a while)
*Japanese quail (several)
*Buff weka (several)
*Pukeko (these are everywhere! I expect they are all just free-loaders after the food hand-outs but at least some may be injured or hand-raised birds)
*Takahe (1.1)
*Domestic pigeon (dozens of domestic doves)
*Barbary dove (lots)
*Crested pigeon (quite a few)
*NZ pigeon (quite a few)
*Greater sulphur-crested cockatoo (one or two)
*Leadbeater's cockatoo (I think just one)
*Eastern rosella (several)
*Indian ringneck (lots in various colours)
*Blue and gold macaw (1.1)
*Kea (5 or 6 I think)
*South Island kaka (1.1)
*Yellow-crowned kakariki (several)
*Red-crowned kakariki (several)
*Little owl (at least 2)
*Morepork (at least 2)
*Sacred kingfisher (1)
*Rook (1)