You'd have to ask @alexkant about the circumstances of this photo being taken, as it is his, but I believe it is several years old and was taken offshow.
I imagine it will be somewhere in the low hundreds, given the following information on the IUCN page regarding the 2011 population:
In 2011, the captive population stood at 94 individuals (49 at the Keauhou Bird Conservation Center, 44 at the Maui Bird Conservation Center, and 1 at the San Diego Zoo), including 39 birds used as breeders (Switzer 2011).