For walk-through aviaries I prefer laminated guides like this (rather than static signs employed at many zoo walk-throughs) that you can pick up at the entrance and deposit into a holder at the exit, because inevitably you tend to encounter a mystery bird when you are someway from the identi-board. Probably a few "disappear" as visitors retain them as souvenirs, but they're cheap enough to replace as long as the images are stored on the office computer, and cheap to laminate. Shame all the birds on this one are commonplace species though.
