Back in 2013, we were informed by a park ranger at nearby Raccoon Creek State Park that this bridge sits smack in the middle of a gigantic Great Blue Heron rookery. For several weeks in the March-April time frame, thousands of herons descent on this place to have their children. He said the fact that people driving over this bridge would disturb the birds (rookeries of this size are very rare) was one of the main reasons that the bridge was closed. For what it's worth, when I walked over it in 2013, the deck was in much better condition than that shown in earlier pictures.
Pictures posted