The 3,146 panes of glass that have made up the ceiling and walls of the Tropical Rainforest exhibit since 1952 will be removed, recycled and replaced with special glass that allows more UV rays to enter the exhibit while preventing birds from flying into the glass. Seventy-five birds fly freely about in the Tropical Rainforest, the aviary’s oldest exhibit. Renovations will give them a 15-foot waterfall that spills into three tiers of ponds where birds can bathe, play and nest.