Here is my review (from 2012) of the South Building and adjacent aviary:
MARSH PAVILION:
River Otters – A single young otter had a large pool all to itself and there are massive viewing windows and carpeted, tiered seating that comes in handy after the 3-block walk from the Bay & Ocean Pavilion to the Marsh Pavilion. Near to the otter habitat are a series of stuffed mammals in cases, a Native American Exhibits section, and a Bird Exhibits area with taxidermy specimens and a diorama of a Decoy Carving shop.
Walk-Through Aviary – This is a half-acre habitat that has a wooden boardwalk that winds through a heavily shaded area. Cattle egrets were out in droves but it was difficult to spot many other birds in what seemed like a large, half-empty aviary. A woodpecker had a cage to itself, as did a great horned owl, but overall this aviary has a lot of unfulfilled potential. Apparently there are over 70 birds of 30 different species (according to the aquarium’s website) but I saw probably 20 egrets so I’m not confident in those quoted numbers.
Marsh Exhibits – The rest of this pavilion is filled with exhibits for smaller creatures, and the list of species includes: blue crab, Atlantic silverside, striped killifish, mummichog (those 4 all in one exhibit); skilletfish, feather blenny and striped blenny together; lined seahorse, northern pipefish, oyster toadfish, common snapping turtle, northern water snake, northern diamondback terrapin, red-jointed fiddler crab, sand fiddler crab, mud fiddler crab and horseshoe crab.
Many of the Marsh exhibits are typical terrariums that are found in many zoos and aquariums, and additional species that I saw include: green treefrog, barking treefrog, gray treefrog, squirrel treefrog and fowler’s toad all together in a tall exhibit; copperhead snake, eastern cottonmouth, canebrake rattlesnake, broad-headed skink, five-lined skink, hispid cotton rat, eastern garter snake, eastern rat snake and eastern box turtle. There is a Macro-Marsh area that features giant-sized marsh inhabitants that primarily appeal to children, and a desk with all types of skeletons and bones on it for visitors to touch.