Various observers have recorded more than 140 different species of birds at the ACUA Environmental Park throughout the seasons. Aside from nesting birds, numerous Neotropical migrant songbirds as well as birds of prey (also known as raptors) pause during migration to utilize ACUA woodlands and grasslands as ‘layover’ habitat. Layover habitat is critical to migrants for rest and nourishment along their hemispheric trek.
Grassland bird species thrive on the grassy slopes of the closed landfill cells. Birds such as Eastern Meadowlark, Horned Lark, and Killdeer are known to breed here during the spring and summer. Wintering grassland species such as Snow Bunting and American Pipit migrate to this location to spend a comparatively mild winter from their regular nesting habitat in the frigid Arctic. Two more grassland species, the Savannah and Grasshopper Sparrow, which are on New Jersey's threatened and endangered species list, have also been visitors to the landfill and are likely nesters as well.
A well-established trail of bluebird houses attracts cavity nesting birds annually, but not always the Eastern Bluebirds they were designed for. In alternating years Tree Swallows and House Wrens out-compete the bluebirds for this precious nesting resource. A few of the boxes placed along the nature trail in the Atlantic White-cedar bogs along Jarrett’s Run have been taken over by Red Squirrels.
Red and Gray Squirrels, Raccoons, Opossums, Chipmunks, Red Fox and White-tailed Deer are some of the mammals found in the park. Numerous reptiles and amphibians also inhabit the park. One of the first true indicators of spring is the high piping sound of the abundant Spring Peeper, a tiny native frog. Other species of frogs and toads along with various snakes and turtles, including Snapping and Painted Turtles are found in low lying and wetland areas of the environmental park.
Several wood duck nesting boxes are also installed to help provide a habitat for these cavity nesting animals.