The interior of Horicon Marsh is home to a wide variety of marsh birds, from ducks and geese to pelicans, herons, egrets and cormorants. However, the scattered woodlands provide home to a great array of songbirds that can be found during the spring and fall migration as well as summer nesting populations. A close look may reveal a range of colorful songsters hiding among the dense foliage.
To some, the name Horicon Marsh has almost become synonymous with Canada geese. Each fall the largest migratory flock of Canada geese in the world migrates through Horicon Marsh with peak numbers reaching more than 200,000! The geese begin to arrive in mid-September, but for many the most popular time to see this fall spectacle is in mid-October as numbers approach the fall peak, other wildlife is still abundant, and fall colors paint a perfect background.
For those that enjoy wildlife, Horicon Marsh has long been known as one of the best places in the upper Midwest to see birds. While 300 different kinds of birds have been recorded at the marsh over the years, it is home to a number of threatened and endangered species and a lure for the occasional rare sighting.
Certainly birds are among the most visible forms of wildlife, yet other animals inhabit Horicon Marsh. Although many mammals come out at night, there is always the chance of seeing white-tailed deer in the uplands - or muskrats, mink and river otters as they swim through Horicon's shallow waters.
Wildlife comes in all shapes and sizes and the frogs, turtles and snakes are as much a part of a healthy wetland ecosystem as its birds and mammals. Painted turtles and snapping turtles are abundant at Horicon Marsh, as well as several different kinds of frogs. Only three species of common snakes live in the Horicon area and none of these are poisonous - in fact, most of them are rarely even seen, but play an important role in nature.