Spring peeper balances between a dried brown leaf and green blade of grass
Spring Peeper: The tiny bodies of spring peeper males project a voice much larger than would seem possible. © Derek Johnson

Stories in Wisconsin

Wisconsin Nature Notes

In April, spring has sprung in Wisconsin and nature is waking up!


One of the most awaited harbingers of spring is the mid-April emergence of spring peepers and wood frogs. For the nearly six months of winter, these frogs were hibernating in the forest duff, literally frozen, but now the sudden pandemonium of their calls from their woodland ponds says the frost has left the soil and they have survived another northern winter. The tumult of the males’ calls can be deafening, their exuberance in the still chilly April evenings announcing the defining end of winter. The males call once every second, their tiny one-inch-long bodies projecting a voice much larger than would seem possible.

The Conservancy’s Catherine Wolter Wilderness Area with its 36,000 feet of undeveloped shoreline on 15 wild lakes, and its many associated woodland ponds, is prime habitat for frog chorusing. Numerous looped hiking trails can be walked in the early evening to hear their music and to come away amazed at the life force of frogs.

Loon on water rises up and spreads wings
Common Loon: When these beautiful birds return to Wisconsin in spring, the fight for territory begins! © Steve S. Meyer


Lakes in Wisconsin’s Northwoods average 148 days of ice-cover, so when the ice finally goes off in late April, the return of open water is greeted joyously! There’s an icing on this cake, too – common loons almost always return within 24 hours of the ice’s departure, having bided their time mostly on the open water of the Wisconsin River. People watch intently for the loons to arrive, hoping that “their” loon pair will grace their lake for another year. Loon competition for prime lake real estate is so intense that a lake can be only partially open and the loons will land.

Once they’ve returned, territorial fights occur regularly between adult loons. Most loons acquire their territories by force, a non-breeding adult intruding onto a lake and battling with its pair member to evict him or her. Loons symbolize wildness to most northerners, and these battles can be both wild and sometimes fatal.

Common loons nest on The Nature Conservancy’s 971-acre Guido Rahr, Sr. Tenderfoot Forest Reserve. With its four miles of undeveloped shoreline on Tenderfoot, Roach, and Mirror lakes, loons find exceptional habitat for breeding and nesting. Visitors who take the time to paddle to the site are often rewarded with close observations of one of the Northwood’s most beautiful birds.

Aerial view of intensely blue Mississippi River waters winding their way among many intensely green backwater islands
Upper Mississippi River: The river is an important stopover for canvasbacks, lesser scaup, common goldeneye, ring-necked ducks and other birds during migration. © Robert Hurt


There are few better indicators of spring’s return than the arrival of migrating birds, and among the earliest returning migrants are ducks and other waterfowl. The Mississippi River is an important stopover for these birds on their way to their prairie pothole nesting grounds in the Dakotas and adjacent Canadian provinces. They can be easily seen from river overlooks at the Upper Mississippi River National Wildlife and Fish Refuge in Wisconsin.

The refuge attracts many kinds of waterfowl and is known for its concentrations of canvasback ducks. Thousands of these birds can be found along the river in the early spring. Canvasbacks are diving ducks with large feet positioned far back on their body to propel their trips underwater where they feed on wild celery tubers on the river bottom. Other ducks that can be seen include lesser scaup (also called bluebills), common goldeneye and ring-necked ducks. Watch for bald eagles that occasionally fly low over groups of ducks, spooking the birds to see which are weak flyers and potentially easy prey.

A good location to watch ducks is the refuge’s Shady Maple overlook five miles south of La Crosse off Highway 35. It is one of the first places with open water in spring that attracts ducks. Return in the fall to see even more birds – hundreds of thousands of ducks gather on the refuge during migration in late October.

The Nature Conservancy is working with many partners to protect and restore the health of the Mississippi River basin for millions of migrating birds and for all of us who depend on it for drinking water, food, power, recreation and transportation.


On the other side of Wisconsin, another early spring migration takes place not on but underwater. On the western side of Green Bay, northern pike – large predatory fish that can exceed four feet in length – leave the bay and ascend streams to spawn as soon as the ice is out.

The pike swim up streams, creeks, even roadside ditches, eventually arriving in shallow waters that barely cover their backs. They spawn in the remains of last year’s emergent vegetation where newly-hatched fry can hide until large enough to make the return trip to the bay in late May. Research has shown that pike will ascend a variety of waterways during their lifetime to spawn. Unlike salmon, they do not return only to the streams where they were born.

A good place to see pike performing this ancient spring ritual is along the north side of Lineville Road, not far from the Barkhausen Waterfowl Preserve, approximately five miles north of downtown Green Bay. There you can sometimes see pike spawning in as little as four inches of water in the roadside ditch.

Not all of the rivers and streams draining to Green Bay are accessible or navigable to spawning northern pike. If they are crossed by a road, fish must swim through a culvert to continue their travels. If the drop at the outlet of a culvert is too great, northern pike can’t jump up into it. If the water velocity is too fast, fish may tire before they make it through the culvert and get washed back out. Too little water in the culvert, and fish can’t swim through.

The Nature Conservancy has identified culverts that are barriers to migrating pike. We are helping engineers design culverts that are both fish-friendly and sized appropriately to the amount of water flowing through them to help ensure that there will always be pike in Green Bay and the Great Lakes.

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