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For information about Horicon Marsh, contact:
Horicon Marsh Wildlife Area
N7725 Hwy 28
Horicon WI 53032

Wildlife of Horicon Marsh

Shoveler photo courtesy of Jack Bartholmai

It is commonly asked when the peak of migration is at Horicon Marsh. Of course, that depends on which group or species of birds we are talking about. The best migration time to see the greatest variety of birds is from mid-April to mid-May and mid-September through October. However, there is no one time when you can see all the birds of the marsh. By the time one group of birds is at its peak, others may have already departed or might not yet have even arrived. Therefore, to see the greatest variety of birds it requires several trips throughout the season and throughout the year in order to get a true feel for the diversity and abundance of wildlife that is attracted to and supported by Horicon Marsh.

Over the years, approximately 300 species of birds have been sighted at Horicon Marsh. Among them are many common wetland and upland birds and some of Wisconsin's rarest bird sightings. On a single day in spring it is not unusual to find up to 100 species of birds on Horicon Marsh alone!

Each year a great number and variety of birds return to Horicon Marsh. This, in turn, attracts a great number of bird watchers who come to discover, observe, and learn about our birds. Each year the same sequence of bird migration takes place. The birds return to our state in the same order, but the exact date depends on the progress of spring. Between warm and early spring seasons and late seasons, birds may be as much as 3 weeks apart from year to year.

 Each group of birds, however, responds to a particular environmental condition which encourages them on their way. The geese arrive when the snow begins to melt and ducks cannot advance farther than the melting of ice and availability of open water. Woodcocks have to wait until frost is out of the ground so that their food of worms and insect grubs becomes available. Most songbirds have to wait until the weather is warm enough to assure a steady supply of insects. Therefore, the annual progress of spring determines the progression of the spring migration.

Horicon's phenology of birds


While the marsh may be covered in ice and snow, it is not devoid of bird life during the depths of winter. Common winter birds of the marsh include northern harrier, red-tailed and rough-legged hawks, snowy owls (occasional), lapland longspur, snow bunting and horned larks. Canada geese commonly overwinter on the marsh, but depart when deep snow covers the remaining food supply.

During the midst of winter bird populations remain rather stable as they settle in for the season. Winter bird surveys indicate that about 35 to 40 species of birds can be found even at this time of the year through careful watching.


By the middle of the month, Wisconsin's first "spring" migrant, the horned lark, returns in bigger numbers. Although some remain throughout the winter, they become more abundant in the fields and along the roadsides surrounding the marsh. Canada geese usually return by late February or early March depending on when the snow melts, making food available.

The first signs of spring are indicated by the arrival of horned larks, red-winged blackbirds, grackles and Canada geese - the cycle begins anew. Depending on the season, by mid to late February or early Marsh, the thawing snow signals the beginning of the seasons all over again.


Great Blue Heron

Red-winged blackbirds and grackles return following the geese, with the first sandhill cranes returning before the middle of the month. The first arriving robins, song sparrows and killdeer return by mid-March. Mid to late March is usually the time when the ducks begin to show up on the first open water. They are followed by coots and pied-billed grebes. As water birds, they cannot advance their migration until the ice melts. Early arriving birds concentrate on the area rivers since the moving water will be the first to break the ice. As the shallow wetlands and finally the lakes open up the large flocks of ducks become more common.

Great blue herons will often be seen in early to mid-March, but the majority of the birds tend to wait until nearly the end of the month before they return to their rookery at Fourmile and Cotton Islands. Once settled in they can be seen throughout the day, from April to the end of summer, in the air over Horicon Marsh and the surrounding land. Great egrets stay back for another 2 to 3 weeks, with the majority of the birds arriving in early to mid April.


Geese Flying

From mid April through the end of May is the peak of activity for most spring migrating birds. With the disappearance of the ice and the warming temperatures, a great variety of birds come streaming into Horicon Marsh. Snipe can be heard over the marsh, while rails, swamp sparrows, yellow-headed blackbirds, black-crowned night herons and many others can be seen on the marsh or heard calling from the stands of cattails. This is also the time when bald eagles, osprey and peregrine falcons are most commonly seen at the marsh.

By the third week of the month the great flocks of Canada geese depart Wisconsin for their northerly nesting grounds along the shores of James and Hudson Bay. Some geese will be seen on the marsh throughout the summer. These are the giant Canada geese, which is a separate subspecies that nests in Wisconsin and other sites across the mid-west.

The northerly nesting ducks depart soon after the geese. Local nesting birds are to be seen courting on the marsh just prior to nesting. Once nesting begins in May, waterfowl are less often seen at Horicon Marsh, as the females are on the nest and the males form small flocks in the marsh.

April is also the time when the shorebirds return. When water levels are low enough to form mudflats, populations can be very abundant at the marsh. They will often remain until the middle of May. During April is also when the first big waves of songbirds come through the area. The tree swallows will be seen over the marsh early in the month with the other species returning about 3 weeks later. The first of the warblers, the yellow-rumped, returns in early to mid-April, while the palm, black-throated green, black and white warblers will be seen by late April. They will be followed by the big migratory waves and great variety of other warbler species in the second and third week of May.


After the northern nesting waterfowl have departed the marsh the great flocks of songbirds begin to reach the peak of their migration. From late April to the third week of May is the best time to watch and listen for the spring songbirds.

The best time to see them is prior to the full development of the leaves of our forest trees. Since many of these birds will be perched in the tree tops and among dense shrubs, they are more readily seen when the trees and bushes are still rather bare. In some years the leaves may develop before most of the birds even arrive making for a real challenge. In these years of warm spring weather it is an extra challenge to find the birds. The best method is to identify them by song rather than sight, but that requires training, experience and a good ear for bird songs.

Among the great variety of songbirds to be seen at Horicon and many other sites are tanagers, orioles, rose-breasted grosbeaks, vireos and flycatchers. These are known as the passerines [perching birds or songbirds]. Among them are many of the neotropical migrants. These are birds that winter in the tropical rainforests and nest in the forests and grasslands of Wisconsin, surrounding states and Canada.

As May arrives the remainder of our spring birds return. In the marsh, this includes the green heron, least bittern, marsh wren and many others. This is also the time when some of our rarest birds can be sighted here. Horicon Marsh is one place where unusual wetland birds may be commonly sighted. These include little blue herons, snowy egrets, glossy and white-faced ibis and even white pelicans.

June, July, August

Wood Duck Brood

Summer is the nesting season for birds. Nearly half of the birds known to the marsh remain here to rear their young. While many birds are still nesting the fall migration is beginning for others.

By late July the yellow warblers are already departing for their tropical wintering areas. By August, the first of the shorebirds, sandpipers and plovers, are arriving from their arctic breeding grounds.


This is the beginning of the fall migration for most birds. Shorebirds continue to arrive, while the first migrating Canada geese are seen on the marsh, arriving between the 12th and 15th of the month. Summering ducks begin to flock up while migrant waterfowl arrive to join them. The warblers, vireos, flycatchers, thrushes and other songbirds are passing through the area on their way south from northern Wisconsin and Canada.


As the summer songbirds begin to depart our region for their wintering areas well to the south, the Canada geese and ducks are reaching their peak numbers on the marsh. Herons, egrets, cormorants and other marsh birds depart as cooler temperatures and the coming of the first ice force them from our state.


While many people think of this as a winter month, the fall migration is still underway. The Canada goose flock often peaks in this month, while most of the other birds have long left the marsh. The rough-legged hawk is on the marsh to spend winter here well south of its arctic breeding grounds. Tundra swans may rest here during their long travels from Alaska to Chesapeake Bay. With the coming of ice cover the ducks and other water-dependant birds have long departed.


The migration comes to an end as snow cover forces the geese to move on and as winter finches, snow buntings and lapland longspurs settle down on the surrounding uplands. In certain years, snowy owls, short-eared owls, bald eagles and a variety of winter finches may be found in and around the marsh.

The geese of Horicon


Each fall, tens of thousands of Canada geese leave their Canadian breeding grounds and head for Horicon Marsh. Just as the geese flock to the marsh, so do the many visitors who come to hunt or just observe and thrill at this annual event. They come from all over the country and throughout the world to witness what is certainly one of the most amazing wildlife spectacles in the Midwest.

The geese that stop here in migration are part of the Mississippi Valley Population (MVP) of Canada geese. This is a mid-sized goose ranging from 7 to 10 pounds. In North America, there are several million Canada geese, consisting of 12 distinct subspecies. There are more than 1 million Canada geese in the MVP, with about 100,000 to 200,000 stopping at Horicon Marsh each fall. Another race, or subspecies, nests on the marsh and throughout Wisconsin, called the giant Canada goose.

Horicon Marsh is a migratory stop-over for the geese. In spring, they are on the marsh from late February or early March until mid-April. The marsh is a staging area that provides important spring food which will fuel their journey north and supply the energy for reproduction. Over the years, their average departure date from the marsh has been around April 21. It is the increasing daylight hours which stimulate the spring migration. From here, they migrate to their northerly breeding grounds, near Hudson Bay. They arrive on their breeding grounds around the end of April or beginning of May and begin to nest as soon as melting snow makes nesting sites available.

The Canada geese begin to breed when 2 to 3 years old. They will commonly mate for life, and will select a new partner if they should lose their mate. In the wild, the average life span for the Canada goose is about 6-8 years and have been known to live for more than 20 years. In captivity they may live over 30 years. They come north to take advantage of large available nesting areas. Here, they can avoid most nest predators and take advantage of the abundant food supply and long daylight hours. They normally lay a clutch of 5 eggs, with older birds having larger broods. Eggs are incubated for 28 days, with most families hatching within a few days of each other. The young grow fast, being full grown within only 2 months. Before the end of the short arctic summer, they must grow their flight feathers, fatten up and condition themselves for the long journey ahead.

It is the changing season which signals the fall migration. With the oncoming cold weather and shorter days of fall, the flocks move south. They travel together as a family and the large flocks we see overhead are collective family groups and nonbreeders. Loners, or single birds, are most likely sub- adults or non-breeding birds that have been at the marsh for some time and are not associating with family group. As the young follow their parents, they learn the migratory route from the experienced adults. The dramatic increase in the goose population at Horicon is the result of good management practices and due to successive generations of birds learning their way to the marsh.

When the large flocks are in flight, they travel in a typical V-formation. They apparently do this to reduce wind resistance and gain better visibility. On daily feeding flights, they fly from 100 to 500 feet high. In migration, they fly much higher, usually where they can find favorable winds. They average about 2,000 to 3,000 feet in altitude and have been observed at 9,000 to 11,000 feet.

The Canada goose can fly as fast as 60 mph, but usually prefers to go about 40 to 50 mph. They often leave with the passing of a cold front, so, with the aid of a strong tail wind, they can travel an easy 60 to 70 mph. At this rate, they can fly from Hudson Bay to Horicon, a distance of at least 850 miles, in about 15 hours. From here to their wintering grounds in southern Illinois, some 450 miles to the south, requires another 7 to 10 hours.

Geese photo courtesy of Jack Bartholmai

The geese arrive on the marsh around mid-September. They stay for about 4 to 8 weeks. The population peaks around late October to mid-November and departs by early to mid-December, as snow and ice cover the food supply and freeze open water resting areas. In most winters some geese remain in east-central Wisconsin, with the population size and distribution depending on open water, snow depth and weather conditions. While here, they feed on grass and grain and consume about a half pound of food per day. With so many geese in the Horicon area, crop damage to private lands is a constant concern. This is one of the many reasons for limiting the population size and distribution through regulated hunting.

The Canada goose has always been a part of Horicon, although the MVP geese did not stop here historically. The tremendous numbers which the fall migration brings is a more recent event. After the restoration of Horicon Marsh, the first flocks arrived in the late 1940's. Through management and the establishment of food plots, they were attracted to the area. Since then, their numbers have increased dramatically.

Mississippi Valley Population

Year Horicon Mississippi Valley
1948 2,000 170,000
1958 51,000 214,000
1974 214,000 304,000
1984 121,000 477,000
1987 236,000 725,000
1990 199,000 1,300,000

By the mid-1970s, the success of the program was beyond expectation, and the goose population at the marsh had become a matter of concern. Too many geese were stopping here! It became apparent that a potential disease epidemic would do tremendous damage to a large proportion of the entire MVP. Canada geese are susceptible to botulism, avian cholera, duck viral enteritis as well as other waterfowl diseases. Therefore, other marshes in east-central Wisconsin have been developed to accommodate Canada geese in fall, thereby spreading out the flock. In Wisconsin, the greatest number of geese still stop at Horicon, though others now also visit Theresa, Collins, Eldorado, Grand River, Pine Island and other state wildlife areas.

During their autumn visit, a close watch is kept on the Canada geese. A census of their numbers is regularly made by counting resting flocks from an airplane. Regulations and quotas are set each year to permit hunters to take about 25% of the population. Due to intensive research and management, the Canada goose has made a good comeback. From the very low population levels during the 1940s, it is probably more abundant today than it has ever been.

It is in the final analysis that we see the goose as a shared resource. It is managed regionally, with cooperation from the Canadian government, U.S. Fish and Wildlife Service, Wisconsin Department of Natural Resources, and conservation agencies in surrounding states. It is also shared by various interested groups of people, ranging in activities from nature observation to sport hunting. Horicon provides many recreational opportunities for people, and also resources and a rest stop for these wandering flocks of geese. It is only through continued management and public cooperation that we can ensure a healthy future for the Mississippi Valley Population of the Canada goose.

Fourmile and Cotton Island heron rookery

Within the marshland interior are several narrow islands which rise above the surrounding marsh. Like huge ships moored in a sea of cattail, they align themselves with the length of the marsh. These islands are the emergent tops of buried drumlins; a common glacial feature which was formed by the advancing glaciers of the last Ice Age. These hills were piled up as the glacier over-rode this land and carved out the Horicon basin. As the ice retreated, it created a moraine at the south end of the marsh, which held back the waters and filled the marsh, inundating these hills. Over the centuries, sediment accumulation has filled the marsh, so that today only the crests of these drumlins rise above the marsh to form these islands.

The largest of these islands is Fourmile Island, one of our State Natural Areas. Natural Areas, formerly called Scientific Areas, are unique areas that have been set aside for protection by the Natural Areas Preservation Council. They are selected from among the best remaining natural features in the state which contain nearly intact plant and animal communities or significant geological or archaeological features. Many natural areas contain features that remain essentially unchanged from presettlement conditions in Wisconsin. They are the last relics of what our state once looked like at the time when the earliest settlers arrived here.

Great Blue Heron

While most Natural Areas are selected for their unique native vegetation, Fourmile Island and nearby Cotton Island have been chosen for their unique bird population. Until recently, these islands supported the largest heron and egret rookery, or nesting colony, in Wisconsin. As many as 1,000 pairs of herons and egrets nested here. There were four species of birds in this colony; the great blue heron, great egret, black-crowned night heron and the double-crested cormorant.

Nesting records for Fourmile Island go back to at least the early 1940's. Although it is an important site to all of the large birds that use this area, it has been a particularly important area for the great egret. The egret is a threatened species in Wisconsin. At one time, these birds were more widespread in our state. Today, barely 10 known nesting sites remain with most of these being located along the Mississippi River. Being sensitive to disturbance and habitat loss, many colonies have been abandoned. When we lose a rookery, we lose the entire local breeding population since these birds do not nest alone.

Despite our best intention to protect these birds, there have been problems for the birds on Fourmile and Cotton Island. This time, man is only indirectly responsible for their fate at Horicon. Due to our present dominating land use, we have left these birds few alternatives for nesting sites, confining them to the Horicon Marsh and a few similar, isolated sites. Yet, even in this large wetland, few islands are large enough or suitably located to offer nesting opportunities for such a large population. Due to their success over the years, nature itself began working against these magnificent birds. There have been so many birds on this 15-acre island for so long that they were having a serious effect on it. At the peak of their population there were as many as 4,000 adults and young inhabiting the island. With a diet rich in fish and other aquatic food and so many birds nesting in so small an area, the accumulated guano, or droppings, was over-fertilizing the ground beneath. This resulted in changes to the soil chemistry which affected the trees that these birds nest in.

Essentially, they were destroying the very habitat on which they depended. In addition to guano accumulation, tree diseases, such as Dutch elm disease and oak wilt, have destroyed many large trees. It is likely that the birds were stressing the health of the trees making them more susceptible to diseases. As a State Natural Area, it is the state's policy to monitor this site and the birds' progress. Annual surveys keep track of the population size and nesting success for each species. Surveys have also been conducted on the composition and health of the forest on Fourmile Island. Management aims to allow the birds to adjust to their own changing conditions while taking measures to maintain suitable nesting habitat.

Other steps have been taken to help these birds remain at Horicon. In the winter of 1992-'93, wildlife biologists erected a series of artificial nesting platforms adjacent to Fourmile Island to provide additional nest sites and make up for the loss of trees on the island. During the following spring, birds were seen making use of some of these sites for building their nests.

Surprisingly, the birds seemed to sense the problems on Fourmile Island themselves and moved most of their colony onto nearby Cotton Island in the following spring. For several years, both Cotton and Fourmile Islands provided sufficient habitat to maintain this historical rookery. However, in spite of our best efforts to help the herons and egrets at Horicon Marsh, a natural disaster struck which ended their long-term tenure on these islands.

On May 31, 1998, a severe storm front swept across southern Wisconsin, creating winds of as much as 90 to 100 miles per hour. At the peak of the nesting season these winds hit the islands broadside, toppling trees, tossing young from their nests and destroying most of the nests. An estimated 550 nesting pair of great blue herons and great egrets were nesting on Cotton Island. After the storm, nearly half of the trees were felled and almost all of the nests had been destroyed. With the loss of the trees and the catastrophic results of this storm, these birds abandoned Cotton Island.

Great blue herons still nest on Fourmile Island, both in the trees and artificial platforms erected for them, but not in the numbers that it once held. The great egrets seem to have moved to a colony outside of Oshkosh which grew in the following year.

The lesson learned from this experience is that in spite of our best efforts to manage wildlife, there is nothing we can do to avoid these periodic, catastrophic events. However, like putting all of your eggs in one basket, when we crowd our threatened or endangered species into the last remaining suitable habitat we risk these kinds of losses from natural events. While our goal is to maintain a breeding population of herons and egrets at Horicon Marsh, we also need to think regionally in order to maintain a series of healthy rookeries. Just in case another such natural disaster should ever strike a nesting colony, we will assure that other populations will be able to maintain the species. Of course, we cannot manage to avoid severe storms, but we cannot confine wildlife to only a few islands of habitat and expect that they will last forever in an ever-changing natural environment.

As a State Natural Area, public access to both of these islands is strictly prohibited during the nesting season, from April 1 to September 15, to protect the remaining birds from disturbance. A good view of the island is possible from the DNR Service Center on Hwy. 28 or the overlook on North Palmatory Street. It can also be seen close up by canoeing on the east branch of the Rock River. When using this approach, please keep in mind that access onto the island is strictly prohibited. It is our intention to keep the herons and egrets here and allow them to rebuild their numbers as an important part of our marshland resource.

Last revised: Wednesday July 29 2015