How the Natural World Is Organized
Understanding Wildlife Populations and Communities
Understanding Plant Populations and Communities
Putting the Pieces Together
Myth or Fact?
Table 2.1 Problem Plants
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the Natural World
Preparing a wildlife habitat management plan
without having a basic understanding of wildlife and plant ecology
could be compared to doing your own car repairs without knowing
how an engine works - you might luck out, but you’re more likely
to run into trouble. This chapter explains fundamental ecological
concepts to lay the foundation for sound habitat management.
The management activities that biologists recommend
to help our natural world are based on ecology-the scientific study
of the interactions and interrelationships of plants, animals, and
their environments. In keeping with the human need to organize the
way we view the world, the scientific community has defined categories
for how the natural world is organized and functions. The broadest
unit is the ecological system, or ecosystem, a term used in the
field of ecology for the last hundred years. An ecosystem consists
of all the plants, animals, and other living organisms, plus their
environment, in a given area. The abiotic resources are the nonliving
portion of the ecosystem, made up of physical components such as
air, water, soil, bedrock, and climate.
The living part of the ecosystem is referred to
as the biotic community, or the groups of organisms living together
in a specific area. The terms plant community (or vegetative community)
and animal community refer to specific groups of organisms. Communities
are made up of collective populations of plants and animals. A population
is all the individuals of one species.
Wildlife management is conducted at each of these
levels: the ecosystem level, the community level, and the population
level. For example, the manipulation of water depth in a wetland,
by altering both the living and nonliving parts of the wetland,
would be considered ecosystem management. Still larger scale ecosystem
management would involve an entire watershed. An example of community-level
management is prescribed burning on a prairie. Such burning is conducted
specifically to manipulate plant communities. White-tailed deer
are managed at the population level in Illinois by regulation of
their annual harvest. Another recent example of population management
is bringing in prairie chickens from other states to increase the
diversity of the gene pool in our endangered Illinois flocks. To
be effective, wildlife management must be based on the systems and
processes inherent in nature. Understanding ecosystems is key to
successful wildlife habitat projects.
One of the more confusing aspects of understanding
ecosystems is size: How big is an ecosystem? Actually, an ecosystem
can be any size. A pond can be an ecosystem. So can a forest. A
crop field can be an ecosystem, as can a cliff, a cave, or a backyard.
But an ecosystem can also be huge-the Yellowstone ecosystem, for
instance, covers parts of three states and encompasses a variety
of community types. An example in our state is the Illinois River
ecosystem, which includes the river and its entire watershed. Yet
there are many smaller ecosystems within this larger one. The bottomland
forests and the backwater lakes found along the river can be viewed
as individual ecosystems.
The concept of ecosystems is broad so that it can
be used in a variety of circumstances to study and manage the natural
world. For property owners, the ecosystems most important to consider
for wildlife are grasslands, woodlands, wetlands, and croplands.
Later we will discuss how these relate to the larger landscape of
which a given piece of property is a part.
Be aware that there is some misused terminology
in the vocabulary of modern wildlife management. The terms ecosystem,
vegetative community, and habitat type are often used interchangeably.
In this book, discussion of "habitat type" generally refers to a
community dominated by a group of plants (woody for woodlands, herbaceous
for grasslands) or a community defined by a dominant physical characteristic,
such as the presence of water in an aquatic habitat, or by intensive
disturbance, as in croplands. Often biologists will also use the
term ecosystem as they do habitat, and they will further be referring
to a community type. You might hear a prairie called a prairie ecosystem,
a prairie community, or a prairie habitat. Since a prairie can be
all of these things in the purest sense of their definitions, all
of these usages are correct.
There are a number of important characteristics
to understand about ecosystems. One is that all their components,
both living and nonliving, are connected and dependent-to a greater
or lesser extent-on each other. For example, if you remove a large
predator species, like a wolf, from an ecosystem, a major shift
will result both in the prey populations and in the vegetation and
the other creatures that the prey feed on. The chain reaction continues
as the vegetation is altered and populations of small invertebrates
change, which affects in turn the soil and water.
Ecosystem complexity is also important to understand.
An ecosystem can be fairly simple, like an agricultural field that
contains only one planted crop, a few weeds, and a handful of animals.
In this type of system the interaction between plants, animals,
and physical components is relatively simple. But natural ecosystems
that have been less altered by humans usually have a much larger
variety of plant and animal species. The original Illinois prairie
ecosystem, for example, contained as many as 300 plant species.
The variety of an ecosystem's biotic community is often referred
to as its biodiversity. The more biodiversity within an ecosystem,
the more numbers and kinds of plants and animals are found there.
In wildlife habitat protection and creation, maintaining
or enhancing ecosystem complexity is usually a primary goal. A complex
ecosystem usually attracts and supports more wildlife. It is generally
more resilient to damage or complete destruction by uncontrolled
fire, disease, storms, and other disturbances, both natural and
human-induced. It is important to understand, however, that patience
is paramount in habitat restoration work. Habitat establishment
aimed at re-creating a complex ecosystem takes time. Establishing
vegetation is only the first link in a chain of events that will
eventually result in high-quality wildlife habitat. Soil microbes
need to establish; insects and invertebrates need to move in. In
time, animal species dependent on them will appear.
All species contribute something toward the healthy
functioning of an ecosystem. But too often people have decided arbitrarily
to eliminate some part of an ecosystem without regard for its importance
to the whole. A classic example has been the systematic destruction
of snakes-even by those who profess to be conservationists. Yet
snakes play a very important role in every ecosystem where they
live. Many landowners try to invite wildlife to their property,
but if an undesired creature shows up, it is killed or driven off.
There are instances in which wildlife can threaten
human-built structures-woodpeckers and wood-sided homes, for example.
If an animal is causing specific damage, control may be necessary,
although methods other than killing are usually possible and preferable.
It is common when landowners are trying to establish habitat that
certain species will hamper their efforts. For example, rabbits
and deer may feed on newly planted trees, shrubs, and wildflowers.
Beaver will sometimes cut down forest plantings or retard the establishment
of woody cover in stream-bank stabilization projects. In these types
of cases, some sort of repellent or control may be necessary.
The rule of thumb is this: Never eliminate wildlife
just because you don't like it. If an animal causes serious damage
or poses a serious health hazard, first consider methods of discouraging
it. If this fails and removal or elimination is necessary, consult
an Illinois Department of Natural Resources biologist. Most animals
are protected by law, and killing an animal without authorization
can result in a stiff penalty. Wildlife populations can often be
managed through regulated hunting and trapping so they don't become
Remember, each species has an important role in
nature, and if you're interested in building and maintaining the
best wildlife habitat possible, you need to make room for all wildlife
in the ecosystem.
Ecosystems are subject to a variety of processes.
Rather than being static, ecosystems are dynamic. Change is always
occurring as plants and animals struggle among themselves and with
other plants and animals for survival. Factors such as weather,
fire, and floods also create change in ecosystems. It is important
to understand, too, that not only do changes in the physical environment
affect the biotic community, but the reverse is true as well-changes
in the plants and animals can affect their environment. A significant
fluctuation in the plants or animals inhabiting a pond can change
the water's chemistry-a massive die-off of algae in a pond can deplete
oxygen, for example. Or if a disturbance removes a large portion
of tree and ground cover in a forest, sunlight penetrates to the
newly exposed soil and raises the ground-level temperatures. In
both of these instances, the change in the physical environment
would spur further change by affecting the biotic community-the
pond inhabitants in the first example and the soil and the leaf-litter
dwellers in the second.
Change of any kind in the biotic community or its
environment creates changes in the whole ecosystem. Change can be
favorable or unfavorable depending on the species in question. Usually
an ecosystem fluctuation favors some plants and animals and not
others. However, natural change in ecosystems should not be viewed
overall as a negative process.
Humans have caused great changes in Illinois ecosystems,
often to the detriment of individual ecosystems. But human-created
disturbances can also be used to undo some of the damage we've done.
Our ability to effect change in portions of an ecosystem for the
benefit of wildlife is at the heart of this book. A landowner can
establish specific plants on a site, manipulate water levels in
a wetland, or introduce fire-all of which, if done for a specific
purpose, can improve conditions for wildlife.
Let's address more specifics on the biotic components in ecosystems.
To begin understanding the life requirements
of wildlife, we need look no farther than the needs of a familiar
animal: the human. Just like us, wildlife require four basic elements
to live: water, food, shelter, and space. Food and water are prerequisites
to sustaining life; shelter-from weather, from enemies, and for
raising young-perpetuates life. And all animals need physical space
for themselves and their families, although the amount needed varies
Habitat is what provides all of these elements
for wildlife. The term habitat is used in several ways, but it is
basically defined as a living environment. The term can be used
singly (an animal's habitat) or collectively (wildlife habitat).
The word is also used to define a type of living environment. Our
management recommendations address four predominant Illinois habitat
types: grasslands, woodlands, wetlands, and croplands.
Some wildlife species may be able to satisfy all
four basic needs in one type of habitat. Other species have complex
needs and require several habitats to secure adequate food, water,
shelter, and space. The collective area needed by an individual
animal to meet its normal living requirements is known as its home
An animal's home range should not be confused with
its natural range, which refers to the geographic area in which
the species can be found. For example, the natural range of the
eastern chipmunk includes eastern Canada and the eastern half of
the U.S. But an individual chipmunk's home range is from less than
half an acre to three acres, depending on local conditions.
Home-range size applies to individuals within a
species and varies between species. For some, such as the white-tailed
deer and the great-horned owl, a home range may encompass one to
four square miles. The home ranges of other animals, such as the
shorttailed shrew and the spotted salamander, may be just a quarter
of an acre. Still other species, including migratory hummingbirds
and warblers, have home ranges that may vary seasonally and may
be located on two continents. The home range may also vary slightly
for any species depending on the quality of available habitat.
Here's an illustration of a species' home range:
The ring-necked pheasant has needs that differ between seasons,
and to meet those needs it must use several habitats. During much
of the year, this bird can be seen roaming the open agricultural
fields of central and northern Illinois. For breeding and nesting,
however, the female needs to find an undisturbed (unmowed) grassy
field that will hide her eggs and provide insects for her newly
hatched clficks. And during severe winter weather, the birds need
thick, erect vegetation, such as cattails, prairie grass, or brushy
cover, for shelter. The area required to meet these needs, generally
one square mile in Illinois, is the pheasant's home range. However,
individuals have been known to disperse as far as 15 miles when
needed to fulfill their living requirements.
When an element necessary to a species' survival
is in short supply or completely absent, it is referred to as a
limiting factor. Because wildlife have complex and varied needs,
the lack of any particular element can limit population size or
even prevent a species from inhabiting an area. For instance, a
woodlot may be filled with mast-bearing oak and hickory trees that
produce enough food for twenty squirrels. But if the woodlot contains
only a couple of trees with cavities, the squirrel population will
be limited by the availability of secure sites for raising young.
The area probably cannot support twenty adult squirrels because
of a limiting factor-insufficient nesting sites.
Most of today's limiting factors for Illinois wildlife
are caused by habitat degradation and elimination. Natural occurrences
such as weather extremes, disease, and lack of food can also be
Some landowners become disappointed that habitat
development or enhancement doesn't produce immediate results, or
the results they expected. They wonder why their grass planting
has failed to attract quail or why they don't have wood ducks in
their newly created marsh. The reason is probably a missing habitat
element or an unapparent limiting factor that has prevented the
local population from expanding into the landowner's "new" habitat.
Landowners should not let such a situation discourage their habitat
development; improvements targeted at a specific species often work
with time, provided the property is within the animals' normal geographic
range. Sometimes a particular limiting factor will be eliminated
after habitat plantings have become well established. For example,
the simple presence of grass may not be enough for certain grassland
birds. Some species, such as the Henslow's sparrow and the sedge
wren, need undisturbed grassy areas that have accumulated a couple
years of dead grass thatch. A first-year planting cannot provide
Ecosystems are dynamic, and the populations within
them fluctuate from year to year. But on average, all habitats can
support only so many animals of any given type. This limit is defined
as an area's carrying capacity. When too many animals of a species
are born into or immigrate into an area that is at its carrying
capacity, some animals will have to go, either by leaving or by
dying. The carrying capacity for any species varies seasonally and
yearly, depending on the presence or absence of limiting factors.
During a drought year, for example, fruit-bearing trees and shrubs
may produce less fruit than usual, and the carrying capacity of
the drought area would likely be reduced for the wildlife species
that subsist on the fruit.
Many species produce an overabundance of offspring
each year to ensure an adequate survival rate. If"new" suitable
habitat has been created near existing habitat, some of the surplus
animals will move into the new area. But if there is no new habitat
for dispersal, the surplus animals are eliminated through starvation,
predation, or disease. Hunting and trapping are regulated to use
the surplus without destroying the base population.
The principles of carrying capacity continually
determine population sizes and viability. Landowners trying to increase
wildlife populations must understand that wildlife cannot be stockpiled;
populations will always be limited by the amount and quality of
habitat available to them.
Although the biotic community includes all the
living organisms, plant and animal, occupying a particular area,
it is often referred to by its dominant vegetation. For instance,
in Illinois you might hear of an oak-hickory forest community, a
cattail marsh community, or a prairie grass community.
However, while communities are generally identifiable,
the landscape doesn't always consist of neatly defined parcels.
Where different vegetative communities meet there is often some
overlap, creating a transition zone called an ecotone. Ecotones
are often subject to great fluctuation because disturbances usually
affect the two adjoining communities differently. For example, the
ecotone between a forest and a grassland would contain some shrubby
plants and maybe a few scattered trees, with lots of grassland plants
beneath them. If a fire were to burn the grassland and the edge
of the woods, some of the woody plants in the ecotone would be destroyed
and the grass would flourish. The edge of the woods would be opened
to sunlight, creating more favorable conditions for the grassland
plants. The change would allow the grassland to advance a little
into the forest.
While ongoing change is not always apparent, plant
communities are dynamic rather than static entities. All land in
Illinois, whether backyard, corn field, or bottomland forest, is
subject to a process called succession. Succession describes the
continuous, fairly predictable change of plant species and plant
communities over time. The ongoing competition among various plants
and plant communities to establish themselves on the landscape is
why succession occurs. How it occurs is a matter of biology. Different
types of plants have different life cycles and adaptations for surviving
in the environment, and over time some plant species and groups
of plants will naturally be better adapted to local conditions.
When does succession occur? It happens continually
on a small scale. Large-scale succession of whole plant communities,
though, occurs whenever there is a major change in an area's environment.
Natural disturbances such as floods, tornados, and severe icestormscan
damage or destroy an existing community, and a major successional
course usually begins.
In Illinois, the human activities most often leading
to succession of plant communities are abandonment of agricultural
fields and logging. Yet the process of succession can be observed
right outside our homes. Any time a tree pops up in an unmowed area
or weeds appear in a newly plowed garden, succession is in progress.
What keeps our backyards from becoming woodlands are lawnmowers,
herbicides, and garden tillers.
If it is allowed to proceed without disturbance,
plant succession has fairly predictable stages and outcomes. Generally,
in much of Illinois today, the process of succession in a bare field
starts with the pioneer stage of annual plants, which eventually
are largely replaced by perennial herbaceous plants, then shrubs
and trees, and ultimately a mature forest. Here's an example of
what could predictably happen if an upland central Illinois crop
field were permanently abandoned, with no further human interference:
First it would be iny'o \ded by herbaceous annuals such as foxtail
and ragweed. After two or three years, perennial herbaceous plants
like goldenrod and milkweed and grasses like smooth brome or bluegrass
would get firmly established, outcompeting and replacing many of
the annuals. Assuming a local seed source was present, after another
two to three years, woody species such as dogwood and elderberry
shrubs and seedlings of invader trees such as silver maple, eastern
redcedar, mulberry, and box elder would begin appearing. As the
woody species developed extensive root systems and increasingly
shaded the ground, they would dominate the site. As the invader
trees grew, a young forest would develop. Eventually (in twenty
to forty years), the trees would sort themselves out, and certain
species would dominate to form the canopy of a maturing forest.
Most of Illinois' openland habitats-grassland and
cropland would ultimately revert to woody cover if left undisturbed.
Which plants would appear during the course of succession would
be dictated first by what seed sources were in the area and second
by the specific physical conditions of the site (drainage, soil
type, slope, etc.).
When disturbance is introduced during succession,
the process can be either retarded or encouraged. Much of the Illinois
land used for agriculture is intentionally kept at an early successional
stage by periodic tillage. For the landowner trying to reconstruct
some type of habitat, such as a woodland, minimizing tillage, mowing,
and other disturbances should encourage successional progress to
that targeted community type. For other habitat reconstructions,
such as grass lands, periodic disturbance (fire, mowing, discing,
herbicides) is necessary to prevent woody encroachment and to help
the herbaceous plants flourish. Strange as it may sound, many mature
communities have evolved to actually depend on certain disturbances
to prevent succession. For example, many oak-hickory forests need
fire to keep them from succeeding to a forest of maple and other
shade-tolerant species. Many grasslands need fire to prevent them
from succeeding to woody cover. Bottomland wetlands need periodic
flooding to flush accumulated organic debris so they do not succeed
Manipulating the succession of habitat, by either
retarding it or enhancing it, is the basis of much of wildlife habitat
management. But it is important to remember that even if you're
managing for an eventually "stable" community, there will always
be some ongoing successional change. You can't freeze nature into
an oil painting of exactly the plant species you want, just where
you want them. This doesn't mean that you won't eventually have
a prairie or woods that seems relatively unchanged over the years.
What it does mean is that certain plants you introduce during establishment
of your habitat may, for one reason or another, not be able to persist
or compete with the others and will eventually disappear.
Here are some additional points to be aware of about succession:
It is easy to create early successional habitats
simply by applying some sort of disturbance. But we cannot reconstruct
a mature, later-successional-stage community in a short period.
For example, we must simply wait out the time necessary for
trees to grow to their mature state. We can, though, have limited
impact on the efficiency with which that growth happens. For
example, we can plant desirable trees such as oaks and hickories
and at the same time suppress shade-tolerant trees to give the
slower-growing oaks and hickories maximum growth opportunities.
Given the lengthy time it takes to re-create mature communities,
especially the forested types, it should always be a priority
to preserve those that already exist.
The process of succession in Illinois has
been affected by the widespread establishment of non-native
plants, which sometimes outcompete native species. As a result,
we must often "assist" in succession if the goal is to establish
a diverse, specific community of native plants. Fescue, for
example, can become so thick that it prohibits the establishment
of most woody vegetation. And aggressive exotics such as Tartarian
or Amur honeysuckle can suppress native, slower-growing trees
such as the oaks. These exotic shrubs can quickly dominate and
shade the forest floor and prevent sun-loving oak seedlings
Since wildlife have specifi,c habitat needs,
succession of plant communities also results in some continuing
change of corresponding wildlife communities.
Because controlling or encouraging succession is
pivotal in wildlife habitat management, chapters 4, 5, and 6 discuss
succession for each habitat in detail.
Understanding how plant and animal populations
function and interact with their environment builds a foundation
for good habitat management. The next step is to translate that
knowledge from these pages into the real world-the everyday management
of your parcel of land. But for wildlife the "real world" isn't
defined by legal property boundaries. In our state, their reality
is the collective landscape we call Illinois, an intricate mosaic
of overlapping home ranges of various animal species. Since wildlife
operate within their own boundaries and not those of humans, we
must look at the bigger picture to make the best land management
We have discussed habitats as individual units of management. When
we look at the landscape, these units form various patterns. While
the quality within these units is important, the size and arrangement
of these units on the landscape also affect their suitability for
various wildlife species.
Interspersion refers to the proximity of different
habitat types. The interspersion of habitats is directly related
to the size and arrangement of the units, and it affects what animal
species will occupy them. Several small tracts of different habitat
types in close proximity means there is high interspersion, and
Interspersion is an important consideration in
habitat management planning. Some species may require large, unfragmented
tracts of a single habitat type (no interspersion). Other wildlife
may need several habitat types (high interspersion), all of which
can be small patches but that must be spaced close together. Many
species thrive in edge habitat, which is created with higher interspersion.
Edge habitat-which exists where two habitat areas meet, such as
a brushy fencerow and a crop field or a grassland and a forest contains
animal species from both adjacent habitats and also supports wildlife
that prefer edge, such as cardinals, cottontails, and common yellowthroats.
Two illustrations reveal the importance of considering
interspersion. Ovenbirds require several hundred acres of unbroken,
mature forest for successful breeding, and they have evolved to
procure all the necessary elements from that one habitat in the
summer. Smaller patches of habitat make them vulnerable to competition
from other species, such as the brown-headed cowbird, and to increased
predation by abundant edge-dwelling predators like raccoons. On
the other hand, cottontail rabbits need several types of habitat,
and because they are not extremely mobile (as most birds are) they
need to have the habitats close together. They are often found in
edge habitats as opposed to deep forest interior.
Interspersion is not the only consideration that
influences habitat suitability. Whether valuable habitats are isolated
or connected also determines the landscape's usefulness to most
wildlife species. For example, let's say a thirty-acre woodland
sits in the middle of 900 acres of crop field, and the nearest woody
cover is three miles away. Less mobile species of wildlife, such
as reptiles, amphibians, and small mammals, would be unable to travel
between the two woodlands. The animals in the thirty acres would
be isolated and more susceptible to the effects of inbreeding and
adverse weather events. As species disappeared from the island woods,
the biodiversity of this forest would decrease and it would eventually
support only mobile generalist species, like white-tailed deer and
If, on the other hand, strips or fencerows of woody
vegetation existed between the two woodland tracts, genetic intermixing
could occur via these corridors. Corridors used to be more numerous
in Illinois. The elimination of hedgerows coupled with our continued
penchant for "tidy" landscapes has led to the removal of many of
our weedy, brushy, and tree-filled windbreaks and fencerows.
Earlier we discussed biodiversity within ecosystems.
When we look at the Illinois landscape, biodiversity between ecosystems
is also critical. The Illinois Natural Areas Inventory that was
conducted in the late 1970s categorized, for the first time, nearly
all of the natural community types historically known for our state.
Approximately eighty-five communities were recognized. Preserving
and restoring this diversity of distinct communities on the Illinois
landscape is essential to preserving our variety of wildlife.
As you can probably now see, managing for wildlife
can include many elements. So how do you, the individual landowner,
determine the appropriate habitat to construct or preserve-in the
right place and of the right size-for the myriad of Illinois wildlife?
While species are sometimes managed individually,
the most efficient way to manage is to consider groups of species
that occupy common habitats. This is why most land management revolves
around habitat types. Many species use several habitats but prefer
one primary type. Generally, if a woodland is managed for woodland
wildlife, most species that use this habitat will benefit.
Trying to restore Illinois habitats as we believe
they existed prior to European settlement is a way to benefit native
species with specific requirements. (See The Natural Divisions of
Illinois referenced for a better understanding of the historic Illinois
landscape.) While this book discusses the use of certain non-native
plants, the primary emphasis is native plants and plant communities.
Where possible and practical, we should use nature as the gold standard
to measure our actions.
One of a landowner’s most important management
considerations is to take a three-dimensional view of wildlife habitat.
From the treetops to deep in the soil to the horizon beyond a properly
boundary - this is the habitat where wildlife live. Habitat types
and home ranges transcend political and legal boundaries and stretch
beyond immediate human vision. Try to view the landscape from a
Often we act by considering only short-term economic
factors. Taking a more holistic view is usually the best approach.
Unfortunately, not thinking broadly enough h~s resulted in a fragmented
effort to conserve and restore Illinois' wildlife habitat. But government
agencies and private conservation organizations have recently begun
to consider a larger "landscape level," or ecosystem-based, approach
to their wildlife management activities. Landowners ought to do
the same if they desire to restore and retain a diversity of wildlife.
The final point to be learned from lessons of ecology
is that wildlife are affected, either negatively or positively,
by whatever a landowner does to his or her property-including doing
nothing. No Illinois landowner can be passive and claim not to be
part of the problem or the solution. The fate of Illinois wildlife
rests in the hands of private landowners. With a foundation of basic
environmental knowledge, each landowner can make land management
choices that build the sustainability of our natural resources.
There are many widely held beliefs about wildlife
that are accepted as fact. On the surface these beliefs may seem
very logical. However, once you understand how the natural world
functions, you question them. Understanding concepts such as plant
community succession, basic needs of wildlife, and carrying capacity
helps dispel many of these myths. Some common myths and the related
facts are detailed here.
Myth: Wildlife are starving:
Wildlife that feed on seeds or grains are far from starving
in Illinois. With nearly 80% of our land used for agriculture, and
with conservation tillage increasing in our state, food for many
wildlife species is abundant in crop fields. And most seed-eaters
opt for a variety of foods, including weed seeds and other plant
materials. Wildlife can experience hardship in winter when ice or
deep snows blanket the ground for days or weeks. But it is the lack
of cover, not of food, that usually kills wildlife in the winter.
A different aspect of wildlife food supply is of
serious concern. Widespread pesticide use on our yards and farms
and loss of vegetation, such as small grains and legumes, have greatly
reduced insect populations. Hundreds of bird, mammal, reptile, and
amphibian species depend on these invertebrates for food. They are
an essential food for young pheasant and Bobwhite quail chicks,
and many songbirds eat insects almost exclusively. While many people
would argue that we still have more than enough insects, certain
wildlife species are likely experiencing a reduction of necessary
foods in some instances.
Myth: Hunting and trapping are the reason many wildlife species
and trapping have not contributed to the decline of wildlife since
the days of unregulated mass harvesting for markets. Today both
activities are carefully controlled by state and federal conservation
agencies, based on the principle of carrying capacity. Harvest limits
are set in accordance with statistical analyses of species' year-to-year
populations. Species that are hunted and trapped are those whose
populations are flourishing enough to produce a surplus.
Myth: Releasing hand-reared birds builds up local populations.
Facts: Numerous studies have shown
that pen-raised birds such as quail and pheasants don't survive
long in the wild once they've been released. They don't fear predators,
don't know how to seek cover from inclement weather, and may be
inept at finding food. And if an area is already supporting all
the animals it can (it is at its carrying capacity), adding new
individuals only results in a surplus that is eliminated in a few
months. Releasing pheasants or quail to supplement a hunting program
can be acceptable, but doing it to increase an existing population
is a waste of time and money. A better use of those resources would
be expanding existing habitat to allow natural population growth.
Some people wonder, if we can successfully raise
and release certain endangered species to reestablish a population,
why won't it work for all wildlife? Most captive-breeding programs
for endangered species work to reestablish an animal to a former
range where habitat conditions have taken a turn for the better
or where a harmful factor or element, such as the insecticide DDT,
no longer threatens a species. Depending on the species, the animals
are bred and released into the wild at a young age, or they are
raised in a semi-wild environment, carefully controlled to simulate
a natural situation.
Myth: Because the state has successfully
established new populations of some animals through trap-and-transplant,
this should work for any species.
Facts: The wild turkey and the
river otter are two species that practically disappeared due to
habitat elimination, habitat degradation, and uncontrolled harvesting.
Even when these factors improved, physical barriers prevented both
species from reestablishing in their former ranges.
The wild turkey was over harvested at the same
time its habitat was disappearing. Once harvesting was banned and
then subsequently regulated, and some habitat restoration had occurred,
the species still wasn't recovering. The birds wouldn't cross towns
or large expanses of open agricultural land to repopulate formerly
inhabited areas. Biologists assisted by transplanting the wildlife.
The river otter declined initially due to unregulated
trapping, and it suffered further declines from the poor water quality
that developed in Illinois around 1900. Water quality has improved
significantly in some Illinois rivers and streams,.but the otters
cannot always travel long distances to reinhabit their recently
improved former habitats. Transplanting worked because the factors
negatively affecting the species were resolved.
There are additional animals that could be successfully
transplanted, but only after long and careful evaluation by qualified
biologists. Numerous habitat conditions must be met before any species
can be reestablished. One or more habitat elements are missing for
many of the species that have declined in or disappeared from Illinois,
in which case transplanting would not be successful.
Myth: The best thing I can do for my land is to let it go "back
to nature. "
all habitats in Illinois today, natural or created by humans, need
some form of management.
We have altered the landscape and the dynamics
of nature so drastically in our state that most systems are hindered
in returning to a native and natural state without our help. Even
the high-quality remnant communities scattered around Illinois usually
need some assistance to respond to the onslaught of changes we've
thrust onto the landscape. For example; we eliminated the natural
process of fire, but we now understand its critical role in sustaining
many natural communities. And the unabated march of invasive exotic
plants into our natural communities will not cease without our help.
Myth: New and improved varieties of shrubs
and trees are better to plant because they grow much faster and
provide better habitat.
Facts: The Illinois Department
of Natural Resources, along with other agencies such as the USDA
Natural Resources Conservation Service, promoted this concept in
decades past. However, long-term research has shown that introducing
non-native vegetation into native plant communities can have many
dire consequences. This has been demonstrated by Tartarian and Amur
honeysuckle and multiflora rose. Illinois biologists have not recommended
non-native woody plantings for more than twenty years, and they
suggest only a few non-native herbaceous plants, such as pasture
grasses and legumes, for wildlife. But plenty of non-native varieties
of herbaceous plants, shrubs, vines, and trees are still commercially
available. Landowners should use only native plants in rural habitat
projects, and where possible in backyard habitats as well. Many
of our worst invasive exotic species in Illinois, purple loosestrife
and garlic mustard, for example arrived here as flower or herb garden
plantings and escaped "to the country" to set up permanent camp.
Table 2.1 shows some of the problem species that should not be planted,
even in backyards.
Even with apparently native plants, careful shopping
is required. Plant scientists have made many advances in selecting
and developing varieties. The results have brought us "super" varieties
of many native species. Switchgrass, a native Illinois prairie grass,
is a good example. This grass has proven to be good forage for cattle,
and plant scientists have developed more aggressive varieties to
improve production. When an improved variety of switchgrass is planted
with other native prairie plants, it usually takes over and crowds
out the companion species during the first few years.
Problems can arise when landowners buy species
that are native to Illinois but whose seed is collected elsewhere.
Many landowners shop by mail to save money on prairie plants and
seed. It is always better to purchase plants and plant seed derived
from stock grown in Illinois. This practice keeps local genetic
Myth: There are too many predators.
When people think of predators, animals such as foxes,
coyotes, bobcats, and hawks usually come to mind. Yet many other
species are also "predators." Herons are predators of fish, salamanders
eat worms, shrews sometimes feed on other rodents, and bluebirds
and robins consume beetles, spiders, and other invertebrates. Whatever
the species, any wild predator will only increase in proportion
to the amount of available prey.
There are two Illinois predators, though, whose
abundance doesn't vary with fluctuating prey populations. These
animals have increased dramatically in the last several decades,
and their disproportionately high numbers on the Illinois landscape
are seriously threatening the natural stability of many ecosystems.
These "new" non-native predators are domestic dogs and cats. As
our human population grows and expands into rural areas, pets have
become a dominant force on the land. Unfortunately, their overabundance
is impacting some birds, mammals, reptiles, and amphibians. Cats
in particular, will hunt whether or not they're hungry. So keeping
a pet well fed cannot solve the problem. When possible, landowners
should confine pets to a . yard area, and put bells on their collars
to alert wildlife to approaching danger. Other measures include
having pets neutered and controlling the dumping of unwanted animals.
- Amur honeysuckle
- Asiatic daylily
- Autumn olive
- Burning bush
- Canada thistle
- Chinese pea-tree
- Chinese yam
- Climbing euonymus
- Crown vetch
- Dame's rocket
- European buckthorn
- European water milfoil
- Garlic mustard
- Glossy mustard
- Janpnese honeysuckle
- Multiflora rose
- Musk thistle
- Narrow-leaved cattail
- Purple loosestrife
- Purple vetch
- Purple wintercreeper
- Reed canaru grass
- Round-leaved bittersweet
- Russian olive
- Silver poplar
- Sweet clover
- Tall fescue
- Tartarian honeysuckle
- White mulberry
- Winged wahoo
*While some of these species have been commonly used for backyard
landscaping and wildlife habitat, they should not be planted.
Comprehensive Plan for the Illinois Nature
Preserves System. Part 2: The Natural Divisions of Illinois. J.
E. Schwegman. 1973. Illinois Nature Preserves Commission.
Illinois Habitat Posters. [Full-color posters
that depict Illinois habitats and the organisms that inhabit them.]
Illinois Natural History Survey.
Illinois Wilds. M. R. Jeffords, S. L. Post,
and K. R. Robertson. 1995. Phoenix Publishing, Urbana, IL.
Illinois Wildlife and Nature Viewing Guide.
M. K. J. Murphy and J. W. Mellon. 1997. Illinois Department of Natural
Technical Reports on Bioregional Resources
of Illinois. [Series covers 21 bioregions of the state.] Illinois
Department of Natural Resources.
The Audubon Society Nature Guides. [A series
of guides published by Knopf and divided by ecosystem: grasslands,
wetlands, eastern forests.]
For more information about the Illinois Conservation Wildlife Plan, please
Comprehensive Wildlife Conservation Plan Coordinator
Illinois Department of Natural Resources - Office of Resource Conservation
One Natural Resources Way
Springfield, Illinois 62702-1271