keeping warm – Discover-Nature

Midwestern Prairie

Grasslands make up the largest habitat in North America and cover about one-quarter of the Earth’s surface. There are many different types of grasslands, each with its own descriptive name. Prairie, found in North America, is from the French word for “meadow;” steppes, found in Asia, is Russian for “flat, grassy plain;” pampas, found in South America, is from Quechua meaning “flat surface;” and veldt, found in Africa, is from Afrikaans meaning “field.” In all of these areas, grasslands are characterized by flat or gently rolling countryside.

From upper left: The African veldt by Cello8, May 2007; Sunrise on the Mongolian steppes by Nicolas Mirguet, Apr 2011; Pampas grasslands, Uruguay, South America by Guilherme Boettcher, May 2010; Nachusa Grasslands, Lee County, Illinois by Justin Meissen, Jul 2007

Prairies in Illinois were formed by the action of glaciers retreating northward at the end of the last ice age. Massive ice fields compacted the soils and flattened the landscape. Many areas retained much of the melting ice in ponds, creeks, and rivers. These provided much needed moisture to help establish the new flush of vegetation that moved in as the climate warmed.

White River Prairie, Wisconsin by Joshua Mayer, Aug 2016

Several different types of prairies can be found, differentiated by the mixture of grasses and flowering plants, called forbs. We classify prairies as wet, mesic, meaning moderately moist, or dry. The determination is made based on how much water is retained in soil layers, but can be greatly influenced by temperature, rainfall amounts, and fire. Grasses have narrow leaves, can grow in drier environments, and are the dominant plant type in most prairies. Forbs have broad leaves and require more moisture than grasses. Prairie plants often have deep root systems to access water and nutrients.

From upper left: Big Bluestem, Andropogon gerardii by Matt Lavin, Sep 2019; Rattlesnake master, Eryngium yuccifolium by Adam B, Jan 2017; Grey coneflower seed heads, Ratabida pinnata by JanetandPhil, Nov 2010; Frosty Prairie dock, Silphium terebinthinaceum by Anne McCormack, Dec 2010; Indian grass, Sorghastrum nutans by Douglas Mills, Sep 2015

Animals that inhabit midwestern prairies are adapted to this habitat. They are able to find water and food in drier conditions, when water is scarce. They avoid the hazards of fire sweeping across the landscape. They keep warm during cold winter months. They avoid predators in a landscape with few hiding spaces. Many species are able to burrow underground for warmth, to avoid fire, and to escape predators. Others live near the ground in thicker vegetation that provides cover from wind, cold, and attack.

From upper left: American toad, Bufo americanus by Alan Huett, Jul 2008; Sedge wren, Cistothorus platensis by Joshua Mayer, Jul 2015; Thirteen-lined ground squirrel, Spermophilus tridecemlineatus by ChristaR., Nov 2016; Prairie kingsnake, Lampropeltis calligaster by Peter Paplanus, May 2022; Northern harrier, Circus hudsonius by Wendy Miller, Dec 2010

At this time of year, prairie plants are starting to go dormant and many bird species are migrating southward to warmer climates where food and water is abundant. It is a great time to get out and observe plants as they set seed and surprise us with the many hues of autumn. Birds are abundant as flocks fly overhead on their migration. Birds that spend the winter here are searching for areas that will provide seed and cover during the coming cooler months. Other animals are out to gather plants for insulation in their winter dens or seeds to store in their larder. Keep your eyes and ears open as you walk the prairie paths this month.

Midewin tallgrass prairie preserve, Wilmington, IL by CheapShot, Jun 2012

Bird Eggs

It is spring in the northern hemisphere, and many birds are claiming territories, finding mates, and establishing nesting sites. Raising new families will take most of the summer and early autumn. As we watch birds who have laid their eggs, it may seem that not much happens until the young hatch, but there is lots of activity taking place.

^{RWBB calling by mirceax from Getty Images}

An ovum, the female reproductive cell, starts its journey to become an egg in the oviduct where it is fertilized by stored sperm from a male and encased in a glob of protein-filled gelatin to form a yolk. Additional proteins, known as the albumin or egg white, are added to nourish the embryo as it grows inside the egg. Calcium carbonate, a mineral added by special cells in the bird’s uterus, encloses the gelatin-like mass of protein and embryo, slowly hardening into the egg’s shell. Egg shells are not completely solid, but are perforated with many minute holes that allow air to reach the developing embryo. Pigmentation is squirted onto the shell adding color and pattern to the outside. A coating of protein determines the outer texture of the egg which may be smooth, glossy, dull, rough, or powdery.

^{Egg collection, Jurica-Suchy Nature Museum, Benedictine University, Lisle by DonArnold}

The total number of eggs laid at one time is called a clutch and some bird species lay only one a year, but many species produce two, or more, annually. A consistent number of eggs is found in each clutch, although additional clutches in the same year may contain fewer eggs. Eggs vary widely in size, shape, and color among various bird species. Egg shapes may be determined by the location of the nest. Cavity nesters tend to have rounded eggs, while cliff dweller’s eggs are often oval with a broad end on one side and a pointed end on the other to prevent the egg from rolling very far. Where a clutch has a greater number of eggs, pointed shapes fit into smaller spaces enabling the mother to easily cover them all when sitting on the nest.

^{Nesting female hummingbird by jaypiercestorffphoto}

Incubation is the process of keeping the eggs warm. An adult usually develops a brood patch underneath its belly where feathers and down disappear and blood vessels close to the skin’s surface can warm the area that is in direct contact with the eggs. Incubation periods are consistent in each species, but may be lengthened by abnormal cold spells.

^{Blue robin eggs in nest by Dennis Flarsen, Pixabay}

^{Western bluebird eggs by Summit to Seashore Birding, Sep 2007}

Color is added into the shell material before it hardens. Colors may vary in hue and saturation on individual eggs, and the deepest hues are often found at the largest end. Pigments are chemicals with complex molecular structures that produce color when mixed with water. Birds have two pigments: reddish-brown hues and bluish-green hues. Here are several theories as to why eggs have markings, but exact reasons are not known.

Heavier pigments are often found in birds that lay their eggs in open, exposed environments, and the markings may serve as camouflage. Many cavity nesters lay white eggs, which are well hidden from other birds, predators, and the sun. Some eggs laid in exposed nests may still be brightly colored, but covered by the female most of the time.

^{Quail eggs showing pigmentation by Piyachok from Getty Images}

Darker colors and markings are often found among species that breed in cooler climates. Pigments are known to absorb UV radiation from the sun and not allow it to harm a developing embryo. But, light absorption by an area of pigmentation generates more heat inside the shell, which may also be harmful. Pesticides and other chemicals in the environment can cause thinning of the shell casing, making them more susceptible to breakage. Pigments tend to gather at weaker spots in the shell casing and have been shown to strengthen the shell.

Several aspects of bird egg development are not yet understood, and many theories are under investigation. An interesting question currently under review is whether a bird, or another animal such as a predator, sees different aspects of the light spectrum than humans. If so, what do birds see when they look at an egg? A new bird’s life starts in an egg, a small and wonder-filled package that has been much studied and yet still presents many unanswered questions.

To learn more, consider visiting your local nature museum.

The Jurica-Suchy Nature Museum at Benedictine University in Lisle, Illinois, has an extensive egg collection displayed by clutch size and covering almost 200 bird species.

Arctic Adaptations

The Arctic circle will experience its coldest time of year this month, as the sun does not rise in the visible sky between October and March. Animals that live in this part of the world have developed many adaptations for living easily and comfortably in these extreme conditions.

Most arctic animals are either very small or very large. Small animals, like arctic foxes and arctic hares, easily burrow under snow and ice to create comfortable dens. Tight entrances and long passages help keep air trapped under a thick layer of snow that acts as insulation, minimizing contact with the much colder external air. Body heat from the den’s occupants warms the temperature even further. Large animals also use dens including ringed seals and polar bears.

_{Polar bear on ice pack by Christopher Michel, Jul 2015; Musk Ox by Malcolm Manner, Mar 2013; Moose & frozen sagebrush by Steven Robinson, Oct 2017}

Larger animals have a high body volume to surface area ratio, as is found in the shape of a ball. Internal heat is generated relative to body volume, and it is lost relative to surface area. Large, tubby animals including polar bears, musk oxen, and moose generate lots of heat while losing very little. Other adaptations help maintain this balance of heat and loss.

Shaking polar bear by TambakoTheJaguar, Mar 2016

Thick, hollow fur/hair traps air inside each strand as well as underneath its heavy layers. Paws are covered in thick fur for stability, grip, and warmth. Long, furry tails can be used as blankets to wrap around bodies and noses. Oil secreted from special glands coat outer layers of fur, hair, feathers, and skin protecting the animal from direct contact with freezing waters. In addition, oil repels water so that it quickly runs off when the animal is on land, keeping them dryer and less exposed to cold air wicking away body heat.

Huddling fur seals by Michael Sale, Nov 2006

Huddling reindeer by Ben Townsend, Nov 2005

Polar bears, arctic foxes, walruses, seals, and musk oxen all have blubber, a thick accumulation of body fat just below the skin layer. This prevents cold from penetrating the body cavities that contain vital organs. It can also be utilized for energy for movement or to create additional body heat. Huddling is another method used to prevent cold from getting to the center of a mass. Used by musk oxen, arctic foxes, walruses, seals, and arctic hares, staying close with a large group is warm and comfortable.

Reindeer, also known as caribou, are known by their long noses. Air follows a twisty route through the nasal passage before reaching the lungs. Interior walls contain many blood vessels close to the surface that warm the passing air up to seventy degrees before it enters the lungs. Warm blood running through arteries from the heart distributes body heat. By the time it reaches an animal’s extremities, it has cooled and not much body heat can be lost. Reindeer have countercurrent vascular systems where veins containing cool blood returning to the body’s core run adjacent to arteries with warm blood. The colder veins absorb heat so the body core stays warmer.

Arctic fox staying warm by Marc Dumont, Feb 2015

Polar bear portrait by Peter Kaminski, Jan 2005

Extremities are one body area where heat is easily lost and exposure to cold can be damaging or deadly. Arctic foxes and arctic hares have shorter ears, noses, limbs, and snouts than species in the same families living in temperate weather zones. Ringed seals lack any external ears. Musk oxen have short legs and tiny ears, as do polar bears. Many of these adaptations can be viewed in the wild, or at your local zoo. Natural history museums also have displays where we can learn about many cold-adapted species.