Archives For Ecology & Wildlife

The Chicago Botanic Garden is actively maintaining, restoring, and recreating four natural areas at the Garden: woodlands at McDonald Woods and the Brown Nature Reserve, the Dixon Prairie, the Skokie River Corridor, and the 60-acre Garden Lakes. These activities teach restoration ecologists a great deal about habitat management, which can be applied in other regions.

Want to help monarch butterflies? Be careful when selecting your milkweed. Not all plants that go by the common name of “milkweed” are the food that these butterflies need. 

Want to save the monarch butterfly? Plant milkweed. Pick up a free milkweed seedling at World Environment Day this Saturday, June 4.

Danaus plexippus (Monarch) egg on the underside of a leaf.

Danaus plexippus (Monarch) egg on the underside of a leaf. Photo by Bfpage [CC BY-SA 4.0], via Wikimedia Commons

Milkweed is both a food source and a host plant on which the monarch butterflies lay their eggs. Monarchs lay their eggs on the underside of the milkweed foliage.

After hatching, the larvae consume the foliage, which is high in cardiac glycosides—a poison that interferes with the heart functioning of vertebrates (animals with a skeleton). Butterflies are insects with an exoskeleton, and so are not affected by the toxin.

Within the Chicago region, the following milkweed species (Asclepias) are native:

  • Asclepias amplexicaulis is native to our prairies and is suitable for planting in sunny perennial flower gardens. The flowers are described as “eraser pink” in color and are fragrant (honey).
  • Asclepias exaltata is native to our woodlands and is suitable for planting in partially shaded gardens. The flowers are white and also fragrant.
  • Asclepias incarnata is native to both prairie and woodlands and can be planted in a variety of garden locations. The flowers are pink and fragrant. Gardeners may also be interested in three cultivars of this species:
    • ‘Cinderella’ has light and medium pink flowers
    • ‘Ice Ballet’ has white flowers
    • ‘Soulmate’ has medium and dark pink flowers
  • Asclepias tuberosa goes by the common name of Butterfly Weed. It features bright gold and orange flowers—and is fragrant. A native of sunny prairies, it also has cultivars that have been selected for specific colors:
    • ‘Hello Yellow’
    • ‘Western Gold Mix’
    • ‘Gay Butterflies’ (orange, red, yellow)
  • Asclepias purpurascens has fragrant pinkish-purple flowers and can tolerate both sun and shade locations in the home landscape.

Cultivars may be easier to find in your local garden center or nursery, but specialist nurseries do carry both potted plants as well as seeds.

Asclepias syriaca

Asclepias syriaca

Asclepias tuberosa

Asclepias tuberosa

Download the Chicago Botanic Garden Milkweed Map and take a tour of our native milkweeds.

The Bad Seeds

The bad actors, unfortunately, also go by the common name of milkweed, and are in the same plant family but a different genus: Cynanchum. Three species are reported in the upper Midwest and should not be planted by gardeners. All have fragrant flowers and wind-dispersed seeds:

  • Cynanchum louiseae goes by the name of Louise’s swallow wort, or milkweed. It is native to southeastern Europe.
  • Cynanchum louiseae goes by the name of European swallow wort or milkweed. It is native to southern Europe.
  • Cynanchum vincetoxicum goes by the name of white swallow wort or milkweed. It is native to Europe and Asia.

So, why will monarch larvae die on the wrong milkweed? 

Hmmm, perhaps an illustration. Both mango and poison ivy are in the same plant family (Anacardiaceae) and contain similar biologically active compounds. My daughter and I can’t get enough mango in our diet, but both break out in poison ivy rashes if we touch poison ivy plants. The compounds are similar but not exactly the same.

Likewise with the “bad” and “good” milkweeds: Both have fragrant flowers, the flower shapes are similar, the leaf shapes are similar, both have milky sap. But there is an insecticide compound in the “bad” milkweed in addition to the cardiac glycoside.

“Bad” milkweeds evolved in Europe, where there are no native monarch butterflies, but plenty of herbivores, both animal and insect. “Good” milkweeds evolved in North America in conjunction with monarch butterflies.

Monarch caterpillar

Monarch caterpillar

Somehow, the monarch larvae are able to ingest and retain cardiac glycosides in their tissues without dying. It is a very unique adaptation between these two species. If other species of butterflies were to lay their eggs on milkweed, the larvae would not survive. Each organism has these sorts of “monarch-like” relationships with other, sometimes drastically different organisms that give them a survival advantage. Monarchs just happen to be a wonderful example of mutualistic relationships.

Learn more:

The Monarch Joint Venture lists a number of national and regional partners; each of them will have information about monarch butterflies. The U.S. Fish and Wildlife Service, which is partnering with the National Wildlife Federation and National Fish and Wildlife Foundation, is also a source for information on milkweed and monarchs. Get free milkweed plants at monarchwatch.org.

Million Pollinator Garden Challenge

Add your garden to the Million Pollinator Gardens project this summer. Learn more at millionpollinatorgardens.org.


©2016 Chicago Botanic Garden and my.chicagobotanic.org

While working out in the woods this winter, a small lump on the branch of a young elm tree caught my attention. At first I thought it might be a gall, or an injury that had healed-over. On closer inspection, the lump turned out to be a ruby-throated hummingbird nest from last summer. 

Although I see hummingbirds regularly at the Chicago Botanic Garden, I rarely encounter one of their nests. Hummingbirds themselves are amazing, but their nests are truly a marvel of avian architecture. Not much larger in diameter than a quarter, they are just large enough to hold the one to three navy bean-sized eggs of the hummer. For the pint-sized bird to be able to keep the tiny eggs warm during incubation requires that the nest be not much larger than her body. 

PHOTO: Hummingbird nest and quarter (for scale).

Not much larger than a quarter, the ruby-throated hummingbird nest is an engineering marvel.

This is all well and good until the eggs hatch. Growing young hummingbirds can double or triple the amount of room necessary to hold the family. One of the ways the hummingbirds get around this need for flexibility is that they construct the nest of soft plant fibers and then wrap the whole thing with spiderweb silk. This creates an elastic nest that has the ability to expand as the contents of the nest increases. Can you imagine yourself going out and plucking a strand of sticky silk from a spider web with your fingers and then trying to use it to build something out of lightweight fuzzy plant fibers? I imagine you might find yourself wrapped up in a ball like some sort of oversized grotesque moth cocoon. The silk also helps to anchor the nest to the top surface of a horizontal branch.

PHOTO: Spiderweb silk is used by hummingbirds as a nest liner.

Spiderweb silk: the expandable nest liner preferred by hummingbirds.

Keeping the nest just the right size as the need arises helps to keep the growing youngsters warm and secure. In the western states where several species of hummingbirds nest, often at higher elevations, it is not only important to keep the nestlings warm, but also the incubating female, especially at night. Therefore, it is often the case that hummingbirds in these colder situations will locate their nests on a limb with an overhanging branch acting as a sort of roof to help block the nest from the night sky. 

Although this measure helps reduce heat loss, it is often the case that nesting females will go into a state of torpor (reduced physiological activity to lower body temperature) in order to conserve energy on particularly cold nights. This is a principle of physics in which the larger the difference in temperature between objects, the faster the heat flows from the warmer one to the cooler one. Therefore, a hummingbird with a lower body temperature will lose heat more slowly than the one with a warmer body. As I stated earlier, hummingbirds are amazing!

PHOTO: Parmelia sulcata, a common lichen, is used to help disguise the hummingbird's nest.

Parmelia sulcata, a common lichen, is used to help disguise the hummingbird’s nest.

Part of the reason—besides size—I had not noticed the nest earlier is that the birds do a fantastic job of camouflaging it. This also relates to the spiderweb silk. Some or all of the silk used is sticky. Upon completion of nest construction, the birds collect bits of lichen and attach them to the sticky strands on the outside of the nest. Interestingly, the birds seem to always use the same species of lichen, one that goes by the name of Parmelia sulcata

Parmelia sulcata is a light greenish-gray lichen with a leafy (foliose) appearance. One of our more common lichens, it is often seen on the upper branches of trees, and was particularly abundant on the ash trees that died from emerald ash borer. I don’t know if the birds chose this species of lichen in particular or, being common, it is just found most often. It is also interesting that the birds seem to apply the lichens to the nest in an upright position, with the top facing outward, so they look like they could be growing on the nest.

Come birding at the Garden! Take a birding class; join a group, and check your finds against our bird list.

Although this process is fascinating, it is not restricted to hummingbirds. One of the other breeding birds at the Garden utilizes a very similar nest construction technique to hold its three to five small eggs. The blue-gray gnatcatcher, another tiny bird (that somewhat resembles a miniature catbird in appearance and sound), also constructs a nest out of soft plant fibers, including spiderwebs, and applies lichen to the outside of its nest. A nest of this species, a little larger than that of a hummingbird, was found on a branch of one of the locust trees growing in a Garden parking lot.

PHOTO: A female ruby-throated hummingbird (males have the ruby coloring) enjoys a sip of salvia nectar in Circle Garden in summer.

A female ruby-throated hummingbird (males have the ruby coloring) enjoys a sip of salvia nectar in Circle Garden in summer.

PHOTO: A blue-gray gnatcatcher at the Garden; females look similar, but are less blue.

A blue-gray gnatcatcher at the Garden; females look similar, but are less blue.

If you’re lucky, you might find the nest of one of these birds during the nesting season, but if not, keep an eye out for little bumps, lumps, and knobs on bare branches in winter. You might get lucky.

Come #birdthepreserves with the Forest Preserves of Cook County. View our list of upcoming events for free events near you.


©2016 Chicago Botanic Garden and my.chicagobotanic.org

Do you see something pushing up from the ground that looks like the claws of some creature in a zombie movie? Does it smell bad too?

Happy spring! This charmer is the first native wildflower of a Chicago spring: the skunk cabbage (Symplocarpus foetidus).

PHOTO: A skunk cabbage blooms in early March in the McDonald Woods.

A skunk cabbage blooms in early March in the McDonald Woods.

It’s a biologically intriguing, ecologically brilliant prelude to the wildflower riot about to burst forth on forest floors from the McDonald Woods at the Chicago Botanic Garden to area preserves.

It’s a welcome sight to Boyce Tankersley, the Garden’s director of living plant documentation, who pointed out skunk cabbage as we walked through the McDonald Woods, the 100-acre restored and protected natural area that is home to at least seven state-listed threatened or endangered plant species.

Skunk cabbage’s appearance means that the trilliums and bloodroot are not far behind. And spring beauties, star-flowered isopyrum, and cardamine, also called bittercress. Within a few weeks, depending on the weather, forest floors will be carpeted with wildflowers, courtesy of the sun streaming onto the earth before the trees leaf out and block it.

Skunk cabbage isn’t conventionally pretty. What you see are the claw-like pointed red-striated hoods called spathes surrounding a nub studded with blossoms. The plant creates its own heat, even amid snow and ice. The temperature inside the hood can be 95 degrees hotter than outside.

Thermogenesis is the goal for skunk cabbages, titan arums, and other “warm-blooded” plants.

The heat creates the plant’s signature smell, a cross between a skunk (hence the name) and rotting meat. This turns skunk cabbage into a paradise for flies, which seek out rotting meat where they can lay their eggs.

“It’s kind of got the rotten vegetation look going on,” Tankersley said. “It’s warm, which means there’s something decomposing, from a fly’s perspective. And then of course it smells bad. So there’s your triple play: ‘You need to come here.’”

And flies do come to skunk cabbage. They flit inside the hood looking for rotting meat, then emerge covered with pollen. Then they fly inside another skunk cabbage, and pollinate it.

Honeybees are the plant’s other major pollinator. They are attracted to skunk cabbage because it is a rare, early source of pollen, on which they feed. You can see a honeybee in pollen-coated action inside a skunk cabbage in the video below by the Illinois Natural History Survey: 

Watch the Skunk cabbage video on YouTube.

Skunk cabbage is picky about where it grows. You can only find it in fens, wet woodlands, and other places where water is moving beneath the soil’s surface. At the Garden, they’re alongside the path through the McDonald Woods. Outside the Garden, a good spot is the River Trail Nature Center, a Cook County forest preserve in Northbrook.

And while you can see skunk cabbage now, the other wildflowers are still holding back. That’s because they’re smart.

“They’ve seen these warm temperatures and then had the weather snap on them,” Tankersley said. “Genetically, they know if they hope to survive, they can’t come out with the first warm weather.”

Which is why native wildflowers are almost never felled by a sudden freeze.

PHOTO: Prairie trillium (Trillium recurvatum).

The elegant—and less smelly— prairie trillium (Trillium recurvatum) is our next bloom to look for in the woods. Keep an eye out!

In the next weeks, the wildflower show will be on in full force. In addition to the McDonald Woods, you can catch it at forest preserves, where invasive species like buckthorn and garlic mustard are regularly removed, as they are at the McDonald Woods. Some of my Forest Preserves of Cook County favorites not far from the Garden are Harms Woods near Glenview and LaBagh Woods near Cicero and Foster Avenues on the city’s Northwest Side.

But the previews are open now. And it’s a real stinker.


©2016 Chicago Botanic Garden and my.chicagobotanic.org

If You Can’t Take the Heat, Stay Out of the Fire

Burning prairies wisely saves animal and invertebrate life, while regenerating the plant landscape.

Jim Steffen —  March 10, 2016 — 2 Comments

This winter has been unpredictable with unusually warm weather one day and biting cold the next. During one of those particularly cold periods in January, I took advantage of the solid ice to work on removing woody invasive plants from one of our isolated wetlands in the McDonald Woods.

We have several such wetlands, but this one is perhaps more interesting than the others, in that it is home to a population of broad-winged skippers (Poanes viator)—an uncommon butterfly that has only been found on six or fewer sites being monitored for butterflies in the Chicago region.

PHOTO: Broad-winged skipper (Poanes viator).

Broad-winged skipper (Poanes viator)

This small brown butterfly is dependent on lake sedge (Carex lacustris) as a larval food plant on our site. It has been found to feed on some other sedge and grass species elsewhere, but here, that is the only plant that its larvae feed on.

In the 26 years I have been managing the 100 acres of the McDonald Woods, this small quarter-acre wetland is the only spot this butterfly can be found. Although there are many patches of lake sedge found throughout the woodland, apparently this butterfly will not leave this small and sunny wetland to venture into the surrounding shade of the oak canopy to take advantage of the other sedge patches.

PHOTO: Lake sedge in winter.

Lake sedge in winter

As I was working among the dormant lake sedge stems—solidly anchored in the thick ice of the wetland—I decided to do a little investigating to see if I could find any clues to the whereabouts of this butterfly in winter. Some butterfly experts think this skipper overwinters as a developing larva, then later pupating before emerging as an adult in early July. However, it seems as though no one is quite sure where exactly the developing larvae would be found.

PHOTO: Broad-winged skipper larva.

Possible Dion skipper larva

As I was working in the wetland, I occasionally plucked a dried-up stem of lake sedge and peeled the leaves back, much as you would peel a banana. Although I did not find a broad-winged skipper larva, I did find the larva of a noctuid moth, what appears to be the larva of a Dion skipper (Euphyes dion), some various fly larvae, a couple tiny adult flies, hundreds of sac spiders (Clubiona maritima), some Linyphiid spiders, Gnaphosid spiders, and a few other spider genera. Although I am well aware that many invertebrates spend their dormant periods hidden away in stems, leaves, and roots of plants, I was amazed to see how much life was present in the dried stems above a solid block of ice.

This revelation got me thinking about my management activities, and in particular, the use of controlled burning. Much like prairies, oak woodlands are dependent on fire to prevent fire-intolerant woody plants from moving in and creating too much shade for the “sun loving” oak trees to reproduce themselves.  

Prairies and oak woodlands evolved primarily as a result of climate, and in particular, rainfall. As you travel eastward from the Rocky Mountains, you first encounter short grass prairie where the rainfall is lowest, then mixed-grass prairie where it is a little wetter, then tall grass prairie where it is still wetter, then oak woodlands and eventually, eastern deciduous forest, dominated primarily by fire-intolerant tree species (like maple and beech), where the rainfall is most abundant.

PHOTO: Euphyes dion by Charles T. and John R. Bryson, Bugwood.org.

Euphyes dion by Charles T. and John R. Bryson, Bugwood.org

These prairies and oak woodlands provided a readily burnable fuel for any fire that got started, whether as a result of intentionally set fires by Native Americans or random lightning strikes. It is not hard to picture the description of early settlers when they wrote about fires that burned for days and covered hundreds of thousands of acres. As the prairie fire approached oak woodlands, they did not go out but continued to burn through the flammable leaf litter and dry herbaceous plants covering the ground of these woodlands.

But historically, these were huge landscapes. Today we are dealing primarily with tiny fragments of the plant communities that once covered thousands—if not millions—of acres. Because the landscape has changed and these remnants are now so small, they no longer experience the landscape-scale fires in which some areas burned while others did not. Back then, when habitats were huge and animal populations were large and widespread, these fires helped to maintain rich and diverse habitats and animal populations for thousands of years. It is always impressive, even after a single fire, to see the abundance of native seedlings emerge from the burned understory and later, the increased flowering of mature plants. But we don’t always consider the unseen other life forms hidden among the dried leaves and stems. Therefore, as managers, it is important that we utilize fire in a thoughtful way to try to restore and maintain all the richness in what remain of these once extensive natural systems.

Getting back to my experience in the winter wetland, there is a tremendous amount of invertebrate life that is present in the dry and burnable plant material in these dormant plant communities. This is particularly important when the entire population of a single species, like the broad-winged skipper, is found in such a restricted space. Plants and animals found in prairies and oak woodlands have evolved adaptations to periodic fires.

PHOTO: The Dixon Prairie in full bloom.

The Dixon Prairie in full bloom

Research has shown that most invertebrates are able to rebound after fire, but as managers, it is important that we make an effort to give these species the best opportunity to flourish on our small remnants. We can best do this by scheduling our burns—not burning the entire patch of any one particular habitat at any one time, especially during extreme weather conditions. And we should always try to leave some remnant vegetation unburned so that populations can regenerate themselves from those individuals that remain. Fire is an extremely important management tool for restoring and maintaining these natural communities, but it must be used wisely.


Photos @ Jim Steffen except where noted.
©2016 Chicago Botanic Garden and my.chicagobotanic.org

Look up! In partnership with Friends of the Chicago River (FOCR) and the Forest Preserves of Cook County (FPCC), an osprey nesting platform was installed on Friday, January 29, along the North Branch Trail at the south end of the Chicago Botanic Garden near Dundee Road.

MAP

The Garden’s new osprey nesting platform is located near Dundee Road and is viewable from the North Branch Trail.

The osprey is listed as an endangered species in Illinois, which means it’s at risk of disappearing as a breeding species. Fish-eating raptors that migrate south and winter from the southern United States to South America, osprey are often seen during their migrations—yet few remain in Illinois to nest. The lack of suitable nesting structures has been identified as a limiting factor to their breeding success here.

Males attract their mates to their strategically chosen nesting location in the spring. In order for a nest to be successful, it must be located near water (their diet consists exclusively of fish, with largemouth bass and perch among their favorites), the nest must be higher than any other nearby structure, and it must be resistant to predators (think raccoons) climbing the nest pole and attacking the young.

FOCR and the FPCC sought out the Garden as a partner for an installation site, in large part owing to the Garden’s strong conservation messaging and proximity to other nearby nesting platforms that have been recently installed (two are located alongside the FPCC’s Skokie Lagoons just to the south).

The Garden’s nesting platform was installed atop an 80-foot “telephone pole,” set 10 feet into the ground and extending upwards by 70 feet. The 40-inch hexagonal nest platform atop the pole has a wire mesh on the bottom so that water can pass through the sticks and stems that the osprey will bring to construct the nest.

PHOTO: Installing and osprey nesting pole.

A truck-mounted auger and crane set the nesting pole and platform into place.

PHOTO: Installing an osprey nesting pole.

The nesting platform sits atop the pole and is ideally sized for a future osprey nest; notice that we even “staged” the new osprey home with a few sticks of our own!

PHOTO: Installing an osprey nesting pole.

A metal band was wrapped near the bottom of the pole to prevent predators from being able to climb it.

PHOTO: Installing an osprey nesting pole.

The nesting pole and platform is fully installed and is visible from the North Branch Trail that runs through the Garden.

With the osprey nesting platform now in place, our hope is that within the next few years, a migrating male will select the site and pair with a female. Osprey generally mate for life, though they’re together only during the breeding and rearing seasons.

You can learn more about the how and why of the osprey nesting platform project at the FOCR website. Follow the links on that webpage for images, video, and a press release relating to the installation of an identical osprey platform at the Skokie Lagoons last spring.

Read more about the long-term effort, and about ospreys making a comeback in Cook County. Discover birding at the Garden and find our full bird list online at chicagobotanic.org/birds.


©2016 Chicago Botanic Garden and my.chicagobotanic.org