The Autumn Show

Autumn is finally settling in the St. Louis area; the overnight chill lingers a little longer in the morning, the hours of daylight are decreasing, and the leaves are finally turning colors.

Have you ever wondered what causes the leaves to turn those brilliant shades of red, orange and yellow, and why it seems that the autumn foliage is more colorful some years than others?

Let’s begin with the leaf.

The carotenoids, the pigment responsible for the fall colors, is already present with in the leaf but is concealed by the green color of chlorophyll, the component essential for photosynthesis. The base of each leaf contains a special layer of cells, known as the separation layer, where the exchange of water and food between the leaf and tree takes place.

The leaves are responsible for providing food for the tree and it performs this duty through photosynthesis. In photosynthesis, the leaves use water and carbon dioxide to produce carbohydrates for the tree and oxygen is the by-product of this process. On any given day, the average tree will take in 1-1/2 pounds of carbon dioxide and release about a pound of oxygen into the atmosphere. The leaves also produce more food than is needed and the tree will convert the excess sugar into starch to consume during the winter months.

The shorter hours of daylight and cooler temperatures trigger a reaction that allows the leaves to reveal their autumn colors. During this time, the cells within the separation layer form a cork-like material that cuts the exchange of water and glucose from the leaf. The chlorophyll within the leaf disappears when the water supply is cut off, revealing the hidden oranges, reds or yellows.

The orange leaves are produced from carotene pigments,

yellow leaves are a result of xanthophyll pigments

and anthocyanin create the red and purple leaves.

Interestingly enough, not all trees produce anthocyanin and this pigment is only made during the fall months.

Contrary to popular belief, rainfall is not the only factor responsible for the colors of autumn. Sunlight, cloud cover, temperature and soil acidity also determine the intensity and duration of fall’s colorful show. For example, bright light produces anthocyanin. The brighter the sunlight, the more vivid the red and purple leaves. A warm wet spring followed by a summer that is neither too hot nor too dry that leads into a fall with warm sunny days and cool nights will produce a dazzling leaf display.

Now that you know the work the leaves put into their visual displays, I hope you get a chance to go outside and enjoy Autumn’s show.

Mist Netting 101

I have been mist netting for about 13  years now and when I talk about it, I'm often asked "How do you catch the birds?" or "What is mist netting?" and "Why do you do it?"

I find the process of mist netting difficult to explain without photographs. Of course it's best to demonstrate it in person, but that's usually not possible. So, without further ado...here is your crash course in mist netting.

"Mist nets" are nylon or polyester nets that vary in length. The net mesh also varies in width and length. Depending on location, the nets can be fairly easy to see, as in this picture.

Or, nearly invisible.

A bird will fly into the net

Red-eyed Vireo

Author removing a bird.

Extracting a bird.

Once the bird is removed from the net, a lightweight band made of aluminum or stainless steel is placed on its leg, wing and tail measurements are taken, the overall health of the bird is assessed, and  the age and sex of the bird is determined if it's possible.

Banding a Winter Wren.

Yellow-billed Cuckoo. Note the band in the lower center of the picture.

Processing a Veery with the aid of a technical book.

Examining the wing coverts of a Swamp Sparrow.

Banding is essential for field ornithologists in tracking migrating raptors and songbirds,

population growth or decline and reproduction success. Bird banding is done worldwide, but specifically here in the United States, all banders order their bands from the Dept of the Interior and report their data to the Patuxent Bird Banding Lab. If a banded bird is captured in a different location, the person who caught the bird will submit their findings to the Bird Lab who in turn, notifies both parties, thus tracking the migration habit of that particular bird.

Gray-cheeked Thrush. Because of banding, we know these birds migrate through St. Louis in the spring and fall.

On a local level, bird banding is especially helpful in monitoring the birds that return to the same site each year.

This Indigo Bunting was banded in 2008 and later recaptured at the same site in 2012

Over 63,000,000 birds have been banded since the beginning of the program in 1902 and 3,500,000 have been recovered and reported to the banding offices. As I stated earlier, banding birds is also a good way to keep track of the nesting success and the longevity of our avian friends. The Bird Banding Lab has compiled a list of the longest lived birds based on submitted band information. Here is the link.
Mist netting is a wonderful opportunity to examine the variety of colors and textures in the feathers of the birds. A bird that looks drab from afar may have several shades of brown and minute stripes and speckles not seen through a pair of binoculars. Often I have discovered tiny bristles around a beak, a shade of yellow hidden under the wings or beautiful chestnut colored eyes on a bird in my hand. Things I may not ordinarily see on that bird while it is hopping around in a sycamore tree or miss because the lighting washed out the colors.

Mist netting and handling the birds has also helped improve my bird watching skills because in constant handling of the birds, you notice the overall shape of the bird, proportion of wing and tail length and yes, those feather colors and arrangement of colors. And more importantly, mist netting has enhanced my respect and admiration of these tiny creatures.

Adventure at my feet

I went for an afternoon walk at the Riverlands Migratory Bird Sanctuary yesterday. With binoculars and camera in tow, I looked at a pair of American Kestrels, a handful of Song Sparrows, and photographed a myriad of dried flowers. While walking through the vegetation, a flurry of movement at knee level caught my eye. I knelt down to find a Banded Argiope (Argiope trifasciata) wrapping up a grasshopper in her web.

Banded Argiope and prey

Mesmerized, I watched her for several minutes rotate around the grasshopper, leaving silk in her wake.

Spider wrapping grasshopper. Note the spider's spinnerets.

Spider silk is a protein produced in liquid form by special glands within the abdomen. The silk leaves the body through the spinnerets located at the end of the spider's abdomen. Once the silk leaves the body, it is transformed into dry fibers. Spiders can can manipulate the thickness, strength, and elasticity of their silk.

The Banded Argiope is a member of the Orb Weaver Family Araneidae and can be found throughout Missouri in tall grasslands and open areas with sparse brush.

You never know what you'll find during a walk in the park. I felt lucky to have this encounter with nature.

Preparing For Winter

With the arrival of Autumn Equinox last weekend, the hours of daylight will continue to shorten and the nights grow long until the Winter Solstice. On the surface, life seems to be slowing down on the prairie, but in reality, the plants and animals are busy preparing for the upcoming cold months.

Mantid Ootheca

Last week I found a Chinese Praying Mantis (Tenodera sinensis) ootheca, or egg case. A female mantis will choose a weed or other sturdy plant stem about 4 feet off the ground and begin the process of laying the ootheca and eggs. The eggs are usually arranged in rows near the plant stem, and on either side of the eggs, the female mantis lays a frothy, brown material filled with air. Initially this protective material is sticky and soft, but when it dries, this outer part of the case will be hard and water repellant. The female begins laying ootheca in August and can leave as many as 15 egg cases before she dies. Each ootheca can have up to 400 eggs. The eggs will survive the winter months within the ootheca and the nymphs hatch in late spring or early summer. These tiny mantids disperse on the wind and will molt up to 7 times before they reach adulthood.

There was one woolly bear caterpillar looking for food in the prairie. This fuzzy caterpillar is one of the many tiger moth species that belong in the Arctiidae family. These active caterpillars are covered in short, dense hairs and are always on the move searching for food and a safe place to overwinter.

Woolly Bear caterpillar

Monarch Butterfly on Goldenrod

Monarch migration has begun. Each fall, these butterflies fly to Mexico for the winter. The Monarchs that emerge in late summer to early fall are the ones that make the trip. This generation of Monarchs will not mate or lay eggs, rather they prepare for the long trip south. They need to store enough fat to travel and survive the winter months. This is an area of interest for scientists, as it is not known exactly how these butterflies store enough energy to survive such a difficult journey and live until spring. Amazingly, these same butterflies will migrate up north once spring arrives to reproduce.

There are a few hundred American Goldfinches feeding on the seed heads in the prairie and it appears that the young Goldfinches have mastered the art of foraging.

American Goldfinch

Illinois Bundleflower

The plants at the Ecology Center have gone to seed. This means that the plant uses its energy for creating seeds instead of growing. The seed head on this Illinois Bundleflower (Desmanthus illinoensis) is dried and ready to be dispersed. Illinois Bundleflower is an important food source for animals and botanists often use this plant when creating a restored prairie.

Ohio Buckeye

The seed pods from the Ohio Buckeye (Aesculus glabra) trees bordering the prairie have matured and are dropping to the ground. These seeds are covered by a rough, warty pod, and each capsule can house up to 3 seeds. Ohio Buckeyes prefer moist habitat, and can be found along streambanks and river bottoms. The seeds contain tannic acid and are poisonous to humans and livestock, but constitute a small percentage in the diets of squirrels and deer.

Stay tuned for next month's natural events!

Glossary

Cocoon: a silk web that encloses the pupae of many moths, but not butterflies. 

Forage: the act of searching for food.

Molt: the act of shedding skin. A monarch larva will molt its skin as it becomes too large for its former skin.

Nymph: Immature stage of an insect with simple metamorphosis

Ootheca: An ootheca (plural oothecae) is an egg mass produced by several different groups of insects, including Praying Mantids and Cockroaches. Oothecae contain many eggs with a protective outer covering.

Overwinter: to remain alive throughout the winter.

Pupate: to change from a larva (caterpillar) to a pupa (cocoon or chrysalis)

Fall Seeds

Autumn is a busy time at the Ecology Center with the staff collecting and cleaning seeds for planting in the spring. Before we discuss the process of collecting and cleaning, let's talk a little about seeds in general.

Annenberg Learner http://www.learner.org/courses/essential/life/

After a plant is fertilized, the egg cell divides many times to form the embryo, or the baby plant. The plant embryo forms a hard wall around itself and this is known as a seed coat. Within the seed is the endosperm, which provides food to the developing embryo. The cotyledons within the seed provide a similar function. These are the seed leaves and they also contain food for the developing plant. The seed coat houses the embryo and is able to withstand extreme temperatures, fire, snow and ice, abundant rainfall or dry spells. The seed coat also protects the embryo from abrasive material found in the soil, and passage through the digestive system of animal.


A newly formed seed may require days, weeks, months, or even years to fully mature and requires the correct soil temperature, moisture, humidity and length of daylight to germinate.

Although some plants drop seeds at their bases, most are dispersed through a variety of methods. Some seeds are designed to be lifted and carried on the wind; Maple trees, Milkweeds and Thistles take advantage of the wind.

Swamp Milkweed seeds are dispersed on the wind.

There are other seeds with barbs, bristles, tiny hooks and hairs that latch on to the fur of a passing animal or human clothing. Beggar's ticks (Bidens sp), Cockleburs, and Burdock (Arctium lappa) are a few examples of these sticky seeds.

Seeds attached to the author's pants.

Some animals, such as birds, eat seeds which are later distributed after the animal defecates. Some of these tasty seeds include Poison Ivy, Mulberries, Pokeweed and Japanese Honeysuckle.

Goldfinches love (and disperse) Purple Coneflower seeds

Seed cleaning may bring images to mind of scrubbing seeds with soap and water, but this is not the case. Seed cleaning is essentially separating the seeds from the chaff and spreading them out to dry. Ideally, colanders, sieves, window screens or other forms of metal screens are ideal for this step, but space and cost is something of an issue for us. We (or willing students) separate the seeds from the chaff on top of a white piece of paper or tray before moving the seed to another tray.

The newly separated seeds can be dried in paper or plastic bags (open for air circulation), dixie cups or spread out on small plates. The seeds need to be turned or stirred every few days to make sure they are dried evenly. Once dried, the seeds can be stored in a cool place (usually the refrigerator) out of direct sunlight until they are ready to be planted.

Glossary

Chaff: the outer material on a plant, such as the seed coat, dried flowers, leaves and other scaly material.

Germination: the process in which an inactive seed begins to sprout and grow into a seedling under the right conditions.

 

The Late Bloomers

For the first time last week, I began to hear the familiar begging calls of young American Goldfinches. I peeked outside and sure enough, there were 3 hatch year Goldfinches on my patio hopping around, pecking at leaves and exploring the covered BBQ pit. One of the goldfinches hopped under the BBQ pit, another one perched on a flower pot, and the last goldfinch started to fly towards the BBQ pit. I think he was trying to reach the top of the pit, but his takeoff was too close, so he settled for the side instead.

A hatch year Goldfinch looks very different from his or her parents. In that same turn, male and female goldfinches also look different from each other. This difference in the feather colors between males and females is known as sexual dimorphism. During the summer, male goldfinches are bright yellow with a black head and wings. The females are a muted yellow, and lack the black head.

The young goldfinches were in various stages of learning to feed themselves. One little goldfinch begged his sibling for food...while on the bird feeder. But there was another young goldfinch that was beginning to master the art of foraging. This little one was plucking seeds off my Purple Coneflowers (Echinacea purepurea) in the backyard.

American Goldfinches nest later than other songbirds. Most birds breed late April through mid June but the goldfinches begin breeding in late June through July. These birds breed when milkweed, thistle and other plants have produced their fibrous seeds. The female builds the nest, usually in a shrub or sapling in a fairly open setting rather than within a forest. The nest is often built high in a shrub, where two or three vertical branches join; usually shaded by leaves of clusters of needles from above, but often open and visible from below. The nest is an open cup of plant fibers and rootlets and the interior is lined with the fluffy material surrounding the seed from thistle and other plants. The nest is so tightly woven that it can hold water. 

Goldfinches are seed eaters, even during the breeding season. While most seed eaters, such as Sparrows, switch to an insect diet during the summer months, the goldfinches continue their seed eating diet and feed their young the seeds from trees, flowers, and shrubs.

 

You can find American Golfinches in parks, weedy fields, pastures, grasslands and in fields containing mature sunflowers. They will also eat from bird feeders that offer sunflower and thistle.

You may think that the bright yellow colors of the American Goldfinch really stand out - and indeed they do in a backyard while perched on a bird feeder. But out in a field of flowers, they are well camouflaged. Can you find the Goldfinch in this picture?

Be on the lookout for our pretty yellow feathered friends. If you are around a small field of, or even a cluster of dried flowers, the Goldfinches are sure to be nearby. 

Glossary

Hatch Year: A bird that has hatched during the spring or summer. A young bird will be considered a hatch year bird until January 1st, when all are then considered adult birds.

Camouflage: The colors and markings of an animal or bird that allow it to blend in with its surroundings so as not to be detected by predators.

Summer's Last Hurrah

September is already upon us and summer is winding down to a close. The days are gradually getting shorter and the birds that spend their summers in St. Louis are beginning to migrate to their winter homes. Generally speaking in terms of migration, male birds are usually the first to leave, with females and young birds following suit.

There are still a few summer birds on the prairie, but most of them have left. An Indigo Bunting fussed at me as I walked.

It is difficult to determine if this is a female or a young Bunting. Adult male Indigo Buntings are a rich blue color, while their female and young counterparts are brown.

The American Goldfinches are abundant on the prairie right now.

They are busy eating the seeds from the Coneflowers, Cup Plants and the myriad of other flowering plants living on the prairie.

The bees are busier than ever collecting pollen, the cicadas are singing in the trees, butterflies flit from flower to flower and dragonflies dance across the sky.

A dragonfly can spend up to 5 years of its life as a nymph. The nymph form looks completely different from the adult form and lives in a completely different habitat - water. While the adult dragonfly is flying in the air, the nymph is developing underwater. Both the nymph and adult dragonflies eat mosquitoes, midges and other small bothersome insects.

The prairie is awash in yellow right now.

Sweet Coneflower (Rudbeckia subtomentosa) are the beautiful flowers responsible for the prairie's sunny color.

These moist-loving plants can be found in prairies, savannahs, thickets, floodplain forests, woodland borders, roadside ditches and riverbanks. Bloom time begins in July and lasts all the way through late fall.

Ironweed is also in bloom right now. Ironweed is in the asteraceae (daisy) family and there are many species of this plant in Missouri.

Ironweed can tolerate both wet and dry habitats and is found in prairies, meadows, fields, glades, dry woodland and along railroad tracks. They grow  3 - 5 feet in height and bloom July - September. The name Ironweed refers to the tough stems that are often difficult to dig up, and the flowers producing rust colored seeds. This plant is sometimes thought of as a weed because of its propensity to grow abundantly in fields and pastures.

Life may seem to be slowing down on the prairie, but this habitat is active year round. We'll see what is happening on the prairie next month.

An Overview of the Arachnids: Spiders, part one.

What is your reaction when you hear the word “spider”? Do you get a shiver down your spine? Do you feel fear or admiration?  There are often mixed reactions to spiders with movies and the media adding to the misunderstanding of our arachnid friends. The point to this entry is to educate readers on the natural history of spiders. You may still not enjoy being around  spiders after reading this blog entry, but perhaps you will take pause and decide not to kill that 8 legged critter scurrying up the wall. 

Spiders are not insects. They belong in the Arachnida class along with ticks, mites, harvestmen (daddy long legs) and scorpions.  There are about 40,000 known spider species. This is an impressive number, considering there are only 4,000 species in the mammal kingdom.   Missouri boasts 480 species of spiders.

Common Missouri Spider by Nancy Zuschlag. MDC Publication

Arachnids have 8 legs and two body parts, a cephalothorax (a fused head and thorax) and an abdomen.  Spiders have 8 eyes that are grouped in 4 pairs and despite all of those eyes, their sight is poor. To compensate for their poor eyesight, the body of a spider is covered in very sensitive hairs that pick up vibrations in their surroundings and the air.  

Spiders have fang-tipped jaws called chelicerae. They use these fangs to inject venom into their prey and to tear food apart before eating. Pedipalps, the limbs (they closely resemble the spider’s legs, but are smaller) in front of the fangs are used for reproduction, grabbing and killing their prey.  Arachnologists (scientists who study spiders) believe these limbs may also have a function similar to antennae. 

The abdomen contains the heart, lungs, digestive tube and spinnerets. The spinnerets, found at the back of the abdomen, produce silk. Spiders use this silk to create webs to trap prey, use as safety lines during climbing, building homes, mating, and egg sacs for their developing offspring. Incidentally, those newly emerged spiders release silk that catches in the wind and carries them to their new home.

Female Wolf Spider with eggs

 

Spider eggs enclosed in silk.

Believe it or not, those 8 legs of the spider have their functions as well. Arachnids can hear, feel and even smell with those legs. Their feet contain tiny claws that allow them to walk on their webs, and walk up smooth surfaces.

All spiders eat bugs and insects but they are separated into 2 different groups according to the way they catch their prey. Hunters, such as Jumping Spiders and Wolf Spiders, do not spin webs, but actively hunt and seize their prey. Trappers, such as Garden Spiders and Trap Door spiders, made webs and lie in wait for their prey.

Let’s spend some time learning about spider silk. Many arachnid species have been using the same genetic silk recipe for the last 125 million years and for good reason. It has been discovered that spider silk is more flexible than nylon and is five times stronger than steel.

Everyone knows that spider webs are made with silk. But what are the components of that web? Each web begins with a single thread that the spider releases into the wind. This single thread forms the foundation of the web. With any luck, the free end of the thread will catch onto another branch. If the thread catches on to something, the spider cinches the silk up and attaches the thread to the starting point. The spider walks across the thread, releasing a looser thread below the first one. The support structure of the web is formed when this thread is attached to both ends and the spider climbs to its center. This is known as the frame thread. The looser strand sags downward, forming a V-shape. The spider lowers itself from this point, to form a Y-shape. The spider continues to create frame threads between various anchor points. Then it begins to lay out non-sticky radius threads from the center of the web to the frames. After building all the radius threads, the spider lays more nonstick silk to form an auxiliary spiral, extending from the center of the web to the outer edge of the web. The spider then spirals in on the web, laying out sticky thread and using the auxiliary spiral as a reference.

Biology of the Invertebrates, 4th edition. Jan Pechenik.

 Once completed, the spider sits in the middle of the web and patiently waits for an unsuspecting insect to fly into its trap. Once its prey hits the web, the spider will feel the motion through the radius threads and make its way to the vibration source. These spiders have the ability to tell the difference between vibrations from insect prey and other sources (such as a breeze, or a leaf falling into the web). Many species can also distinguish the characteristic vibrations of dangerous insects, such as wasps.

Spider eating bee.

Spider silk is a fairly new area of study for Arachnologists and its use holds much promise for the human world.  In a 2002 issue of the Science journal, the US Army and a Canadian biotechnology company reported that they had manufactured and spun the first man-made fiber with mechanical properties similar to that of natural drag line silk. Creating silk is difficult and time consuming (spiders only contain a small amount of silk and mass rearing spiders is a difficult, if not impossible undertaking) but this discovery opens up many potential applications of silk: Body armor (similar to Kevlar), ropes, athletic attire, and medical device components. The list can go on and on.

All spiders have venom but in most arachnids species the venom is not toxic to humans. These eight-legged creatures prey on small insects and do not have the venom geared towards large animals, such as humans. The mouth parts of a spider are not even capable of piercing human skin. Most spiders do not want to bite, but in the unlikely event that it does happen, it’s usually because a person steps on an arachnid with a bare foot or reaches into an article of clothing that the spider currently inhabits.

A great deal of research has gone into spider bites and several studies have discovered that most “spider bites” are not spider bites, but rather allergies, skin reactions, chemicals, biting fleas or bedbugs, infections, poison ivy or oak, among other possibilities. 

Although spiders may be hated and are low on the cuteness meter, they play an important part in our world. That pesky spider that has set up shop in the corner of your ceiling or the baseboard may be preying upon unseen insects in your home, insects that are more likely to bite humans. Spiders can also be a farmer’s best friend. Arachnologists have estimated up to 11,000 spiders per acre in woodlands to more than 2.5 million individuals in a grassland acre. Since each spider in a field may consume at least one insect per day, their cumulative effect on insect populations is significant.  These hungry spiders prey upon grasshoppers, flies, moths, caterpillars, leafhoppers, some bees and ants, and other spiders. If you still dislike the spiders, think about this; spiders are an important food source for birds and other animals. 

Look for an upcoming entry on some of the spider species found in Missouri.

Glossary:

antennae: a pair of sense organs located near the front of an insect's head. Antennae are usually covered with receptors that can detect odors. Many insects also use their antennae as humidity sensors, to detect sounds and some insects (flies) gauge air speed while they are in flight.

arachnid: A variety of arthropods of the class Arachnida, such as spiders, scorpions, mites, and ticks. Arthropods are characterized by the absence of antennae, four pairs of segmented legs and a body that is divided into two regions, the cephalothorax and the abdomen.

genetic (genetics): The branch of biology dealing with heredity. Heredity is a biological process where a parent passes certain genes, such as eye and hair color, onto their children.

natural history: the study of animals and plants.

offspring: new organism produced by a living thing.

thorax: the middle region of the body of an insect.

venom: a poisonous fluid secreted by certain snakes and scorpions usually transmitted by a bite or sting.