Betty showing her skill

Past Issues of Timbergreen Trails These are stories of the walks our collie has enticed us into taking as published in "The Home News", Spring Green's local paper.   The current story is for November 21, 2006

November 14, 2006

A fall and winter activity that never has lost its fascination for me is sitting quietly under the apple tree feeding the birds. Chickadees are the most daring, and within minutes of my arrival, they are lined up waiting to partake of my handouts. Later, if experience holds true, they will have to share their treats with nuthatches, goldfinches, and titmice, but for now, none of the others trust me. Only the chickadee's natural boldness allows it to sit on my hand so readily, as the chances are that many of the flock are youngsters who were not around last year. Their mortality is high and the average chickadee reportedly lives little more than two years, with winter starvation supposedly being the most common cause of death.

Chickadees are members of the titmouse family--small active birds with short, pointed bills, strong legs, and large bright eyes. They are cavity-nesters and, surprisingly, the female often excavates the hole herself in soft rotting wood. She lines the nest with animal fur, downy plant fibers, spider webs or feathers, and lays up to a dozen tiny speckled white eggs. The number of eggs depends on her age (older females usually lay more eggs), timing (the later in the year, the fewer the eggs), and latitude (northern chickadees usually have more eggs than southern.) If the nest is destroyed, she will try to lay another clutch in a new spot.

The birds are usually seen in pairs or small groups. When nesting is over and the young are on the wing, they will form small flocks of eight to a dozen birds that will roost and forage together until spring. Finding food in the winter is often hard, and hunting in groups increases their chances for success as well as providing more eyes to watch for approaching danger. There are five species of chickadees in North America; the black-capped which makes its home to the north, the chestnut-backed found in the Pacific northwest, the Carolina that is found in the Southeast, Mexican found in the mountains of the Southwest and Mexico, and the mountain chickadee found in the West.

Chickadees subsist on a mixed diet of seeds and insects, and most come readily to bird feeders when natural food becomes scarce. They hide seeds and other food items for later use, placing each item in a different spot, and research has proved that one can remember a great number of hiding places for up to a month or more. It has been found that the portion of the brain that is critical for memory of the chickadee and its close relatives is about three times larger than most other birds. They wait out harsh conditions by roosting in protected areas such as tree cavities and are able to lower their body temperature into controlled hypothermia. They fluff their feathers to create air pockets to trap warm air and can drop their body temperatures an almost unbelievable 10-12 degrees Celsius from the daytime level.

The song of the black-capped is a simple, clear whistle, "fee-bee-ee", but the more familiar "chick-a-dee-dee-dee" is the call that gave this bird its name. Researchers tell us that this call is one of the most complex vocalizations in the animal kingdom, and depending on slight variations in the phrases, it can convey separate, unique messages. This call has been extensively analyzed by sonograms and found to consist of up to four distinct units arranged in different patterns. A recent study at the University of Montana in Missoula showed that the number of "dees" indicates the level of threat. They exposed birds to 15 species of live predators, and then recorded their responses. Playback experiments revealed that other chickadees readily detected information in the calls and that the intensity of mobbing behavior was directly related to the size and threat of the potential predator. In particular, alarm calls triggered by small, dangerous raptors had a shorter interval between "chick" and "dee" and tended to have extra "dees". In one case, a warning call concerning a pygmy owl that is a prime threat to southwestern chickadees contained 23 "dees". The researchers concluded that the study demonstrated an unsuspected level of complexity and sophistication in these calls. Thirteen distinct types of vocalizations have been classified, and it is thought that they may have evolved because the birds tend to live and feed in dense undergrowth where birds cannot see each other and must communicate by sound.

When I see the numbers of black-capped chickadees fluttering around me, I can believe their population is stable and thriving, but I found a disturbing report out of the Rouge River Birding Observatory that is located at the University of Michigan-Dearborn. They state that there has been an almost steady drop in the number of chickadees banded there in both spring and fall seasons since 1992, and point out that the Cornell Lab of Ornithology that tracks bird numbers at feeders across the country each winter also shows a similar 15-year decline. Before we become too concerned, however, it is important to understand that bird populations do fluctuate. According to the Cornell report, last year chickadees in the Midwest were 32% below the previous 14-year average; still, it and the Rouge River site had showed a peak in chickadees in the mid-1990s and again in 2001 in the eastern United States. They do bear watching, however, as few birds are more universally enjoyed.

I stood on the path leading up to the woods, mesmerized by the numbers of crows flying overhead. They would have been hard to miss, as they called to one another constantly, filling the air with their raucous sounds. Just when I would think they were gone, another loose group would appear, all heading in the same direction and on their way to who knows where. In the following days, friends Katie and Barbara called to tell of witnessing flocks of literally thousands of blackbirds, and we have to wonder why such phenomena occur.

The first question seems to be why birds join in flocks (or mammals in herds, or fish in schools) in the first place. While there are many theories, the most commonly held seems to be that it serves as a defense against predators, as the more alert eyes that are searching, the greater the chance that threatening predators will be spotted. When a predator does attack, it often seems to become confused at so much prey, and many a hawk has been observed diving right into the middle of a dense flock of birds only to come out empty-clawed because it could not focus on a single victim.

There are probably many other benefits to flocking, such as utilizing the experience of older individuals to discover rich food sources and safe roosts, or learning migration routes. Flocks can be composed of a single family groups, large cluster of birds of the same species, or sometimes mixtures of many varieties. Some species flock only during migration, while others, such as the various blackbirds and crows, tend to move around in groups much of the year. The size of the flocks usually varies during the year, being smallest during the breeding season, and largest in winter when smaller groups often unite and move around together. Ornithologists have observed that flocking birds are much more relaxed while feeding, as a single foraging bird often spends so much time looking around for danger that it cannot concentrate on eating. It is also true that that if there are many bodies, they can sometimes repel a larger common enemy (such as blackbirds chasing a hawk or owl;). Some flocks in late summer seem to be made up of unmated individuals, and joining a group may serve to bring together potential partners. I would also speculate that many birds whose parental responsibilities have been completed for the season might simply be gathering to enjoy each other's company as well as the freedom to wander on vacation.

Sometimes complex behavior can be generated by the application of simple rules, and Craig Reynolds, a software developer for Sony Computer Entertainment, has developed a computer model of flocking that is fascinating. The basic model consisted of three simple behaviors which describe how an individual bird might move in a group based on the positions and speeds of its nearby flock-mates: each individual tries to avoid crowding by nearby birds; each aims toward the average direction of the others; and each works toward the middle of the group. In addition, each reacts only to flock-mates within a certain small area around itself and ignores all others. Following these stipulations, computer birds in his simulation flock tend to operate very much as do live ones.

Glen Dimock, in Research of January 12, 2003, added an aerodynamic model to Reynold's simulation that may explain the "V" formation of some large migrating birds. He takes the original rules (centering, collision avoidance, and movement), and adds one more ­ any increase of pressure on an individual tells it to fly in that direction. With this alteration, his generated geese formed a "V" from random starting positions, and this might indicate that a real bird feels pressure changes over its body from the presence of other flying birds and will move so as to reduce any drag. Glen has also observed that a live goose begins flapping just a fraction of a second later than the goose in front of it, presumably taking advantage of any upwash produced by it. Another twist on this subject, however, has been given by a French team studying great white pelicans that had been trained to fly behind an aircraft for a film. Sensors on the birds' backs indicated that their heart rates went down when they were flying together and they were able to glide more often. "They fly in formation to save energy," team leader Henri Weimerskirch told BBC News Online. "It's not because they are using the upward airstreams of their neighbor, it is because they are able to glide more often."

Observations on flocking by other investigators show that there may be no consistent leaders in a flock. Using a frame-by-frame analysis of high-speed film, Wayne Potts, in Nature in 1984, found that any individual could initiate a change in flock direction (and thus become a leader), which then spreads through the flock in a wave radiating outward. He proposed that birds farther away from the initial move were able to see the wave approaching and prepare to respond before it actually reached them, calling this the "chorus line hypothesis," in reference to the technique used by Radio City Rockettes who anticipate an approaching high leg kick when it is still well down the line. This allows these flocks to exhibit highly coordinated motion and the group seems to turn and maneuver as a single unit. All of this research has worked to keep me looking to the sky for any flocks of birds that might be flying overhead. In spite of computer simulations and lots of theories, I choose to believe, however, that most of the time, birds flock because they feel safer in a crowd and enjoy the company.

If you have ever seen a witch riding her broomstick across the full moon on a Halloween night, you probably noticed the large black crow perched on her shoulder. The American crow often appears in legend and mythology as an omen of doom, presumably because of its dark plumage, harsh calls, and tendency to eat carrion. In Native American folklore, Crow is often seen as a similar trickster to Coyote, although its tricks tend to be nastier and it is never portrayed as a good guy. The crow is seldom appreciated in these days either, for it is well-known for getting into garbage, feasting on carrion and road kill, destroying crops, killing young birds, and being a noisy and messy nuisance. We had our own run-in with the local crow clan when our neighbor released the young long-eared owl that had graduated from the Sauk City rehabilitator's care. Not a crow was in evidence, but no sooner had the owl escaped its box and flown into a nearby tree than the air was full of scolding crows, and they harassed the newcomer until it disappeared into nearby woods.

Where available, corn is a favorite food; otherwise, the crow consumes a great variety of plant and animal matter--seeds, garbage, insects, mice, and carrion. Most of us know that owls disgorge pellets containing indigestible remnants of their meals but many are not aware that crows, as well as many other species of birds, produce pellets as well. If one looks under a crow roost one can often find hundreds of clumps of grain, hair, and gravel that might be easily overlooked.

Kevin McGowan, a researcher at Cornell University, has been studying crow behavior since 1989. He and his student helpers have banded hundreds of four-week-old nestlings and followed their movements. "Most young birds (of other species) leave their parents soon after leaving the nest... but crows stay with their parents for up to five years or longer." McGowan explained. "Crows almost never breed before they're 2 years old and most don't leave home until age 4 or 5," he said. "While they wait for a breeding opportunity, most help their parents raise additional young and defend the nest."

A new study from Cambridge University, suggests the cognitive abilities of crows are similar to those of chimpanzees, and concludes that, although they have very different brain structures, both crows and primates use a combination of imagination and thinking ahead to solve similar problems. The study states that a crow has an unusually large brain for its size, and that it is "relatively the same size as the chimpanzee brain". The crow is probably Wisconsin's most intelligent wild bird, having its own language with more than 20 sounds and even able to count up to four or five. Some have been taught to mimic words and short phrases (splitting the tongue is supposed to allow it to talk but this is a cruel myth) and one researcher was able to differentiate 23 distinct phrases used by a flock of crows he was studying.

Clarence Stevens, in his book Birding in Metro Halifax, records this story. His father was out looking for a lost cow early one foggy morning when he distinctly heard a voice say his name: "Hello Walter." The second time he heard the voice, he saw the speaker ­ a crow sitting on a nearby fence. He was completely spooked, but later learned that a local man also named Walter had taught the crow to talk. Stevens also recounted a second story that told of a crow that tormented a feeding gull by plucking at its tail feathers until the gull lost patience and attacked back, only to have the crow fly up over its head and swoop down to grab the food.

Another amazing account of crow behavior is found in the Firefly Encyclopedia of Birds, and tells about carrion crows on a university campus in Japan. The birds routinely place walnuts on the pavement at intersections during red lights. When traffic resumes, the walnuts are crushed by vehicle tires passing over them, and the crows return to claim their reward. If the cars miss any nuts, the birds sometimes hop back and try them in another spot. Now California crows have been seen using the same technique, and it is believed that the observant birds had noticed cars driving over nuts fallen from a walnut tree overhanging a road. The birds on the seashore already knew about dropping clams from a height to break them open, but found this did not work for walnuts because of their exceptionally hard shells.

Even more impressive evidence of intelligence comes from New Zealand where researchers found that crows on New Caledonia Island make tapered serrated tools from leaves, and use them to prod and extract grubs and insects from holes and crevices. One captive New Caledonian crow, called Betty, was made famous when scientists at Oxford University filmed her making hooks from straight pieces of wire to obtain out-of-reach food.

The crow appears to be the biggest victim of West Nile virus, a disease recently introduced into North America. Crows die within one week of infection, and few seem able to survive exposure. Female mosquitoes, mainly of the Culex family, bite infected birds, carry the virus in their salivary glands, and infect other birds and occasionally mammals (including humans) when they bite again. There is evidence that shows American crow numbers are declining, most notably in the mid-Atlantic and in the Midwest regions. Despite their poor reputation, it would be a great tragedy to lose these interesting birds.

October 24, 2006

We have always boasted that our neighborhood had some of the most spectacular autumn color to be found in the state, but this year has been a disappointment. Granted that a few red maples did shine out like beacons and some of the oaks have taken on their usual fall gold, rust, and mahogany colors, but the display is nothing to what we have become accustomed to expect. What happened?

Chlorophyll, the compound most responsible for the manufacture of carbohydrates by plants, gives leaves their green color. It breaks down under bright sunlight but as long as plants are actively growing, enough chlorophyll is produced to keep them green. Other pigments are also present that serve as energy absorbers and help chlorophyll do its job. They appear mostly yellow and orange in color but they are not visible as long as chlorophyll is being manufactured in the leaves. The amounts of these other pigments in various plants depend on the particular tree species, soil acidity, and the availability of trace minerals in the soils where the trees grow.

A common misconception about leaf change is that the leaves are dying, but actually the development of fall colors is an active process, and trees must be alive to undergo the change in color and to drop their leaves. When a number of warm, sunny autumn days and cool but not freezing nights come one after the other, it's going to be a good color year. In the daytime, the leaves can produce lots of sugar, but the cool night temperatures prevent the sugar sap from flowing down into the branches and trunk. Researchers tell us that anthocyanin, which give leaves the brilliant shades of red, purple and crimson, is produced as a form of protection. It allows the plant to recover nutrients in the leaves before they fall off, making sure the tree will be ready for the next growing season. The yellow, gold and orange colors created by other pigments called carotenoids remain fairly constant from year to year because they are always present in leaves (although usually masked by chlorophyll), and the amount does not change in response to weather.

Longer nights cause the development of a corky layer of cells between the leaf stalk and its twig, slowing the transport of water and carbohydrates and consequently reducing the amounts of chlorophyll. Food manufactured by the remaining chlorophyll builds up in the sap of the leaf, and anthocyanin is formed which causes the leaves to turn red or purple in color, depending on the acidity of the sap. For example, sumac almost always turns red because red pigments are present and its leaf sap is acidic, while many of the oaks and sometimes ashes will get a purplish color because the sap is less acidic. Trees like birch and aspen do not have much orange pigment, so they appear mostly yellow in the fall. Others do not have as much yellow pigment, and turn mostly orange or red. The brown color of many oaks and hickories can be attributed to a buildup of tannin that is a waste product in the leaves. There are endless variations of pigmentation in trees that changes as the fall season progresses.

Weather throughout the fall season has much to do with the development of fall color in trees. Cool night temperatures destroy chlorophyll quickly, but below freezing temperatures also inhibit production of red pigments. The brightest displays of color occur when we have an early fall of bright sunny days and cool nights, as these are excellent conditions for the development of red pigments. Cloudy days and warm nights will produce less brilliant colors because chlorophyll breaks down slowly and the red pigments are not formed quickly enough. Dry weather causes a greater buildup of sugars in the leaves, enhancing the production of the red pigments. Windy, rainy weather causes many leaves to fall prematurely, lessening the intensity of the display. A killing frost will destroy the leaf cells and the coloration process will not function effectively.

When researchers first discovered that certain tree species manufacture the red pigment in their leaves only during the autumn season, they were disturbed because the process uses valuable sugars that could help the tree survive the winter months. Recently, two independent groups have suggested the interesting theory that the red pigment may act as a sunscreen. When the chlorophyll decreases in the autumn, sunlight can easily destroy the leaf's tissues, explains William Hoch, a plant physiologist at the University of Wisconsin in Madison. Red pigments, he suggests, stop sunlight from destroying its tissue, while allowing just enough photosynthesis to drive the tree's delicate salvage operation. Hoch's research, which appeared in the September issue of the journal Tree Physiology, shows that tree species native to sunny northern climates contain the most red pigments -- evidence, he says, that the pigment is protecting the dying leaves from sunlight. Still, other researchers point out that trees lacking red pigments seem to manage fine without them so it is assumed that there is much more to learn about the process.

The frequently recurring rain and clouds continue to obscure what color is present, but perhaps next year will bring conditions more favorable to pleasant woodland walks. In the meantime, take advantage of any sunny days that do come our way to look around and enjoy what remains.

If you happened to notice a flock of very small busy birds visiting your back yard this week, chances are they were myrtle warblers. Birdwatchers tell us there are two general principles of warbler identification: if there are lots of them, they are probably myrtles and if they are also easy to see, they are almost certainly myrtles. This is true because myrtle warblers are extremely common, and while most other warblers are very shy, myrtles fly about in plain sight. In addition, they are highly social, sometimes moving around in flocks of a hundred or more, and occasionally even sleeping together in large communal roosts. Then too, they migrate through later in the autumn than most other warblers.

"Myrtle" is the name given to the eastern race of the yellow-rumped warbler and the bird can usually be identified by its black-streaked breast, its distinct yellow rump and white tail spots. Unlike many other warblers, it prefers shrubs and small trees instead of high treetops, and consequently is much more often seen than its relatives. Most warblers are insect-eaters but the myrtle can live for long periods of time on berries and fruit. It is particularly fond of the myrtle berries (also known as bayberries) and also relishes seeds from Virginia creeper, red cedar, dogwoods and poison ivy. The bayberry is native in sandy swamps or wet woods and its fruit consists of clusters of round, 1-seeded, somewhat berrylike nuts covered with a whitish wax. Myrtle warblers are thought to be one of the few vertebrates that can digest wax--a major constituent of wax myrtle and bayberries. They nest from the Upper Peninsula northward into Canada, but spend the winter months throughout the southeastern section of the country, from Illinois and Ohio down into Central America.

Warblers are interesting birds and we enjoy having them visit, if only for the short periods during the spring and fall migrations. At least 36 species, each with their own colorful patterns and distinct vocalizations, migrate through Wisconsin from winter homes in Mexico, Central America, South America and the West Indies. A few species stay with us at the farm over the summer such as the yellowthroat with its "Wichity, wichity, wichity" call, the blue-winged warbler, the yellow warbler, and the ovenbird. The blue-winged warbler, an olive-green bird with a yellow head and a thin black line across its eye, spends winters in Mexico down to Panama. We always know when this bird is present by its song, a buzz with the second note lower and slightly trilled. The male yellow warbler is bright yellow as its name suggests, variably streaked with chestnut below throat, and travels into Mexico and sometimes south into Central and South America. Another summer resident, the yellowthroat, with its bright yellow breast and black mask will be wintering as far south as Central America and the West Indies. The ovenbird is sparrow-sized and resembles a small thrush with striped breast and brown back. A few of these may migrate only to the Gulf coast, but most go on into Central and South America.

The redstart, the prothonotary, chestnut-sided and cerulean warblers, and the yellow-breasted chat also nest in the southern Wisconsin but we have seldom encountered one of them. Otherwise, most warblers travel farther to the north and spend the summer months in Canada. Warblers have generally declined in numbers over the years, reportedly due to loss of habitat and the break-up of large forested areas. Roads and development invite raccoons, blue jays, and especially cowbirds that live near the forest's edge into the interior where songbirds nest and can make life precarious for them.

Warblers are small, colorful and extremely active birds with sharp, short beaks. They can be gray, olive, or green, and many are patterned with bright yellow, red, orange, blue or black and white with plain, streaked or striped underparts. With a few exceptions, the warblers that summer in the United States and Canada migrate south because they are so dependent on insects, unavailable during northern winters. Some may make journeys of 2,500 miles including the nonstop 550-mile flight across the Gulf of Mexico. Warblers must feed constantly to fatten up for their long flights south, so they may stay in a food-rich area for days at a time. Most migrate at night and it is said to be possible to hear their soft "chip" notes as they fly overhead if one listens carefully. I've also heard that many bird-watchers go out early in the evening on moonlit nights and watch the silhouettes of passing birds crossing the moon through their binoculars.

These birds play an extremely important role in the ecology of North American forests. Their arrival as the trees leaf out is timed well with the emergence of many destructive insect pests, especially caterpillars. (I have worried about the current widespread practice of spraying the woodlands with Thuricide, a caterpillar-killing fungus applied to deter gypsy moths but that no doubt killing off other caterpillars as well). These birds work over the trees from top to bottom, gleaning the insects that are emerging. Interestingly enough, studies have shown that the part of the tree covered is somewhat species specific. Some species feed at low and mid levels (myrtle warbler), some on the trunk and branches (black-and-white warbler), some feed at mid levels near the outside (black-throated green warbler), some at mid level on the inside (blackburnian warbler), and others feeding at the uppermost portion of the tree (Cape May and cerulean warbler). Are there warblers in your yard or woodland right now?

October 10, 2006

There is little doubt that the soybean fields adjacent to our farmyard produce far more Asian ladybeetles than we consider necessary. This point is brought home each year as the plants mature and dry up, and the ladybugs, finding that their aphid buffet has disappeared as well as the long warm daylight hours that nurtured them, have come looking for a snug place to spend the winter months. Having a soybean field as a neighbor isn't all bad, however, as it also hosts considerable numbers of another much more welcome insect, the clouded sulphur. This small butterfly has become extremely common with the spread of cultivated legumes, but is its size and relatively modest coloring makes it easy to ignore.

The upper surfaces of male clouded sulphur's wings are a bright, clear yellow with solid black edging, but neither it nor its less colorful mate are likely to hold their wings out quietly for inspection. Both are energetic fliers and when they do land, they hold their wings tightly together showing only the less attractive undersides, These are paler in color with one silver cell spot rimmed with orange-pink in the center of the hind wing and some dark spots on the forewing. There is also a variation that is greenish-white rather than yellow, and only the black edges of the wings prove it is not a cabbage butterfly.

Clouded sulphurs often have three broods a season, but we seldom notice them until this time of the year when other larger and showier butterflies have disappeared. The female lays her chartreuse-colored eggs singly on the leaves on a clover or bean plant and in a few days, each egg produces a bright green caterpillar that has a dark stripe down its back and a lighter green stripe on each side. I was surprised to see several males courting an obviously alluring female this week and wondered at their timing, only to read that their larvae will not mature this fall, but over-winter as caterpillars.

In areas where temperatures drop below freezing during the winter, at least one stage of a resident butterfly's life cycle must be resistant to freezing if the species is to survive. Whether this stage is egg, caterpillar, pupa, or adult, all enter into a state of suspended animation during this time known as diapause. This is not brought about by the harsh conditions as one might think, but rather by less obvious stimuli that warn of a change to come, such as shortening days, dropping temperatures and diminishing quality or quantity of food.

Several processes seem to take place in diapause: first, the hormones that cause the insect to develop and grow are blocked in such a way that all maturation stops; then, any ice-forming agents in its cells are removed or inactivated, most of the cellular water migrates to the spaces between the cells, and glycerol, similar to the main ingredient in automobile antifreeze, is even synthesized by some insects to protect any remaining fluid in the cells. The details of the processes involved in these changes are under study, and when it comes to the influence of environmental factors like photoperiod and temperature, there is much to be learned.

The clouded sulphur typically survives our winters by entering diapause after its second molt as a caterpillar, hiding under dried leaves or old logs. Some, however, along with some mourning cloaks and question marks, have been seen to migrate, moving southward in groups of thousands, although exactly where all of these butterflies go is not known. Monarchs are the most heralded of the insect travelers, of course, and we do know that most of those from this section of the country spend the winter in roosts in the mountains of central Mexico. Other adult mourning cloak, comma, question mark, and tortoiseshell butterflies wait out the inclement weather in woodpiles, niches of unheated buildings, and under loose tree bark in the woods.

The red admiral butterfly (don't you love all these odd names that have been given some butterflies?) is also visiting our fading flowers these early autumn days. This handsome insect is mostly black with white spots near the wing tips. The forewing has a bright orange-red band across the middle, and the hindwing has another band along the edge. It is a common butterfly that inhabits North America from central Canada through the Mexican highlands, where typical habitat is rich, moist bottomland woods containing larval host plants such as stinging nettle. Adult red admirals butterflies prefer sap flows on trees, fermenting fruit, and bird droppings and they visit flowers only when their other foods are not available. One of my sources states that red admirals experience diapause, but most report that these butterflies, too, migrate to warmer climes.

Our flower garden that has been alive with butterflies all summer now stands virtually abandoned and forlorn. We miss the beautiful insects that have frequented it, but we know that next year they will be back in all their glory.

October 3, 2006

Despite the dismal weather forecast that promised rain with possible thunderstorms followed by a sharp drop in temperature and perhaps our first major frost, yesterday was party sunny and, although breezy, not at all unpleasant. Obviously the birds were well tuned in to the omens, however, for they were all a-twitter and bustling around the farmyard in spectacular numbers. Most vocal were the bluebirds, and dozens of them visited the pond and environs, the adult males resplendent in their bright blue coats with reddish vests, and the adult females and young only slightly less colorful. Both male and female bluebirds sing, although now all we hear is "chur-lee", an all-purpose call the birds use to talk to each other.

Our bluebirds were historically birds of the savanna, areas of grassland with occasional trees scattered throughout. A more accurate description might be oak woodland and brush land intermixed with open prairie. However, as European settlers cleared the eastern forests for homesteads and pasture, they created large, open areas that provided exactly the kind of habitat that the birds needed, and they quickly moved into it. Forest clearing reached its peak around 1830, and as an additional bonus to the birds, wooden fence posts were erected around fields that provided additional nesting holes as they rotted.

A major problem arose about the same time, however, as English sparrows and European starlings were released into the wild, both very aggressive cavity nesters that competed with the bluebirds for nest sites. (We soon learned to locate any birdhouses away from our farmyard, as the resident sparrows immediately took possession, driving any bluebirds away.) Then, too, it gradually became common farming practice to clear out fencerows, install steel fence posts, and cut any dead or dying trees, thus depriving the birds of nesting sites. Their numbers declined drastically until bird lovers intervened and began providing and monitoring nest boxes throughout the eastern section of the country, allowing the population to rebound.

In late August and September, bluebirds molt, and it is at this time that the young of the year loose their spotted breasts so that they resemble adults. Some of them winter in the southeastern states and even down into Central America, but if food is plentiful they sometimes stay in the vicinity of their nesting area. During the summer, bluebirds feed mostly on insects, either hunting in the grass or snatching them from the air, but during the fall and winter, fruits and berries make up a major part of their diet. Small flocks of wintering bluebirds are not an uncommon sight in southern Wisconsin where they feed on native berry-producing shrubs such as red cedar, grapes, and dogwood. Should you want to put out food for them during the winter, you might combine equal volumes of peanut butter, quick cooking oatmeal, and yellow cornmeal with melted suet.

There are five other species of thrushes commonly found in Wisconsin, including our American robin. Like the bluebirds, many robins depart for milder climates in early fall, traveling as far as Guatemala and beyond, but others remain in the northern states if sufficient food is available to them. They are considered short distance migrants and can usually be found in large, somewhat nomadic flocks, their numbers varying each year with the local conditions.

The other thrushes, often clumped as the brown-backed thrushes, include the wood, hermit, Swainson's and veery. They are woodland dwellers and so much less visible, although they produce some of the most beautiful sounds of summer. These species usually begin to gather, first in family groups, then in larger flocks in late August, and most have disappeared from their breeding grounds by October. The hermit thrush is the only one of the brown-backed thrushes that winters in North America and then only where the average January temperature is above 30 degrees Fahrenheit and where there is a supply of open water. The veery, Swainson's and wood thrush all migrate to spend the winter in Central or South America.

Thrushes are generally compact, small to medium-sized songbirds with an upright posture. They often hop along the ground, snatching up insect and worm prey with their straight, relatively thin bills. Juveniles of almost all species have prominently spotted underparts while some adults have brown plumage with various amounts of spotting and others are brightly colored with none. Blue jays, grackles, crows, raccoons, weasels, squirrels, chipmunks and snakes eat thrush eggs and nestlings as most species build open cup-shaped nests secured to branches of low trees and shrubs or on the ground. Exceptions are the robins that often nest on building ledges, and bluebirds, the only cavity-nesters.

The thrush family is highly regarded wherever its members are found, and we feel privileged to have so many call our farm their home, at least for a part of the year. We have to assume many have already left for safer climes, and soon, most of the rest will disappear, as well, but we will be watching throughout the winter for a flash of blue against the snow, and eagerly await their return come spring.

September 26, 2006

The recurring rains have kept the soil moist and soft and the underground dwellers are taking good advantage. There are long ridges across the surface of our lawn marking tunnels of our resident moles, and there are numerous entrance holes around the area indicating that various other animals are active, as well. Most of the larger mammals such as coyotes, woodchucks, badgers, skunks, raccoons, opossums, weasels, and rabbits use underground burrows only for housing their young, but many of the smaller animals spend much of their time beneath the surface.

Mice and voles are our most common and prolific rodents, but there are also plenty of other interesting species. The eastern chipmunk digs its burrow with sharp-clawed front paws, kicking dirt out with its hind feet or pushing it with its head. The dirt is shoved to the surface and then carried away in the animal's cheeks so that there are no dirt piles around the hole. The tunnel system can be as long as thirty feet and two to three feet below ground, with one main entrance and secondary exits nearby. Except for mothers with litters, chipmunks live alone and will vigorously defend the area around their burrows.

The chipmunk spends a large part of its waking hours gathering and storing food for the winter. It is very vocal and has a vocabulary of about thirty distinguishable combinations, from a loud, shrill "chit-chit-chit" to softer, slower chucking sounds, and also uses tail waving and other body language. Its "chit-chit" call caused the Algonquin Indians to call it a "chit-monk", a name picked up by the English settlers who heard it as "chipmunk". The eastern species is about 10 inches in length including a 4-inch tail and weighs around four ounces. It has reddish-brown fur on its back and sides and white fur on its stomach with two white stripes bordered by black on its sides and one black stripe down the center of its back. Most of the chipmunks in Wisconsin are of this species, although a similar-looking but smaller western chipmunk sometimes can be found here, as well.

A chipmunk will eat a wide variety of food -- mostly acorns, nuts, seeds, berries and fruit, as well as slugs, snails, aphids and other insects, and has also been known to eat birds, eggs, mice, and even small snakes. The chipmunk's mouth is small, but its cheeks can expand to three times its head size and it uses these to carry large amounts of food back to its den. Although chipmunks bury some nuts and seeds in the ground, they store most of their food in their burrow for winter. The eastern chipmunk doesn't truly hibernate, but does spend a lot of time sleeping and may go into a state of torpor although it wakes up every few weeks to eat the food it has stored.

The thirteen-lined ground squirrel is about the same length as the chipmunk but is more slender. As its name suggests, 13 stripes run the length of its body, with five of the light-colored lines breaking up into a series of spots as they progress down the back. Its original range was limited to the prairies of the Great Plains but when Europeans arrived and established pastures and fields where forests had once stood, the thirteen-lined ground squirrel was quick to move east into these new areas. At least 50% of its diet is animal matter -- grasshoppers, caterpillars, beetles, cutworms, ants, insect eggs, mice, earthworms, small birds, and even another ground squirrel -- while the rest is seeds, roots, vegetables, fruits, and grains.

This animal spends the winters in true hibernation: its body temperature falls to about 40 degrees Fahrenheit, its breathing almost stops, and its heart beat drops to about 5 per minute -- as compared with the summer normal rate of 200 to 350. It uses up all of its stored fat resources as it sleeps, and must store sufficient food for when it rouses, until it can forage outdoors again.

The Franklin ground squirrel is another Wisconsin rodent that has almost the same habits as its 13-striped cousin but is considerably bigger. It is unmarked gray or brownish and its tail is rather bushy, so that it can be mistaken for the tree-dwelling gray squirrel. Its burrow openings are larger and the dirt is piled at the mouth.

Also present is the pocket gopher, so called because it has a large fur-lined pouch on the outside of each cheek, in which it carries food. It is about the size and color of a rat and has strong forelegs and heavy claws for digging and a short, hairless tail. It is active all year long, but seldom shows itself above ground. The pocket gopher feeds on roots and bulbs that it finds by tunneling through the soil, and upon green food about the holes. It has four large, chisel-like front teeth, two on the top and two on the bottom, that are actually located outside the mouth so that the gopher can close its lips behind its teeth while digging to keep from swallowing unwanted dirt. These teeth can grow up to 14 inches in a year and must be continually worn down by chewing or they would grow right up through the top of the animal's mouth.

I have never been able to determine what animal or animals inhabit my garden, as they are careful never be seen, but I certainly am aware of their presence. Seeded corn and beans disappear without a trace, melons are repeatedly plugged until they ripen to their taste, and berries disappear from their bushes although covered with netting to protect them from marauding birds. Still, there is plenty left for us humans, and that is part of gardening in this lovely spot in which we live.

September 19, 2006

The woodlands and edges are entering their most colorful period, with the walnuts and sumac leading the way. Few flowers in the forest bloom now with one notable exception, the white snakeroot, that seems to be able to flourish despite fierce competition for water and sunlight. This is an erect, branched plant usually about 3 feet tall with small clusters of white blossoms.

White snakeroot is described as a native perennial, but in our woods it seems to act more like an annual for we see no sign of any until the young plants reach blooming size in September. Then, the numerous heads of tiny white flowers at the top of each stem and the ends of the branches are visible throughout the wild garden, looking almost exactly like the flower heads of the familiar garden ageratum, except for color. Although the plant is a member of the daisy family, its blossoms consist only of tubular disc flowers such as are in the centers of asters and sunflowers, and possess no rays (petals) at all.

An interesting fact about this plant is that it is very poisonous, both to grazing animals and to humans who might drink milk from cows that have eaten it. Nineteenth century pioneers sometimes abandoned their land after observing the spread of "milk sickness" which caused a number of deaths, assuming the disease was present in the soil. The sickness reached epidemic proportions before the true cause was discovered, and it is thought that this was the cause of the death of Nancy Hanks, mother of Abraham Lincoln. All parts of the leaves and stems are toxic and remain so even when dried in hay.

Many of our plants, both wild and in our gardens, contain chemicals that are toxic. Most only become harmful as part of the digestive process, but some affect humans and animals when simply touched or even breathed in. Their harmful chemicals are products of the very proteins and amino acids that are necessary to all living cells, most of which are highly beneficial. Deadly poisons such as those in the amanita mushroom or in the algae known as red tide are created if more than two chains of amino acids are joined in a particular fashion. Some alkaloids are nitrogen-bearing chemicals that are derived from amino acids and are useful medicines, but others are bitter-tasting and destructive such as baneberry, nightshade, and some spring flowers. Other compounds which can become toxic are glycosides such as those found in foxgloves and some roses, oxalates that are present in philodendrons and even rhubarb, phenols, such as those found in poison ivy and nettles, and resins and volatile oils, derived mostly from chemicals composed of hydrogen, carbon & oxygen, and present in many unrelated plants.

It takes little imagination to understand the benefit to plants offered by poisons in their leaves, for they are the foodstuffs at least indirectly for every living creature on earth, and those who possess such toxicity often survive to produce offspring while their nearby neighbors are consumed. Certainly, for a late blooming plant like the white snakeroot that stands tall and inviting among plants that have completed their growth and are fading, it would be very important to be as unappetizing as possible.

Another poisonous plant is also just opening on the prairie, most often where the soil is moist and water is plentiful. The common sneezeweed can reach 60 inches in height, and is usually identifiable by its oval or heart-shaped toothed leaves arranged opposite to each other up its winged stems, but it is the numerous flowers that make it stand out. I've always had a fondness for this particular plant as its scientific name is "helenium" or Helen's flower. In its long-ago past, tradition links the plant with Helen of Troy, and depending upon the source, either Helen carried the flower when Paris took her to Troy or else it sprang from her tears. Even a disease found in sheep that have eaten the plant is named for the flower--helenatin. Sneezeweed has many bright yellow flowers that consist of prominent buttons surrounded by turned-back rays, each with two or three notches in its lower edge. This plant is very bitter, but like many other of the toxic plants was used in small quantities to treat many ailments in years past. Its common name was derived from the practice of treating respiratory illnesses with a snuff of dried and powdered plants as it induced sneezing.

All of this talk of plant toxins should underline the general rule that no part of an unknown plant should be tasted, or even picked without using caution. It is a modern myth that all things "natural" are more healthful to use. Some of the most deadly poisons known come from natural sources, and most of these are plants.

September 12, 2006

My last caterpillar has spun its cocoon, after weeks of chomping down the fresh leaves that I had to provide for it and its fellow larvae every day, come rain or shine. They were the offspring of the female promethea moth whose cocoon had spent the winter in the shed. After she hatched and mated with a local Lothario two months ago, I retained several dozen eggs before releasing both moths, and have been tending them ever since. Half of the hatchlings were placed on a shrubby black cherry clump on the ridge under netting, while the others grew up in my insect cage.

All butterflies and moths have an almost unbelievable lifestyle when you think about it, going through a four-stage process that includes an egg, a larva which looks much like a fat worm with multiple pairs of legs that aren't even real legs and eats leaves, a pupal stage that seems as though nothing is happening on the outside but in which the insect is completely remaking itself inside, and finally, a sexually mature adult insect with large showy wings that sips up nectar if it eats at all. Scientists contend that this process is one of the key elements that explains why insects are so successful, as immature insects are able to take advantage of a wide variety of readily available foods while the adults can easily fly to new areas. Still, how could this complicated system have evolved?

The strangeness of the process is made more so by the fact that some ninety-five percent of all animal species are insects. Now consider that nine out of ten of all the insect species go through virtually this same process as do our butterflies and moths. In other words, most of the creatures on earth have this complicated growth sequence, and scientists seem to have made limited progress in understanding it or how it could have come into the evolutionary process.

Researchers tell us that the twelve percent of insect species that do not experience the complete metamorphosis briefly described above were the earliest to appear on earth, perhaps 300 million years ago. These have three stages rather than four: the egg, a nymph that looks and acts like much like its adult phase but without wings, and the adult. Our commonest instances of this segment of the insect population are the grasshoppers, crickets, and cockroaches. The immatures that hatch from their eggs are recognizable immediately despite their size, their lack of wings, and their larger heads in relation to their bodies. They then pass through a number of growth stages, in which they gradually take on adult characteristics. Each is marked by a molt, during which the old skin splits and is discarded, revealing a new larger one, until the final shedding which exposes the adult, most often with wings.

We are told that an immature insect's growth and metamorphosis are controlled by hormones produced by endocrine glands near its head. Some cause gradual alterations in its body in conjunction with a series of molts, while others seem to act to prevent the development of adult characteristics. The actions of these hormones, and thus the physical changes, are controlled by the particular insect's genetic makeup, and how long it remains in any of the various stages depends upon its species. A housefly spends one day as an egg, two weeks as a grub, one week as a pupa and lives on for two weeks as an adult. A monarch butterfly exists four days as an egg, two weeks as a caterpillar, ten days as a chrysalis, and two to six weeks as an adult. A cicada spends one month as an egg, up to seventeen years as a nymph, and two months as an adult with no pupal stage. A mayfly lives one month as an egg, three years as a nymph, and no more than a few hours as an adult.

A new study at the University of Washington concerns a particular gene that has been known to be present in a moth caterpillar only at the point when it changes into a pupa. Now the same gene has been identified in the developing nymph of a cockroach throughout its early stages, only disappearing before the final molt. The researchers suggest that this might be evidence that the nymphal stage in the more primitive insects is equivalent to the pupal stage of advanced insects such as butterflies, and that somehow this gene is responsible and necessary for the radical change from larva to pupa. They also conjecture that it might have been this gene that mutated in the distant past to begin the process that led to the more complicated metamorphosis.

All of this is most confusing and certainly does not give us the understanding of the process we would like to acquire, but it does indicate that studies are ongoing and that progress is being made. In the meantime, think of the mystery involved in its growth any time you see a butterfly flutter by, a beetle make a meal on your roses, or a fly buzz on the screen.

September 5, 2006

When our grandchildren were young, one activity that we all enjoyed at this time of the year was to have a rainbow mushroom hunt, seeking out the elusive objects by color and often finding a surprising variety. We have never become anything close to being adept at fungus identification, taking as our excuse that there are over 70,000 species, with more being discovered every day. In addition to their vast numbers, most fungi produce their mushrooms (which are the spore-producing organs) for a very short time, and are often separated into different species based largely on microscopic differences.

Unlike plants and animals, fungus bodies are entirely composed of filaments, their cells long and thread-like and connected end-to-end. They may be very small or they may cover many acres, but all contain chitin, the same substance that occurs in the exoskeletons of insects and spiders. They usually live hidden in the soil, wood, or another food source until they eventually develop mushrooms, puffballs, truffles, shelves, cups, "birds nests," "corals" or other fruiting bodies.

Fungi feed by secreting acids and enzymes into the host material that break its tissues down into simple molecules they can absorb. Most fungi feed on dead or decaying material, while others are parasitic, feeding on living organisms without killing them. Many of the latter exist in a reciprocal relationship with a plant; in fact, a great many plants rely heavily upon a fungus to aid them in acquiring their food. The fungus, with its large surface area, is able to soak up water and nutrients from a large area and make them available to the plant; in return, the plant manufactures energy-rich sugars through photosynthesis that it provides for the fungus.

As we searched for the mushrooms, it was always exciting to come upon a colony of Indian pipe, often in one of the darkest parts of the woods. Upon first sight, it seemed as though this too must be a fungus because of its waxy white appearance without a touch of green. Nevertheless, it is really a flowering plant and has an interesting life style.

Indian Pipe grows only about six inches tall, each stem with tiny, scale-like leaves and terminating in a single drooping flower. Despite its appearance, small bumblebees visit these flowers for nectar, inadvertently pollinating them. At this point, the flower straightens up, turns black and develops tiny seeds before drying up. Indian Pipe has no chlorophyll and cannot manufacture its own food as do most other plants, and its roots must connect with the filaments of a certain type of fungus to provide it with nutrients. This strange plant can grow in very dark environments because it is not dependent on light for photosynthesis.

There are at least 3000 species of plants that cannot photosynthesize, and many (including the Indian pipe) are members of the family that also includes blueberries, cranberries, rhododendron, and azaleas. These plants must get their food from an outside source and almost all are parasitic on other organisms, usually fungi. These fungi must already have ongoing relationships with suitable trees, and thus the energy ultimately comes from photosynthesis of the tree, passing through the fungus on the way to the Indian pipe.

Thomas J. Volk from the University of Wisconsin-La Crosse reports that this flow of carbohydrates can be easily traced by exposing the tree leaves to a detectable gas. This is accomplished by enclosing the leaves in plastic bags containing radioactive carbon dioxide. The sucrose that the leaves photosynthesize then becomes radioactive and is transported to the roots of the tree where it is absorbed by the fungus. The fungus transforms the sucrose into radioactive sugar alcohols, which are then distributed throughout the fungus and ultimately to the Indian pipe, as well. In return the fungus aids the tree in absorption of water and essential minerals, especially phosphorous, while the flower seems to benefit without giving much if anything back. The Indian pipe absorbs the sugars from the fungus and so the radio-labeled carbohydrates can be traced from the tree to flower.

I came upon an extensive colony of Indian pipe this past week, in contrast to the individual specimens we more commonly encounter, and assume that, just as has been true with many of our other plants and animals, they have responded to the conditions this year with unusual vigor. At a time when the woodland plants are mostly shutting down and disappearing, they are a welcome sight.