Signs of Spring 13: Gypsy Moths and Tent Caterpillars

Photo by O. Leillinger Wikimedia Commons

Photo by O. Leillinger Wikimedia Commons

I was riding my bike down on the Roaring Run Trail last week looking for arriving, migrating birds when I noticed something else entirely. Crawling across the gravel surface of the trail along with a surprisingly small number of forest millipedes (“surprising” because I have notes from last year at this time that the trail was absolutely covered with these millipedes!) were an equally small number, but regularly occurring, crossing parade of gypsy moth caterpillars.

Gypsy moths (Lymantra despair) were/are one of the great invasive scourges of our eastern forests. A brief review of their history: they were brought to North America (Medford, Massachusetts to be precise) in 1869 by Etienne Leopold Trouvelot who intended to breed them with Asian silk moths so that he could develop a domestic silk industry. The gypsy moths escaped from Trouvelot’s home and quickly became a recognized pest in the oak forests of New England. In 1906 the U.S Department of Agriculture released an exotic, European parasitic, tachinid fly (Compsilura concinuata) to try to get the exploding gypsy moth populations under control. Over the next eighty years the USDA repeatedly released more and more of these tachinid flies throughout affected forests in a vain attempt to control the spreading gypsy moths. As pesticides were invented, they were thrown at gypsy moths, too. Pathogenic fungi were also developed and used to weaken and reduce the gypsy moth masses.

Photo by K. Wixted, Flickr

Photo by K. Wixted, Flickr

Those of us of who remember the gypsy moth outbreaks here in Western Pennsylvania in the early 1990’s can recall trees covered with writhing masses of caterpillars, and sidewalks, streets, and driveways coated with their slippery, crushed bodies. We also remember that we had to wear hats when walking in the woods because of the constant raining down of tiny fecal pellets from the swarms of gypsy moth caterpillars feeding on leaves up in the tree canopies. Many oak trees were completely defoliated, and some oak trees were killed. But, then the explosive numbers died back and for most us “went away.”

There are still significant areas of Pennsylvania where gypsy moths are an overwhelming pestilence, but many more areas of forest where they have become a baseline part of a tolerable equilibrium. Maybe the pathogenic fungus was the key weapon for control. Maybe letting the population become so dense and unstable triggered a crash from which the species has not yet recovered. Either way, biking along Roaring Run Trail and dodging a few crossing gypsy moth caterpillars is so much better than the slipping and sliding over thousands of their crushed carcasses just 25 years ago!

Unfortunately, though, those tachinid flies that were released during eighty years of fruitless attempts at biocontrol became established in North America and are doing a great deal of harm.

Let’s think about these parasitic flies and how they interact with their host caterpillars. First, many parasites of moth caterpillars lay their eggs on the surface of the skin of the larvae. Since larvae go through a number of growth and skin shedding stages (their “instars”) many of these surface eggs are in fact shed with each instar molt. Also, many of the moth parasites are very specifically matched to a species of moth caterpillars. Consequently, the parasite becomes active only during the seasonal activity time of the host caterpillar and has a very focused and direct impact on a specific moth species. These two features of the host/parasite interactions enable both species to reach equilibria populations in which persistence of both species without explosive growth is achieved.

Compsiulra concinnata, our introduced tachinid fly, however, exhibits none of these focusing or restraining parasitic features. This tachinid fly inserts its eggs into the body of a host caterpillar. No skin molting will shed the lethal parasite eggs once they have been injected into the caterpillar. Also, this tachinid fly displays the antithesis of host specificity. It parasitizes nearly two hundred species of Lepidoptera (moths and butterflies), Coleoptera (beetles) and Symphyta (sawflies) in North America alone. Further, C. concinnata instead of having its life cycle timed to the seasonal cycle of a particular host has the ability to have up to four generations in a single year. Each generation will encounter different butterfly, moth, beetle or sawfly species and have deleterious impacts on each of them.

There was, then, no targeting of C. concinnata on gypsy moths! Almost every native moth and butterfly species in North America was exposed to this aggressive, generalist parasite! Monarch caterpillars are killed by C. cincinnata, as are luna moths, cecropia moths, polyphemus moths and promethea moths. The decline of these “giant silk moths” in particular has been observed throughout their North American ranges, and some experts feel that C. cincinnata is responsible for over 80% of their population loss!

Photo by D. Gavey Flickr

Photo by D. Gavey Flickr

Looking up from the gypsy moth caterpillars on the bike trail path I notice that the masses of tent caterpillars (Malacosoma americanum) are growing especially thickly on the terminal branches of the cherry trees all along the trail. These caterpillars are an inevitable sign of late spring or early summer, and, while they are not as beautiful as some of the other aspects of the season we have mentioned in the past, they are the principal food of one of the glorious birds in our area: The Baltimore Oriole. As I wrote in a blog several years ago:

Photo by Mike's Birds Wikimedia Commons

Photo by Mike’s Birds Wikimedia Commons

“The oriole males are vying with each other for prime breeding territories and are getting ready for the anticipated arrival of the females. Baltimore orioles (and this species is distinct from Bullock’s oriole so recent attempts to lump both species together as the “northern oriole” are not valid) spend their winters in southern Mexico and Central America and then in the spring spread themselves out across their breeding territories in the United States from North Dakota to Maine and Oklahoma to the Carolinas.”

The orioles time their mating and egg laying and nestling emergence to the abundance of the eastern tent caterpillars! Fast food for fast growing nestlings! As John Irving once wrote in his novel “The Cider House Rules,” “be of use!” He could have been describing the tent caterpillars!

So, caterpillars are all around us! Some are vestiges of a colossal, human generated disaster and others are enmeshed into the natural trophic network and serve as the primary fuel for some glorious baby birds. Sunlight to leaves to caterpillar to majestic orioles: it sounds so simple!

Enjoy the Spring and Summer!

Posted in Bill's Notes | 1 Comment

Signs of Spring 12: Spiders and Stink Bugs

Photo by D. Sillman

Photo by D. Sillman

A couple of days ago I was down in my basement washing up my beer making equipment in preparation to brew a batch of a double IPA for the coming summer. The hardest part of beer making is getting everything clean and sanitized so that there are not too many extraneous, competing microorganisms battling with the introduced yeasts to take the sugars of the brewing wort into odd, biochemical directions. You want as simple of a microbial community as possible in your fermenting system in order to guarantee a predictable (and delicious!) outcome. Brewing, then, is just another branch of applied ecology!

Anyway, making beer mostly involves washing and cleaning equipment, and I was leaning over the big laundry tub sink in the basement, scrubbing my ale pail with hot, soapy water when a delicate cellar spider (Pholcus phalangiodes) (photo above) drifted down on a silk strand from the ceiling over the sink. I did not want the spider to fall into the hot water so I pinched my thumb and pointer finger on the silk line and tried to gently move it over to the safety of the wall shelf. The spider, though, reacted violently to my touching its drop line and immediately released its thread and pitched itself into the hot water below.

I have a long, mutualistic relationship with our basement spiders, and this sudden death (almost an arachno-suicide) upset me. These spiders are active and abundant all year round in our basement and besides eating each other also, I am sure, consume a wide variety of insects that might otherwise thrive in the cool dampness of the basement. I have even seen brown, marmorated stink bugs caught up in the webs of these small spiders (although I have only seen larger, more robust spiders actually feeding on the stink bugs (see discussion and pictures below!)).

So I looked up at the ceiling from which the pholcid spider had come and saw the reason why it was so eager to get away. Wedged next to the floor joist was a large, fishing spider (Dolomedes tenebrosus.) who had been undoubtedly hunting the frail little pholcid.

Photo by D. Sillman

Photo by D. Sillman

Fishing spiders are impressive! Females have a body that can be slightly more than one inch long (about the length of a chap-stick tube!) and legs that can be 2 to 3 inches long! Holding one of these spiders in my hand (which is hard to do because they are very shy and hard to catch!) their legs easily span the width of my palm. We have had fishing spiders in our basement and garage for many years, but I hadn’t thought of their “super-predator” role in our basement ecosystem before. The pholcid spiders, who are active predators themselves, may be the primary prey of these larger arachnids.

The fishing spider stayed in its spot up on the ceiling until I finished scrubbing the ale pale. It was waiting for another snack to wander by and showed amazing patience and focus.

I have written about brown marmorated stink bugs four or five times over the past five years. Their sudden appearance in Western Pennsylvania in the fall of 2010 and their explosive numbers in the springs and falls ever since have made them a very unwelcome sign of both spring and fall.

The brown, marmorated stink bug (scientific name: Halyomorpha halys) is a native of northeast Asia (Japan, Korea, and China) and, apparently, is just as annoying there as it is here! Its use of human habitations as hibernation refuges, and its ability to communicate via pheromones and then aggregate in great numbers in some selected house, barn, porch, garage, or any other stink-bug-determined-suitable building makes their presence both in their native and also in their invasive regions impossible to ignore.

It is thought that this insect was first released into the United States in Allentown, PA in 1996. It apparently traveled from northeast Asia in a shipping container that was delivered either to the port of Philadelphia or Elizabeth, New Jersey and then trucked to Allentown. Five years later this new, alien, invasive species was recognized and identified by entomologists at Cornell University, but by then significant populations were being observed throughout eastern Pennsylvania, New Jersey and New York. This insect has spread to thirty-five states primarily in the eastern United States. It has very large populations in Pennsylvania, Maryland, Virginia, New York, New Jersey, Massachusetts, Delaware, Ohio, and North and South Carolina. It has also spread to California and Oregon allegedly via a car driven by a person traveling from Pennsylvania to California in 2005.

There is a consortium of university and government researchers who are looking into the basic ecology and biology of the brown marmorated stink bug. Their goal is to come up with effective control measures to stem this growing biological invasion. The group (called “Stop BMSB”) is funded by the US Dept. of Agriculture and includes fifty researchers from tem universities (including Penn State!). They even conducted a “citizen’s science” survey last fall to try to determine some of the ecological and behavioral features of this bug. Their “2014 Great Stink Bug Count” asked homeowners to go out around their houses every day to determine the numbers and locations of any stink bugs that are present. Every little bit of data might help!

But here is the interesting thing: when the stink bugs first made their appearance here in Western Pennsylvania almost every potential predator was actively repelled by their pungent scent. Spiders, birds and almost every other type of possible insect eating invertebrate and vertebrate species actively avoided contact with the stink bugs, and, subsequently, their populations grew out of control. In the fall of 2013 and in the spring of 2014 we caught thousands of stink bugs in and around our house. We filled up cases of one liter, plastic bottles with their carcasses! Last fall, though, the huge numbers did not come, and this spring I have caught maybe a dozen total stink bugs over the past month. A far cry from the thousands of just twelve months ago!

Photo by D. Sillman

Photo by D. Sillman

What has happened? Spiders are now actively eating stink bugs. The picture Deborah took of this jumping spider (Phidippus spp.) chewing its way into the captured sink bug is a great example! Birds (especially titmice and chickadees) flare up to the window screens of the house and snag unwary stink bugs. They fly them over to nearby branches and gobble them down! The predator guild of our surrounding vertebrate and invertebrate community has adapted itself to this new (and formerly incredibly abundant) food source! Control has been achieved, at least in the area immediately around my house!

Anyway, my basement spiders are trapping stink bugs even while they are being hunted by the larger, fishing spiders. The birds and outdoor spiders are also establishing a new equilibrium with, apparently, controlled stink bug menace. Invasive species are not always this quickly contained. If anyone is having any stink bug experiences this spring, please let me know!

Next week, another great topic! Gypsy moths! The fun keeps rolling along!

Posted in Bill's Notes | 2 Comments

Signs of Spring 11: Wildflowers on the Nature Trail

Deborah went out on a Nature Trail walk this week while I was giving (and grading) some finals. She spotted (our) first Baltimore orioles of the spring (two males fighting for mating territory along the Spicebush Trail up along the stream). She also saw a number of wildflowers along the trail and has classified them as “plants everyone should notice” and “plants that only biologists are likely to notice.” I have added some discussion about some of the plants. It’s worth taking the short walk out to the trail to see them! The plant names with *, by the way, link to species pages on our Virtual Nature Trail if you would like to read more about them!

Plants that everyone should notice:

Yellow violet flower and leaves

Image credit: D. Sillman

Violets!  Mainly purple and yellow violets – These are the most obvious flowers along the Nature Trail right now. There are many species of violets out in our woods and they range in color from a deep blue-violet to pure white. Left alone violets spread through their shady, moist soil habitats via rhizomes and seeds and can even cross the line from wildflower to weed if they invade flower beds, lawns, or agricultural fields. Their heart shaped flowers are waxy and resistant to many herbicides which make their control as weeds quite difficult. The leaves of violets are used as food by a number of moth and butterfly species. There is an ongoing discussion about the scent of violet flowers. Some maintain that the flowers have no smell while others describe a sweet, powdery scent that seems to come and go. The chemistry behind these observations centers on a ketone called “ionone” that is a major component of the violet flower’s chemical signature. Ionone actually smells initially sweet but then desensitizes your olfactory receptors thus blocking your sense of smell. It takes a couple of seconds for the receptor to recover and then the scent of the violet flower seems to return! Try it!

*Garlic mustard – unfortunately abundant and in full bloom out on the trail! This European, alien invasive species was introduced to North America in 1860. Its use as flavoring herb for food led people to grow it in herbal gardens, but it rapidly escaped cultivation and has spread throughout forest and field habitats in the Northeastern and Midwestern United States and Canada. A single plant can produce up to 8000 seeds, so its potential growth rate spread is enormous. Garlic mustard also produces a rich array of allelopathic chemicals which inhibit the growth of other plants and can even kill the mycorrhizal fungi on which these plants depend for their nutrient acquisition. A final feature of this plant that accelerates its invasion of our ecosystems is that white-tailed deer tend not to eat it! So while almost every other plant in our woods is passing though the digestive tract of deer, the garlic mustard continues to grow, flower and produce its prodigious number of seed!

Mayapple plant with flower bud circled

Image credit: D. Sillman

Mayapple – its distinctive “umbrella” leaves are abundant throughout our woods!.  Flower buds have formed under the leaves (circled on image) and we predict beautiful flowers in about a week. This distinctive “parasol” plant has thick, shiny green leaves and will form a partially hidden, nodding white flower. This perennial plant grows from expanding rhizomes and often forms large, interconnected patches of dozens to hundreds of genetically identical plants. Mayapple relies on soil fungi (mycorrhizae) to assist their uptake of soil nutrients. Competition with plants that inhibit these soil fungi (like garlic mustard) can be very harmful to mayapple. Reproduction in mayapple is via both vegetative growth (the expanding rhizomes) and via sexual reproduction (flowers that form fruit after pollination). There is a steep physiological cost involved in making flowers and fruit, and this cost can significantly drain the energy reserves from the colonial rhizome. This energy loss may even be sufficient to kill the large, clonal colony. Dispersal, though, of the species via the fruit, and the genetic mixing and variation that arises from sexual reproduction are advantages well paid for by this stress.

Spring beauty flower

Image credit: D. Sillman

Spring beauty – almost done!  Delicate white flowers, but you’ll need to look carefully! Spring beauty (Claytonia virginica), in addition to being a very reliable “sign of spring,” is also edible from its root and thumb-sized, underground corm to its green, leafy stem! A number of references describing both food uses by Native Americans and European explorers and settlers include spring beauty (especially its carbohydrate rich corm) as an important food item. It would seem a shame to pull up and destroy such a delicate flowering plant for such a tiny meal, but if you were really hungry I suppose beauty must yield to calories.

And briefly:

Three flowers

Image credit: D. Sillman

Wild geranium – beautiful purple flowers!
*Red Trillium – gorgeous, but you might miss it if you don’t know where it is!
*Jack-in-the-Pulpit – a wonderful wildflower that is fairly abundant on the trail, but it’s green color makes it really easy to walk right by it and not see the flowering parts!
*False Solomon’s Seal – not blooming quite yet, but very distinctive and beautiful leaves
Rue anemone – also delicate white flowers, only in one place on the spicebush trail.  Worth hunting for!
Cut-leaved toothwort – also mostly done flowering, but a few are persisting

Plants that only biologists are likely to notice:

Chickweed – Chickweed grows especially well in damp, cool habitats, but it can tolerate and even thrive in a very broad range of moisture and temperature conditions. It is a native of Europe that has spread almost everywhere that Europeans have colonized (or maybe just even visited!). It is a cold tolerant annual that can, in areas with mild winters, persist all the way through the winter season. It grows in high latitudes (up close to the Arctic Circle) and at high altitudes. Its stems hang limply over the ground and are covered with small (1/3”), paired, oval leaves that open during the day and close at night. Rising over the greenery of the stems and leaves are tiny (1/2” across) white flowers whose five petals are so deeply divided that they look ten-pointed stars. Each flower only lives for one day and is capable of self-pollination (a very useful feature in a flower that opens weeks before most insects are stirring!). Chickweed, though, flowers almost continuously throughout its growing season and can on milder days be cross-pollinated by several species of flies. A single plant can make 2500 to 15,000 seeds! These seeds can germinate in the warming spring soils or persist in the soil systems for up to ten years without losing their viability. The seeds are eaten by many species of game and song birds, and the leaves are consumed by a wide range of mammals. Humans eat chickweed seeds and leaves, too, and brew plant parts into a variety of medicinal teas and poultices.

Purple dead nettle – this is another alien invasive plant that is widespread throughout our woods, fields, and lawns. It is also on a short list of plants hated by Carl Meyerhuber! Patches of purple dead nettle (called “dead” because it does not make the “stinging” chemical of its fellow nettle species) and ground ivy form ideal habitats for many small animals. In the past we have seen quite a few American toads and garter snakes hiding out under the protective cover of the dead nettle leaves.

And briefly:

Ground ivy (or as we prefer to call it, Gill-over-the-Ground) – small irregular purple blue flowers, ubiquitous!
False mermaid – looks like a weedy groundcover, but makes tiny white flowers – no one will notice this.
Yellow corydalis – small irregular yellow flowers, common
Small flowered crowfoot – small easy to miss flowers

Spring is racing into summer! Hang on!

Posted in Bill's Notes | 1 Comment

Signs of Spring 10: Crows and Jays

Photo by D. Sillman

Photo by D. Sillman

All winter I have had the same early morning routine seven days a week: I take my dog Izzy out for her morning walk somewhere between 6:30 and 7 AM. She has had her breakfast and is ready to reacquaint herself with the scents out along my street and, most importantly, do her “business.” Every coat I own has a stash of little blue, dog waste bags in their pockets! After a 15 or 20 minute walk about, I return Izzy to our glassed-in porch and take a bucket of black oil sunflower seeds, a scoop of shelled corn, and a triple handful of peanuts in the shell out to fill up the bird feeders. I have to do this every day because the deer come in every evening and eat any seed that managed to last the day. I try to balance the birds’ appetites with the portions I put out so that I don’t end up spending too much money feeding (really expensive!) sunflower seeds to deer!

When I go out with my seed buckets and peanut bag I always have a couple of acquaintances watching me. Up in a nearby red maple there is usually a crow staring down into the yard in silence, and up in the blue spruce tree that borders the front yard there is a blue jay who inevitably starts “pinging” his pure whistle tone at me.

Photo by D. Sillman

Photo by D. Sillman

I fill the feeders and dump the peanuts and go right back into the porch. I then let Izzy in to get her dog biscuit reward and look back out the window at the peanut pile. There is always at least one, sometimes three blue jays on the peanuts frantically stuffing as many peanuts as they can into their gular, throat pouches. They only have a few seconds before the look-out crow lands on the edge of the road and after a careful evaluation of the yard starts walking in toward the peanut pile. Usually a second crow lands and joins him just as he reaches the pile. They send the blue jays scattering.

The crows sit and methodically finish off all of the peanuts (unless the school bus drives by and scares them off. Then the jays might have another crack at the stash!).

I remember sitting at my writing desk four or five years ago watching a group of crows and blue jays argue about the fading winter and the coming spring. It was early April and the blue jays were probably starting their spring nests and the crows were checking out the nest area for some edible eggs. The racket was incredible! And, there were only four birds doing all of the high volume fussing!

Photo by D. Sillman

Photo by D. Sillman

Both crows and jays are members of the Family Corvidae. Corvids are known for their intelligence and for their wide ranging feeding habits. Although blue jays eat mostly seeds, nuts and insects, I have seen them pick robin hatchlings out of their nests and fly off with them. I have also seen them flying past with small eggs in their beaks. I have also seen crows acting even more aggressively than that! I have watched them knock cardinals out of the air and pounce on them. I have also seen them pick baby red squirrels off of tree branches as the squirrels walked along behind their mother. These feeding behaviors are some of the reasons that corvids aren’t widely loved birds!

Photo by D. Sillman

Photo by D. Sillman

Blue jays play a complex role in the avian community. Although they do occasionally at least eat other birds’ eggs and nestlings, they also serve as an early warning system for predators, especially hawks and owls. If a group of jays sees a hawk or an owl they scream their warning cries and then fearlessly mob the larger predator and drive it from their territory. This is a behavior that benefits not only the blue jays but also all of the other bird species in the area.

Corvids are also accomplished mimics and can not only pick up numerous calls and songs from their environment but also can be taught to produce many human words and even phrases. One sound that I frequently hear blue jays make is the call of a red-tailed hawk. What a fantastic tool to clear a bird feeder and, thus, have all of the seed to yourself! Once, high up on a nearby ridge, I followed the call of a red-tail through a dense copse of young red maple trees. After several minutes of hunting I finally spotted a bright, shining blue jay perched at the top of one of the maple screaming out over the valley like a hunting red-tail. I think that the sound and its echo were quite pleasing to him!

I have a great fondness for crows and can forgive them their predatory ways in appreciation of their amazing intelligence. Their ability to solve problems, devise hunting strategies and communicate those strategies among the individuals of their flocks are extremely impressive behaviors. Crows also recognize people and learn who are potential threats to them (like ornithologists who check on their nestlings or catch and band them! There was one well known ornithologist at Cornell had conducted an active, and somewhat intrusive egg count in the nests of the campus crows who was unable to walk across campus without being followed and harassed by mobs of angry crows!

Maybe crows even recognize those people who feed and care for them! My “morning crow” recognizes me and I am sure begins to anticipate the satisfying taste of breakfast peanuts as soon as he sees me come out to the feeder with my seed buckets! Although he’s too cautious to come any closer than the top of the maple tree while I am out in the yard, perhaps someday he will communicate with me more personally.

I will keep you posted!

Happy Spring!

Posted in Bill's Notes | 1 Comment

Signs of Spring 9: Bluebirds!

K. Thomas, Public Domain

Photo by K. Thomas, Public Domain

One of our great signs of spring is the return of eastern bluebirds to our field and edge ecosystems. A group of my students monitoring the birds on our campus through the winter and spring saw their first bluebird in early March long before the snows had started to melt or the temperatures had begun to moderate.

The eastern bluebird (Sialia sialis) is a small thrush that is also called the common bluebird, Wilson’s bluebird, and the American bluebird. It is six to seven inches long (smaller than a robin) with a wingspan of ten to thirteen inches and a slender, black beak that is well adapted to its predominantly insectivorous lifestyle. The brilliant blue of its wings and tail (males have entirely blue wings and tails, females are more gray with only the edges of their wings and tails colored blue) is the source of its name. Contrasting with the blue is its rusty-red chest and white abdomen.

In spring and summer eastern bluebirds can be found north and west into Saskatchewan and eastward to Nova Scotia in Canada. Their range then extends to the south all across the United States and into Mexico. They are bounded on the west by the Rocky Mountains. In winter, all of the northernmost birds and many of the middle latitude birds migrate into the southern United States, Mexico, and Central America. The bluebirds return to their northern ranges in March or April to establish their mating territories.

Photo by Sandyphotos 2009, Wikimedia Commons

Photo by Sandyphotos 2009, Wikimedia Commons

Bluebirds eat insects (about two thirds of their summer diet) and fruit. Beetles, crickets, caterpillars, and grasshoppers are some common insect foods. They primarily forage for their insects on the ground rather than snapping up them up in flight (like tree swallows, for example). Blackberries, raspberries, honeysuckle berries, wild grapes, dogwood fruits, and red cedar fruits are commonly ingested fruits.

Bluebirds prefer “savanna-like” ecosystems with open, grassy fields and scattered trees for perching and nesting. Edge ecotones between grasslands and forests are also highly preferred habitats. A wide range of tree types and ages is necessary to provide the birds with adequate tree holes and sheltered snags for nesting sites. This requirement has been frequently modified via the inclusion of human-made, bluebird boxes. Bluebirds seem to prefer sites near running water (creeks, streams, etc) in preference to sites near ponds, lakes, or birdbaths. This preference may be due to subtle differences in water quality between ponds and flowing streams or to the observation that flowing water freezes much later in the fall and winter and thaws much earlier in the spring.

Bluebirds are said to be monogamous, but many other “monogamous” bird species have been shown, after closer observation, to actually have very complex patterns of courtship, mating, and reproduction. It is likely that bluebirds, like many of the other thrushes, would also resist simple behavioral labels. Males establish a mating territory of 0.01 to 0.08 square kilometers after returning to their summer ranges in the early spring. Sometimes the males even begin building a nest in order to attract a female. Females arrive in the summer territories later in the season and are “wooed” by the males with songs, grooming behaviors, and offers of food.

Photo by K. Thomas, Public Domain

Photo by K. Thomas, Public Domain

Nests are typically built in a tree hole or snag (or in a fortunately placed bluebird box!). Ideally these nests are located high off of the ground and have narrow (one to one and half inch) openings into the nesting chamber. Location and entry hole size restrictions are essential protections against nest predators and parasites. Abandoned woodpecker holes are often chosen by a mating bluebird pair for their nesting site. The female will either entirely construct the nest, or, possibly, finish the nest begun by the male in his mating display. The nest will have an outer structure of coarse grasses, hay, and pine needles and an inner lining of softer grasses, hair, and feathers. Nest construction takes about ten days. Nests are only used once.

Females lay one egg a day for three to seven days for each of their broods. Here in Western Pennsylvania there can be two clutches each season (early spring and mid-summer) and incubation is between thirteen and sixteen days. After hatching, the female broods the nestlings for about a week and then joins the male in the Herculean task of gathering sufficient food for the rapidly growing nestlings. More than half of the gathered foods are insects. After fifteen days the nestlings are ready to fledge and very quickly after that are able to feed and care for themselves. At one year of age, the birds are ready to reproduce. Life spans of bluebirds in the wild possibly average six years for those individuals who successfully fledge but only about 65% of the eggs that are laid, actually yield successful fledges.

Bluebirds may be preyed on by bears, raccoons, and house and feral cats. Blow flies also frequently infest nests and nestlings. Nest predation by cats, chipmunks, and squirrels and also English sparrows and European starlings (two exotic, invasive species) cause substantial egg and nestling loss. The influx of the English sparrows and the European starlings along with the habitat spread of the nest parasite, the brown headed cowbird, are major reasons for the eastern bluebird’s numerical and distributional decline throughout the twentieth century. Human destruction of nesting and feeding habitats has also been a contributing factor to this decline. Human efforts to provide existing bluebird populations with suitable and secure nesting sites (“bluebird boxes”) have, however, been extremely successful in bringing this beautiful species back from the brink of extreme decline. The North American Breeding Bird Survey reports that since 1966 eastern bluebird populations have increased by nearly two percent a year! The Cornell Laboratory of Ornithology estimates the worldwide population of eastern bluebirds (80% of which spend at least some time in the United States) at 22 million individuals.

Photo by D. Sillman

Photo by D. Sillman

Deborah and I have recently joined a group up at Harrison Hills Park to monitoring a set of 38 bluebird boxes that were originally established in 2005. In 2006 observers counted 90 bluebirds fledged from the nests in these boxes! These boxes have not been repaired or monitored over the past eight so a group of volunteers led by Kristi Cihill and her husband Justin have jumped in to refit as many houses as possible and to watch and record the nesting and fledgling activity over the summer. I would like to call our group the “Cavity Nesting Team” since ALL native bird species who might utilize our nest boxes are going to be very highly prized. Tree swallows, nuthatches, chickadees, titmice, house wrens and Carolina wrens are all possible (if not likely) cavity nesters in our area whom we hope to see throughout the summer. The accompanying picture of four bluebird eggs was taken by Deborah last weekend at one of our boxes!

So, it’s bluebirds and more this summer! What a wonderful Spring has finally happened!

Posted in Bill's Notes | 1 Comment

Signs of Spring 8: Bald Eagles!

Photo by Frommer, Wikimedia Commons

Photo by Frommer, Wikimedia Commons

It is amazing that we can now refer to the bald eagle as one of “our birds” here in western Pennsylvania! In the early 1980’s when I moved here it was possible to find bald eagles (mostly up around Lake Erie) but they were very uncommon. In the past 5 or 6 years, though, mating pairs, year round residents, and overwintering groups have all been seen with great regularity all around our area!

I live in Kiski Township in southern Armstrong County and have seen bald eagles flying over my house, flying over the road on my drive to and from campus, and have heard them when I ride my bike down on the Roaring Run Trail. The drive over the Freeport Bridge almost always affords a good look at a bald eagle (or two) soaring over the Allegheny River, and last November Deborah and I spotted a perched eagle next to the Kiski River right across the street from the North Apollo Sunoco Station! They are becoming quite a regular occurrence (but are still a challenge to safe driving whenever they show up!).

Bald eagles were once a relatively common species in North America. Prior to European colonization it is estimated that there were 500,000 bald eagles in North America (about 7 times the number we have now). Every large river and lake had their resident eagles. By the early 1960’s, though, there were only 450 nesting pairs of bald eagles left in the lower 48 states!

The decimation of this species was due to multiple factors: habitat destruction, human encroachment, hunting, and ultimately the impacts of environmental pollutants (especially pesticides) on their reproductive physiology. But legislation and vigorous protection of bald eagles (via the 1940 “Bald Eagle Act” and its designation as an endangered species in 1967) has led to the resurgence of the species. There are now over 7,000 nesting pairs of bald eagles in the lower 48 states. In Pennsylvania there are 266 nesting pairs of bald eagles (compared to just 3 pairs 30 years ago!).

Photo by Majoros, Flickr

Photo by Majoros, Flickr

Bald eagle nests are great masses of sticks usually wedged together high up in a tree or on a rock cliff but occasionally even gathered together on the ground. The shape of the nest is determined by the geometry of the substrate: if it is in a fork of a tree you see a conical (“cylindrical”) nest. If it is on some flat branches (or on a flat rock or flat ground) you see a disk shaped nest. There are also “bowl shaped nests” and “inverted cone nests” and it seems however the branches go together is just fine for the eagles.

The average diameter of a bald eagle nest is 5 feet, and a pair will use the same nest for as many years as it holds together adding sticks each year to the mass. The largest bald eagle nest (which was a very old, often used one) was 9 feet in diameter and 13 feet deep. It was made up of 1.1 tons of sticks! And this was the largest tree nest ever recorded for an animal species!

Most nests last about five years. Usually the eagles select the largest, tallest tree in their territory. A view out over the water is required! Eagles complete for both nest sites and also the actual nest with hawks, crows and ravens.

The mating season for bald eagles runs from January to March. The mating pair engages in a wild, tumbling clutching flight/free fall that involves them flying to great heights, clutching each other via their talons and falling rapidly toward the ground. They break their grip just before hitting the ground and pull up out of the dive. It must be an incredible experience to see one of these mating clutches in person!

Bald eagles mate for life, but an eagle will take a new mate if an old mate dies. Bald eagle pairs don’t breed every year. I am sure that food resources and overall health of the partners play a role in determining whether a clutch of eggs will be laid or not.

Photo by HIldebrand, USFWS

Photo by HIllebrand, USFWS

Eggs begin to be laid 5 to 10 days after copulation. One egg is laid and then a few days later another, and then possibly a few days later one more. There is a 35 day incubation period and both the male and the female take turns sitting on the eggs. It can be a very tense and sometimes awkward moment when one of the parents tries to oust the other from the eggs. The resulting tussle can actually damage the eggs and even lead to a whole nest failure.

Eggs hatch in the order that they were laid, and it can take 12 to 48 hours for the hatchling to peck its way out of its egg. During the emergence period and for a number of days afterwards the female stays exclusively on the nest and the male works to keep her fed.
Many birds have this sequential hatching pattern and like many of these other species if food is at all limiting (too little food in the area or too inexperienced or inefficient parents to gather sufficient food for the nestlings) the oldest nestling will kill the younger. This “sibicide” seems very cruel (especially if you are watching it on a nest camera!) but it is a very efficient way to make sure that at least one of the nestlings will get sufficient food to grow and fledge.

The parents bring the nestlings prey, and they initially shred the carcasses and feed the raw meat to the eaglets. Eaglets grow incredibly rapidly (and therefore require immense amounts of food!). Growth rates of a pound every 4 or 5 days are typical. This is the fastest growth rate of any American bird.

Development is also rapid: at two weeks the eaglets can hold up their heads, at 3 weeks they are 1 foot tall and have adult size feet and beaks, at 4 to 5 weeks they can stand up and also can start tearing up their own food, at 6 weeks they are as large as their parents, at 8 weeks they start exercising their wings, and at 10 to 13 weeks they fledge. About 40% of the eaglets do not survive their first flight! And a little over half of all eaglets do not survive their first year! (that first step out of the nest is a real doozy!).

Photo Capture from Hays Eagle Cam

Photo Capture from Hays Eagle Cam

The development of small, durable, weather-resistant cameras has enabled researchers to closely monitor the activities inside of an eagle’s nest. The connection of these cameras to an Internet stream has further opened up this incredibly intimate view of bald eagle egg incubation and nestling/fledgling nurturing to the general public.

I tried to search around the web to find out exactly how many of these eagle cams are currently operating, but I wasn’t able to get a broad US-wide or World-wide count. To say that there are hundreds of them is probably reasonable estimate. A very popular eagle cam in our area is the Hays Eagle Cam down on the Monongahela River about five miles upriver from the point at Pittsburgh. The establishment of this camera reflects the amazing recent history of the bald eagle in our area.

Bald eagles returned to the rivers near Pittsburgh in 2012 possibly for the first time in nearly 200 years! There was a nest along the Ohio River and although that pair did not successfully produced a fledging, the next year (2013) another pair of bald eagles nesting in a small, fragile tree near Hays along the Monongahela River did successfully fledge an eaglet! This was the first eaglet born and fledged along the three rivers of Pittsburgh in two centuries!

The 2013 Hays nest fell apart that summer. In 2014, though, a second pair of bald eagles moved into the site and built a very substantial nest in a tall tree nearby. In that same fall Bill Powers of Pix Controller Inc with the permission of the PA Game Commission set up a nest camera on a nearby tree. In 2014 millions of viewers tuned into the Hays Nest Cam and watched the eagle pair incubate, hatch, nurture and fledge three healthy eaglets
This spring there have been a nesting pair of bald eagles on the Ohio River, another on the Allegheny River near Harmerville, and the Hays pair on the Monongahela. All three of Pittsburgh’s rivers have reproducing bald eagles! Unfortunately, a couple of weeks ago the Hays pair abandoned the nest after their second egg failed. There is always next year, though!

The Three River Eagles are back!

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Signs of Spring 7: Spring Peepers!

Photo by USGS (Public Domain)

Photo by USGS (Public Domain)

Last Thursday night it started to rain. The air became warm and humid and reminded me that we had not had a good rain in a very long time. The ground has been wet and muddy from snow melt, but it has been many months since a large, Gulf of Mexico air mass had eased its way across Western Pennsylvania. The rain continued into the early hours of Saturday morning and gave us a good couple of inches of water which we needed very badly. The rains also roused the spring peepers from the last of their hibernation hangover and stimulated them to start their nighttime choruses in the ponds and puddles all over western Pennsylvania. .

The spring peeper’s scientific name is Pseudoacris crucifer (which translates to “false locust” (for its insect-like call), and “cross” (for its distinctive X-shaped marking on its back). It is a small tree frog that lives around marshes, ponds, and temporary pools throughout the United States (except for the deep southeast). It is especially abundant here in the northeast. It has sticky foot pads that enable it to easily climb up the trees, shrubs, and tall grasses that surround its “home base” water source. It is from these perches that the male peepers sing out their distinctive, spring mating songs,

Photo by Z. Welty, Wikimedia Commons

Photo by Z. Welty, Wikimedia Commons

These mating choruses begin in early spring (around here usually in mid-March, but this year the first week of April) typically 15 minutes or so after sundown. The calls require a very large expenditure of energy by each individual which may explain why the males bunch together to form large, high volume ensembles (even though these groupings greatly intensify mating competition between individuals). Each frog is able maximally to make 90 calls per minute over a four hour chorus time. The mating/calling season only lasts for four to eight weeks. Male peepers begin to sing when they are three years old and the age, size, and overall health of the frog greatly affect the calling frequency. The temperature of the evening also affects calling patterns. On warmer evenings the frogs call much more frequently.

Females, attracted to the calling of the males, enter the calling area and select the individual with whom they want to mate. The male then clasps himself onto the female’s back and remains there as the female return to the water source to deposit her eggs. The attached male prevents other male from mating with the female and insures that all of the female’s eggs will be fertilized by his sperm. The female can lay between 800 and 1000 brown-colored eggs which may be deposited singly or in groups. Sometimes the eggs are set afloat in the pond water, sometime they are attached to submerged vegetation, or put into the mud, or into fluid filled tree hollows, or into many other types of available micro-pools.

Photo by Short Bus, Wikimedia Commons

Photo by Short Bus, Wikimedia Commons

The eggs take between six and twelve days to hatch. The larval frogs that emerge from the eggs (the “tadpoles”) are short with prominent dorsal fins. The tadpoles will remain in their aquatic form typically for ninety to one hundred days. This larval incubation can, however, be as short as forty-five to sixty days depending upon weather conditions, time of egg deposition, and conditions in the tadpole’s pool. Populations of peepers being reared in temporary pools may be undergoing selection for shorter and shorter larval incubation times. The devastating effect of the drying up of the pool is an unforgiving selection force. The tadpoles eat a wide variety of foods (including algae, dead vegetation, bacteria, fungi, zooplankton, flesh from animal carcasses, and even inorganic materials like sand). The tadpoles are in turn preyed upon by almost any organism that is larger than they are. Fish are especially significant tadpole predators in ponds, but predaceous beetles, salamanders, and water snakes also readily consume the tadpoles. Further, pesticides and other pollutants (including acid rain) are also significant agents of mortality in spring peeper tadpoles.

The metamorphosis of the tadpole into a frog begins with the appearance of hind limbs which is followed by the emergence of the forelimbs and the shrinkage of the tail. Jaws with teeth, eyelids, mucous glands in the skin, and finally the transformation of the light cartilaginous skeleton of the tadpole into the denser, bony skeleton of the frog complete the metamorphic transition into a tiny frog. The emergence of the frog onto land exposes it to even more predators and environmental dangers.

The frogs are readily eaten by snakes, turtles, birds, and mammals like chipmunks and muskrats. They are also frequently killed on roadways by passing cars and trucks. Peepers are also susceptible to many viral and bacterial illnesses, exhibit a wide range of benign and cancerous skin and mucous membrane tumors, and are beset by a wide range of endo- and ectoparasites (including tapeworms, flukes, nematodes, protests, and larvae of several dipteran species. Destruction of their aquatic habitats and even more subtle alterations of the forest cover around their wetland breeding sites can deleteriously affect the breeding potentials and survival of this small amphibian.

The spring peeper has been overwintering in an inactive, hibernative state under soil and leaf litter, in and under rotting logs, and even under rocks. They are frequently exposed to sub-freezing temperatures during their winter hibernation and are able to insure their survival in a frozen state by generating large quantities of glucose from their livers. This sugar (like we have seen in wood frogs and tree frogs) acts as a natural anti-freeze in their blood and other body fluids. Survival during these sub-freezing events is inversely related to the duration of the exposure (85% of the frogs survive after three days of freezing, about 50% survive after seven days of freezing, and 0% survive after twenty-eight days of freezing). While in hibernation, the peepers may also be preyed upon especially by small mammals active in the subnivian space beneath the snow cover. Shrews in particular readily consume the inactive, hibernating frogs. Long, cold winters, then, via extended lethal freezing and increased predation opportunities can have significant impacts on the population of this important sign of spring!

Fortunately, even after the long, cold winter we have all just endured, some of the peepers have survived. A chorus of peepers near campus has been heard singing at night, and several students have reported hearing other choruses near their homes. The chorus near our house in Armstrong County, though, has not yet begun to sing, although last night I did hear some tree frogs trilling. I hope that the winter has not been too hard on our local peepers!

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Signs of Spring 6: Tree Buds and Emergences

Photo by D. Sillman

Photo by D. Sillman

The silver maple tree at the bottom of my field flowered last week. The smooth lines of the branches that have been outline against the sky all winter are now fuzzy with the irregular edges of the tiny, open flowers. The red maples closer to the house, though, still have not flowered (although I understand from Jennifer Wood that some area bee keepers are starting to see bees returning to their hives with red maple pollen (and crocus pollen, too!)). In past years my red maples have regularly flowered by the third week of March. So this year’s very late appearance of their flowers is another sign of the stalled appearance of spring of 2015! The buds on the red maples, though, are swollen and look ready to pop open at any minute. We just need a couple of warm days to urge them on!

The tree buds are structures that encase and protect the embryonic flowers and leaves. The outer part of the bud is made of tough scales that form overlapping, shingle-like structures around the delicate leaf or flower growth tip. These bud scales keep out destructive insects and also insulate the inner tissues. These scales are really very tiny, very tough, modified leaves. Buds are classified as to whether they encase flowers (“floral” buds), or leaves (“vegetative” or, simply, “leaf” buds), or both floral and leaf embryonic tissues (“mixed” buds), and by their position on a branch (“terminal” buds are found at the end of a twig and “lateral” buds are found along the sides). On silver and red maple trees most buds are either floral or vegetative. The floral buds are larger and spherical and the leaf buds are smaller and more oblong. The floral buds are also typically clustered together in bunches on the twig. Over the winter I have watched squirrels nipping off the lateral buds on the red maple branches (they must be a welcome dietary supplement to balance out all of the sunflowers seeds they had been eating!). Most of the branches, though, were too thin for them to get out to the terminal buds, so I expect to see both flowers and leaves concentrated at the ends of tree branches this spring and summer.

Photo by M. Fistulosa, Flickr

Photo by M. Fistulosa, Flickr

As I said, the floral buds on the silver maple just opened last week and very soon, I hope, the red maple buds will open revealing the delicate clusters of red and yellow flowers. The tiny pollen grains from these flowers will then be spread mostly by the wind and by chance some will encounter ova in the ovaries of other flowers and accomplish the fertilization phase of the reproductive life cycle. The pollen is produced in prodigious amounts by these trees, and you can easily understand why. The probability of a given pollen grain, randomly dispersed through the atmosphere by the wind finding an appropriate ovum is infinitesimally small! To insure that fertilization occurs at all, the trees must fill the air with pollen. Human interactions with this pollen mass can generate allergic reactions in sensitized individuals. Hardwood tree pollen, in general, is a major spring allergy trigger. Dripping noses and red eyes, unfortunately, come with the season.

Once an ovum is fertilized it will develop into the maple tree’s distinctive winged seeds (their “samara”). These “maple keys” will, by early May or so, form great, fluttering clouds as they drop from the trees and become scattered by the wind across lawns and woodlots. Some of these seeds will germinate immediately while others may lay dormant in the soil until the following year. Many of these seeds will also be eaten by birds and squirrels. But these seeds and their seedlings are topics for a summer essay (and (great news!) summer is not that far away!)

Photo by D. Sillman

Photo by D. Sillman

What else is going on that could mean Spring is here? There’s some good news and some bad news, I am afraid. The bad news: deer ticks are active again! We have taken three off of our dog already and one off of our cat. The overwintering instars of the tick are up on the low vegetation and piles of sticks and leaves “questing” for passing warm blooded hosts. It is unlikely that the cold winter had any effect on the deer tick populations. Remember, if you get the tick off of you with 36 hours the chances of contracting Lyme disease stay very small, indeed.

Some more bad news involves some of the overwintering animals. Garter snakes, for example, are coming out of hibernation in spite of the lingering cold temperatures. Deborah and I found a small, dead garter snake alongside the Rock Furnace Trail last Sunday when we were out hiking. The snake was less than a foot long and quite thin, but didn’t have any external signs of injury. I think that had just crawled out of its hibernaculum and got caught in the developing cold of the day. I also found a very large fly cold to the point of immobility on the back bumper of my car! It must have woken up too soon, too. I don’t think that any of us will mourn the loss of a fly, though.

Photo by kquedquest, Flickr

Photo by kquedquest, Flickr

The good news includes the return of the killdeer to the area! We saw one over the weekend out in Allegheny Township and heard more when we walked in from the Penn State parking lot on Monday morning. The killdeer nest in the gravel on top of the flat roofed buildings here at Penn State New Kensington and act as “greeters” to anyone who dares to approach “their” buildings! We’ve also spotted more bluebirds on campus and there are so many robins that they have assumed their role as common birds! We are waiting for warblers, though!

Around my house the chipmunks are becoming very numerous (much to Izzy’s great delight!) and a group of red squirrels have begun to alternate with the army of gray squirrels at my sunflower feeders. I also saw my resident woodchuck dashing in and out of his burrow down in my woodlot, and spotted the pileated woodpecker making his feeding circuit between my black cherry trees. Yesterday afternoon I heard the male song sparrows start to sing, too. The stand of arbor vitae on the east side of the house is a favorite mating/nesting site for them! And, last night in response to a warm soaking rain the earthworms came up! (they had better dig back down into the soil, though, freezing temperatures are coming tonight!).

Ignore the snow. Spring is here!

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Signs of Spring 5: Waterfalls and Frogs!

Two Penn State professors at Ohiopyle, PA

Photo by D. Sillman

Rob, Michele, Deborah and I went to Ohiopyle last Saturday to see if there were any new (or different) signs of spring down there. In particular we wanted to see if the wood frogs that we saw two years ago (on a warm afternoon in late March 2013) might be back!

Frogs help to sing in the spring all over western Pennsylvania. The Spring Peepers (Hyla crucifer) will begin their group choruses as soon as we have some warm evenings, and the gray tree frogs (Hyla versicolor) will start their resonating trills soon after. The tree frogs may even continue to call through the rest of the summer! The first frog of spring, though, and the one we are looking for down in the cool, wet woods of Ohiopyle, is the wood frog (Lithobates sylvaticus). This frog neither peeps nor trills. Instead, it announces the start of spring by quacking like a duck!   Have a listen:

We walked out onto the Ferncliff Peninsula at Ohiopyle. The day was almost warm, and it felt good when the sun occasionally came out from behind the clouds. The first part of the hike was over the far shore’s rocks and boulders along the Youghiogheny River right at the Ohiopyle Falls. The picture above shows Rob and I working our way along the rocks and debris. The water level had recently been quite high! The debris layer extended well up onto the shoreline and made each footfall a bit of an adventure. The gray-green water was rushing past us and roaring as it went over the rocky falls.

Last week an unfortunate person slipped off of the rocks on the shore just across from us. He had climbed over a guardrail to pose for a picture not realizing that the rocks were covered with ice. He fell into the river, went over the falls, and has not yet been found. We stayed well away from the edge!

Back in the 1880’s this peninsula was the site of a large hotel and a thriving tourism/resort industry. In addition to the Ferncliff Hotel there had been a boardwalk, a dance pavilion, a bowling alley, tennis courts and ball fields all nested into the rocky terrain. Some of the foundations of these buildings are still visible up along the Fernwood Trail, but the peninsula has returned to a remarkably pristine, natural state. Fifty years ago the Western Pennsylvania Conservancy purchased the property of the peninsula and the surrounding hills and then sold it to the state of Pennsylvania to make the Ohiopyle State Park.

The isolated pools up and around the shoreline rocks were all barren of life. There were no insects, no amphibians and no growing algae. No signs of spring along the shore just the accumulated, plastic debris from the long winter.

Photo by D. Sillman

Photo by D. Sillman

The trail climbed up away from the rocks and headed out along one side of the peninsula. The deciduous trees were all bare, but the rhododendrons, hemlocks and the scattered white pines were a welcome green. Evergreen wood fern was scattered about in the undergrowth, too. It added a rich, green highlight to the overwhelming brown of the scattered, dead leaves.

We walked for a couple of hours around the peninsula but saw very little in the way of “spring.” No colt’s foot was blooming, no comma butterflies fluttered around the dense stands of rhododendrons. Everything was very quiet.

Just before the trail junction where Fernwood Trail split off from the Ferncliff Trail there was a ten meter by ten meter fenced off area designed to keep white tailed deer away from the developing tree seedlings. Inside the fence margin poplar and birch seedlings grew in incredibly dense clusters. There must have been two hundred, three and four foot tree seedlings growing inside the fence (there were hardly any outside the fence)! The woods would look very different if there were no white-tailed deer!

Michele and Deborah took the Fernwood Trail while Rob and I continued on the Ferncliff Trail, but everything was very quiet until we got the end of the trail. Deborah and Michele were waiting for us (they walk a lot faster than Rob and I!). They had found frogs!

Photo by D. Sillman

Photo by D. Sillman

We climbed up to the Great Allegheny Passage Trail and followed it back toward the town. Near the trail parking area a small, vernal pool was alive with a couple of dozen wood frogs. They splashed and quacked and made us feel very welcome!

The wood frog is found from northern Georgia all the way up to far northern Canada. In fact, it is the only “cold blooded” vertebrate known to live north of the Arctic Circle! They utilize temporary pools formed by spring rains and snow melt as breeding pools and then spend most of the rest of their active season away from standing water. Adult wood frogs feed opportunistically and extensively on small insects and other invertebrates. They use their long, sticky tongues to capture prey and are said to eat “anything that they can fit into their mouths.”

The ability of the wood frog to survive in high latitude ecosystems depends upon a number of specialized physiological adaptations that include the presence of specific proteins in the blood that regulate ice crystal formation, circulatory controls that shunt blood preferentially into critical organs (heart, liver, brain), and a liver response that releases huge amounts of glucose into the blood stream and organs. These high levels of glucose act as a cryoprotectant which reduces the amount of ice formed in the protected tissues and cells.

During hibernation, 60 to 70% of a frog’s body fluids may be frozen. Cardiac function stops and blood ceases to circulate. As their bodies thaw, their hearts resume contractions and their livers rapidly clear the high levels of glucose from the blood even before all of the body’s ice is melted. Thawing frogs display some short term movement and behavioral difficulties but are soon fully functional.

We watched a couple of frogs jump out of the dense piles of leaf litter that surrounded the pool. It was like they were catapulting themselves out of hibernation! They flung themselves into the increasingly crowed water, and you could almost hear them shouting, “I’m back!!”

In the mating pools, males call to females with their “duck-like” songs. An attracted female enters the pool and is quickly grasped on the back by the smaller male (this is called “amplexus”). The male may remain in place on the female’s back for 24 to 72 hours. The male releases sperm into the pool water as the female ovulates and thus externally fertilizes the forming egg mass. A typical egg mass contains 1000 to 2000 eggs. The female moves the floating egg mass into the shallow areas of the pool in a large, communal raft. Counting these rafts in an area’s pools is an accepted, and highly efficient, way to determine the population density of the wood frog in a particular region.

Both the fertilized eggs and the developing embryos can withstand even prolonged sub-zero temperatures. The ”jelly” that surrounds them and holds the great floating masses of eggs together helps to pull water out of the egg or embryo when it freezes. This prevents freeze damage to the delicate cells. It will take quite a while (two and a half months) for the embryos to develop into tadpoles!

So, spring IS happening out in the woods! Just ignore the snow that’s in tonight’s forecast!

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Signs of Spring 4: Termites

Photo by S. Bauer, USDA

Photo by S. Bauer, USDA

When Deborah and I were in graduate school at the State University of New York College of Environmental Science and Forestry in Syracuse (better known as SUNY-ESF!), Deborah, as a student in entomology, took the graduate level, insect taxonomy course. One aspect of the course was for each student to put together an insect collection. To make it interesting, the instructors promised to reward the best insect collection (as measured by the largest numbers of types of insects) with a bottle of wine (ah, grad school!)). Deborah dug into the collecting and pinning and displaying of her insects with great enthusiasm. There was one thing, though, that was holding back her collection diversity: there were no termites in upstate New York! The long, very cold winters prevented colonies from becoming established.

Termites, back then, were classified in their own insect order called “Isoptera.” It was important for the diversity and quality of the collection to have representatives from as many orders of insects as possible. I have just learned, however, that this classification may not be accurate any longer. It turns out that termites are evolutionarily closely related to cockroaches and are now included as a mere sub-order or super-family within the Order Blattodea! (Deborah had, mostly from living in a series of college-level apartments and houses, MANY representatives of Blattodea in her collection!).

Anyway, back to the comfortable past when termites were termites and not relatives of roaches! In order to add to a little polish to her collection diversity (and, eventually, to allow her to win that bottle of wine!) she asked a friend who was going to visit his family in (where else?) Pennsylvania, if he would mind looking around in some decaying logs or crumbling houses to find her a few termites. Pennsylvania, as many of us who live here know, is an ideal habitat for termites.

So we flash forward twenty years and Deborah and I are living amongst the termites here in Western Pennsylvania. We had seen termites in downed logs in our woodlot and orchard, and they had even shredded up some wooden posts I had used when building our dog-yard fence. They seemed, though, to be keeping their distance from the house, and almost every time I see one I think of having a nice glass of wine! Then one afternoon in our dining room, I picked up a cardboard box full of teaching handouts and cardboard cut outs of insect body parts and legs and wings, of all things, and was surprised to see movement in the box and shredding of the edges of the cardboard. We followed a trail through the gaps in the flooring down into the basement where we saw the characteristic, packed soil tubes (pictured below) of our local termite colony etched into the wood of the floor joists and extending out through gaps in the foundation. We, of course, reacted like good biologists …. actually not, we were horrified that our house was under attack and looked around for poison, any poison that we could use to dispatch the invaders.

Photo by J. Conrad, Public Domain

Photo by J. Conrad, Public Domain

We calmed down and called a termite service and signed up for a long-term, non-pesticide termite control system. Traps were placed out around the east side of the house where the termite activity was greatest. In the traps were bits of wood of a type that was proven to be irresistible to termites (the technician wouldn’t tell us what types of wood it was. He said that it was a company secret). The plan was once the termites started munching on the wood in the traps, a chemical that acted as an anti-reproductive hormone would be introduced into the wood chips. The feeding termites would take this hormone back to their main nest where the entire colony would be subsequently neutered and destroyed.

It took over a year and a half for the termites to find and begin to chew on the “irresistible” wood chips. During that time we didn’t see any more termite activity in the house (we also didn’t put anymore cardboard boxes of papers on the floor next to the east wall of the dining room!) The technician applied the hormone and we continued to see no termite activity through the remaining two years of our contract, and we have continued to not see any termites in the house for these past 18 years (although the fallen branches of the apple and pear trees in our orchard (about 30 feet to the west of our deck) are quickly degraded and decomposed by termites. I think termites REALLY like apple wood! Maybe I should pass that observation on to the termite control company!

The termite technician told us that there was a great deal of termite activity all along the towns of the Kiski River Valley. He said that they speculated that there was, in fact, one gigantic colony of termites that were feeding on the fallen wood (and standing houses) of Apollo, Vandergrift, and Leechburg. The image of a vast, highly interconnected super-colony humming along just beneath the surface of the soil was both exciting and horrifying (depending on whether I was thinking like a biologist or a homeowner).

A recent article in the New York Times (which Lisa Meyerhuber passed along to me) talked about the importance of tropical, African termites in generating a soil structure that not only resists wind and water erosion but also retains a large percentage of a site’s annual rainfall. In desert ecosystems this water retention along with the very fertile accumulation of termite feces can make the soil around termite mounds into an oasis that can support vegetation and animal life far above levels seen in the nearby, non-termite worked soil.

Photo by BBC.co.uk

Photo by BBC.co.uk

There was another African termite story a few years ago, too. In the Namib Desert of western Africa the sparse vegetation grows in great rings that can be forty feet across with extensive areas of barren soil areas in between. This odd and visually compelling plant growth pattern was finally explained as the consequence of subterranean, sand termites feeding on plant roots and altering the soil around them to divert and retain the scant rainfall of the Namib into ring-shaped micro-reservoirs. Plants then could grow roots into these micro-reservoirs and, thus, ended up growing in these unusual and very persistent rings. This explanation is quite pleasing on an ecological level but pales in scope and terror next to the native, Himba people who felt that the plant rings were either the footprints of gods that had walked across the desert or relics from the poisonous breath of a giant dragon that lived underground out the Namib.

So, are we sitting on top of a giant termite colony here in the Kiski Valley? Are these termites working the soil into a high level of fertility and stability? Is it worth putting up with a little structural damage (and cost) to have these social insects do their wood decomposition and soil burrowing activities?

What wonderful questions! Or should we look around for some dragons?

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