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!

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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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Signs of Spring 3: The Great Backyard Bird Count

Photo by D. Sillman

Photo by D. Sillman

A month ago (February 13th) the Cornell Laboratory of Ornithology, Birds Studies Canada and the National Audubon Society sponsored a three day, “citizen’s science” project called “The Great Backyard Bird Count.” This world wide count of birds began in 1998 and has grown in scope and participation with each passing year. Participants are asked to spend fifteen minutes either stationary at some observation point or walking through a habitat counting and identifying the birds they see. Online checklists developed by eBird facilitate the reporting of these observations, and the compilation of the data from the observers seems to be nearly instantaneous!

Here is the link to read this year’s report: http://gbbc.birdcount.org/2015-gbbc-summary/

Some highlights of this year’s count include the total number of checklists submitted (147,265) and the total number of people submitting one or more checklist (143,941). A total of 5,090 species of birds were identified and 18, 726,079 birds were counted! This was, indeed, a very robust survey of birds!

There was a distinct North America bias to this count since about 74% of the checklists came from the United States. The ten most frequently mentioned species on the lists were all North American species (led by the northern cardinal (pictured above) and the dark-eyed junco), and all but one of the top ten most numerous birds in the count were also North American species (the 1,494,937 snow geese topped this list!). The third most numerous species in the count, though, was an Eurasian bird called a brambling.

Photo by M. Szczepanek, Wikimedia Commons

Photo by M. Szczepanek, Wikimedia Commons

Bramblings (Fringilla montifringilla) are small finches that summer and breed in the northern forests of Asia and Europe. They then migrate south for the winter (to southern Europe, or northern Africa, Pakistan, India, China or Japan) in large flocks that can number over a million birds. One of these flocks was counted by a Great Backyard Bird Count checklist observer in Germany! The one million birds that this individual estimated the flock of bramblings to number pushed the species (with a total count of 1,000,047) to position number three on the abundant list (well above the 630,610 European starlings!). I think that this reflects the power of the individual even in such a high participation endeavor!

Photo by D, Daniels Wikimedia Commons

Photo by D, Daniels Wikimedia Commons

The 2015 count also revealed some interesting changes in the abundances and distribution of many bird species. One species, the pine siskin (Spinus pinus), showed up on 10.5% of the Great Backyard Bird Count checklists this year compared to only 1.2% of the lists from last year! Locally, Lynn Ramage in Armstrong County counted twenty pine siskins at her bird feeders! This “eruption” of pine siskins may be related to the cold, harsh winter which drove the birds slightly further south than usual (right into the heart of the Great Backyard Bird Count observers!), or it may be related to some as yet unknown population cycle in this species. In science, observations lead to explanations and model building, and then experimentation and model re-formulation! I did not see any pine siskins during my counting periods. Possibly, this was due to the fact that several weeks previously I had taken down my thistle (“nyjer”) feeder for cleaning and repair and had yet to put it back up! The pine siskins do love their thistle!

Pennsylvania was second only to California in total number of checklists submitted to the count. Allegheny County led the long list of participating Pennsylvania counties with 101 species and 626 submitted lists. Locally, Westmoreland County submitted 148 lists and counted 68 species, Armstrong County submitted 37 lists and counted 45 species, and Butler County submitted 133 lists and also counted 45 species.

So what is accomplished by this Great Backyard Bird Count? Tracking the pine siskins is interesting. Tracking the southward eruption of the snowy owls is exciting (check out the website!), and just knowing how many birds are out in our wide ranging habitats is important. But maybe most important is getting all of these people outside all at once to look at birds! That is the payoff that is priceless!

The species that I counted for my two Great Backyard Bird Count lists were as common as could be. They all made it onto to top ten “most frequently listed” species. My birding experience didn’t range into wild, exotic discoveries. My birds were cardinals, juncos, blue jays, titmice, chickadees, and crows, and I was very pleased to see them!

Some years ago I was giving a talk at a conference about Deborah’s and my Virtual Nature Trail and the actual, physical nature trail on our campus that was the inspiration for it. At the end of my presentation I was asked a question, “what was special, or unique about this nature trail?” I sensed an undertone to the question of “why would anyone want to go see this trail?” Usually you come up with answers to questions like this much later, but somehow I found the answer right away: There is nothing particularly unique or “special” about this trail, and this is what made it so important. It is the beauty in the ordinary, as Bill Bryson once put it “the low level ecstasy” of the common species and common terrain that make this site so wonderful. Sitting back and seeing what is around you in nature always elevates and inspires you!

And, to me, this is what makes the Great Backyard Bird Count and the sight of all of those ordinary birds that every day gobble down my sunflower seeds, corn, peanuts and thistle, so amazing.

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Signs of Spring 2: Looking for Spring

I have been reading back over some of my “Signs of Spring” from previous years to try to get ideas about the right places to look for hints of this year’s elusive spring. There has to be some positive things happening around us even in this interminable winter!

S. Williams, Flickr

S. Williams, Flickr

My first stop was my glassed-in, front porch on a sunny afternoon (outside air temperature was ten degrees). I looked for any ladybird beetles coming out from behind the aluminum siding, but they weren’t buying the day’s feeble attempt at spring-time warmth. I even looked inside the folded deck umbrellas and in the stack of empty birdseed bags for some active, brown marmorated stink bugs (how desperate is that?), but they weren’t ready to wake up either. I did find one walking stink bug on the wall in the inside hallway of the house. I dealt with him via the O’Hara Method (see blog on October 3, 2014).

I have been alert in the early mornings for the smell of skunk knowing that the males start wandering about in the middle to late winter looking for mates. My old dog Kozmo used to be a master at finding these early skunks (he just couldn’t help himself, I guess). I did come up with a very good recipe for de-skunking a dog, though, thanks to all of the trial and error opportunities he provided me. If anyone needs it, I am happy to share. Izzy has yet to see a skunk, and neither of us has detected any fresh scent out under the bird feeders or in the side yard.

Photo by D. Sillman

Photo by D. Sillman

The gray squirrels are acting increasingly goofy around the bird feeders. One of the squirrels will suddenly break away from its obsessive gorging on my (really expensive!) black oil sunflower seeds and start chasing one of the other squirrels around the yard. They go over and around the heated bird bath, and then up the front spruce tree. They are just saying “hello,” I am sure! We’ll watch their “winter-born” litter grow up this summer. So many more squirrel mouths to feed!

In the early morning while walking Izzy I hear the male cardinals doing their “birdie-birdie-birdie-birdie” songs all the way to completion now. Even on the very cold mornings the males are singing at each other trying to emphasize how fit they each are and that their genes are something to be greatly desired! How they can be so energetic without coffee, though, is beyond me.

The female sharp-shinned hawk has not yet come to the top of the gnarly black locust tree out back to screech for her mate. I am sure that if they are going to have any eggs this year they have at least started their courtship rituals, but the afternoons out back have been quiet. I found several blood and feather spots in the snow out and around my yard and field. The sharp-shins are preying on the feeder birds. From the feather piles I infer that they mostly take doves and cardinals.

The usual time for the robins to return to southern Armstrong County is the middle of February (usually the 13th or 14th of the month). This return date has been very consistent over the 25 years that I have been watching. There is no sign of them around my house yet this year, though. Too much snow and ice covering all of the places where the earthworms hide! It’s just been too cold for them to ease them out of the sheltered valleys and woodlots. I am very happy to report, though, that my Ecology students who are surveying the birds on campus saw a robin and several male bluebirds last Tuesday! They were down at the edge of the Nature Trail woods at the end of the soccer field. Soon the big flocks will arrive!

Photo by D. Sillman

Photo by D. Sillman

Spider, my box turtle has also kept his head down (or in his shell, as it were). He has moved about a bit on our few sunny days but has not taken up his “feeding” pose where he stretches out his surprisingly long neck to stare up at the top of his terrarium (food always drops in from above!). He is not thinking of strawberries and earthworms yet, but I do wonder what his winter dreams are like!

So, everything is really waiting. The signs of spring will all wash over us all at once just as soon as these arctic air masses stop pouring across us and the warm, humid Gulf of Mexico air starts its northward push. Those winds from the south will blow the migrating birds our way and the warm air will trigger the leaf buds to open and the flowers to bloom. Everything will happen all at once!

I am going to go out to the campus nature trail this week to see if the skunk cabbage has melted its way up through the snow yet. I’d rather be seeing flocks of robins and the blooms of crocuses, but I’ll take the skunk cabbage if that is all that I can get!

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Signs of Spring #1: Monarchs Waking up in Michoacán!

Carolina wren (photo by D.Pancomo, Wikimedia Commons)

Carolina wren
(photo by D.Pancomo, Wikimedia Commons)

I have wanted to start the Signs of Spring but have not “seen” very many hints that this long, cold winter was ready to give way to warmer, greener days. There are a few birds singing when I take my dog, Izzy, out for her 6:45 am walk. Titmice are pinging out their two note patterns, Carolina wrens (who have sung all winter!) cycle through their four phrase whistles, and northern cardinals make starts at their pulsating, territorial songs from the tops of the surrounding spruce and maple trees. These birds are already thinking about mating. What could be a bigger sign of spring? The blue jays are also pinging and screeching at me but they are just demanding their morning piles of peanuts and shelled corn. Another observation of the approaching spring is that it is not pitch dark at 6:45 am. I don’t have to carry a flashlight or risk being blinded by passing cars’ headlights as I walk along the roadside. We have added an hour and forty minutes to our daylight since the winter solstice on December 21. Sunrise is happening 40 minutes earlier than it did during our darkest day. Now, all of this is important, but it doesn’t quite feel like enough to start our observations of spring.

Photo by R. Kumra, Wikimedia Commons

Photo by R. Kumra, Wikimedia Commons

So, instead, I am starting with a thought experiment: I am imagining that I am in the coniferous forests of the mountains in the states of Mexico and Michoacán in south-central Mexico near the town that our good friend and former teaching colleague, Maria Franco, grew up. The branches and the limbs of these tall trees are covered with the orange and black bodies of millions of hibernating monarch butterflies, and right about now these butterflies are starting to wake up! Great clouds of monarchs are swirling around in the air!

The monarchs that have been sleeping away the winter in these Mexican forests are nearing the end of their nine month long life spans. They are starting to fly to the north drinking nectar from the early blooming flowers and mating along the way. They may get as far as Texas or Oklahoma where, hopefully, their arrival will coincide with the emergence of this season’s milkweed plants. The females will then lay their three to four hundred eggs on the milkweeds (spreading the eggs out over a large number of plants) and the overwintering generation will die.

The eggs will hatch in three to five days depending on the temperature. The emerging larvae feed first on the egg capsule and then begin to eat the milkweed leaves. They will molt five times during this larval life stage and increase their body mass more than two thousand times. The eggs and the larvae (the “caterpillars”) are under intense predation and parasite pressures. More than ninety percent of the eggs and caterpillars will fail to survive. Eggs will be eaten by ants, earwigs and snails, and larvae will be eaten by beetles and other insects (like paper wasps) or killed by parasitoid wasps, bacteria, or fungi. Since the larvae feed exclusively on milkweed leaves they accumulate the milkweed’s cardeolides (a cardiac glycoside that can cause the heart of a vertebrate to stop its contractions!) in their body tissues. These cardeolides make the larvae (and, eventually, the adults) poisonous to most vertebrates. Relatively few monarch caterpillars or adult butterflies, then, will be consumed by vertebrate predators.

Photo by T. Hall, Flickr

Photo by T. Hall, Flickr

The end stage caterpillar then forms a cocoon (“chrysalis”) within which the tissues and organs of the larvae dissolve and are reformed into the structures of the butterfly. This metamorphosis takes between nine and fifteen days. The emergence of the butterfly from the chrysalis stimulates mating and a drive to fly on toward the northeast. New adults repeat this mating, feeding, and egg laying cycle several times through the summer until seasonal conditions or some innate developmental cue triggers the adults to turn around, forgo mating, and then start the long trip back to the mountain forests of Mexico.

The above cycle is characteristic of the very large monarch population that is east of the Rocky Mountains. Almost all of these butterflies overwinter in the coniferous forests in the mountains of Michoacán and Mexico. This round trip migration to and from this very specific overwintering site in Mexico covers several thousand miles. The monarchs that live in the smaller area west of the Rockies, on the other hand, overwinter in in coastal sites in Southern and Central California. Their migratory route only measures hundreds of miles at the most. In both overwintering sites, however, the numbers of monarchs covering the trees and shrubs while they wait out the winter months in their inactive, diapause states can be truly staggering!

There are some recent observations about the long-distant, migrating, eastern monarchs. One involves the impact of the long, fall migration to reduce the parasite load of the butterflies’ population. A serious, protozoan parasite (Ophryocystis elektroscirrha) that infects monarchs is eliminated when they undergo the strenuous migration all the way to the forests of Michoacán (because infected individuals do not survive the migration!). When the monarchs bypass the long migration (by selecting to overwinter in forests of southern United States (like in Barbara Kingsolver’s excellent novel “Flight Behavior”)) or when they linger too long at planted patches of tropical milkweed (which does not undergo a seasonal die-back like the temperate milkweed species), then they do not select out individuals carrying the parasites possibly with disastrous results (results that could include annihilation of the entire overwintering population!).

The trip to Mexico, then, is built into the health and fitness of the entire monarch species! Maria has promised Deborah and I that she will take us to Mexico to see the monarchs in their forests. A great January trip that will feel like a dream!

So, on this cold, wintery day I am not looking at the ice and snow around me. I close my eyes and I am in Michoacán with the monarchs. It is a glorious sign of spring!

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Signs of Winter 12: Blight Resistant American Chestnut Trees! (go, Stumpies!!!)

Forest History Society

Forest History Society

Last week I wrote about the emerald ash borer and its devastating assault on our eastern forests. In that essay I mentioned the America chestnut and the terrible blight that attacked it over one hundred years ago. American chestnuts were once one of the most abundant trees in the eastern United States. They were not the tallest tree in the forest, but they did have huge trunks that could be ten or twelve feet in diameter and thick, extending, shading branches that spread out over remarkably large areas (Photo of virgin American chestnut trees used with permission from the Forest History Society).

The American chestnut (Castanea dentata) also produced large numbers of extremely palatable nuts that were eaten not only by squirrels, birds, deer, and bears but also humans. The American chestnut made these nuts in abundance every year (unlike oak trees, say, that make their acorns over multi-year, boom and bust cycles). Many animals relied on the yearly production of chestnuts to sustain their populations.

Photo by B. Marlin, Wikimedia Commons

Photo by B. Marlin, Wikimedia Commons

In 1904, though, the American chestnuts lining the roads and walkways of the Bronx Zoo began to sicken. Their leaves withered and great lesions appeared in their bark. The trees then died one by one. They were the first recorded casualties of Chestnut Blight epidemic that swept through the eastern United States. There is evidence that the fungus responsible for this disease (Cryphonectria parasitica) had been present in the southern U.S. since the 1820’s, but the death of the chestnuts in New York set off alarms that reverberated through the country. By 1950, the American chestnut was for all intents and purposes “gone.” It was no longer a reliable source of nuts or timber. It was no longer a tree of size and majesty.

The species, though, persisted even in the face of this awful disease. The fungus can be transported either via insects or on the wind and infects a tree through cracks in its bark. The fungal mycelia then grow into the cambium layer of the tree (the part of the tree that includes the vascular system that transports sugars and nutrients). The tree responds to the infection by sealing off the infected cambium with a dense, callus tissue. But the fungus grows faster than the callus and eventually the tree loses its ability to transport nutrients and dies. The fungus, though, does not affect the tree’s roots, and new chestnut trees are then able to sprout from the still living roots and stumps. Depending upon the site density of the chestnut trees and the abundance of the fungal spores, these new sprouts may grow for ten to fifteen years before the fungal infection kills them. They can reach heights of fifteen to twenty feet and can even produce nuts for several years before they die back. This growth and die-back cycle has caused the American chestnut to become more of a shrub than a tree!

All this, though, might be changing dramatically. Two researchers (Bill Powell and Chuck Maynard) and their teams at one of Deborah’s and my alma maters, the State University of New York College of Environmental Science and Forestry (SUNY-ESF) (a college whose students are affectionately referred to as “Stumpies!”) have unveiled a viable and thriving, transgenetic American chestnut that is resistant to the fungus that causes chestnut blight. They are waiting for final federal review and approval so that they can begin planting these trees back into the forests of the eastern United States.

Photo by J. Grandmont, Wikimedia Commons

Photo by J. Grandmont, Wikimedia Commons

How they developed this hybrid tree is simple to explain but astoundingly complex in its actual accomplishment. Some forty years ago researchers at another institution noted that strains of pathogenic tree fungi that produce low levels of oxalic acid are far less virulent than the strains that produce high levels of this acid. So the researcher team at SUNY-ESF isolated a gene from wheat plants that codes for an enzyme (oxalate oxidase) that breaks down oxalic acid and inserted it into the genome of the American chestnut tree. It turns out that wheat and many other grass species use this oxalate oxidase as a generalized protection against their own fungal infections, and it further turns out that this enzyme is equally as effective as a fungal control agent in the transgenetic chestnut tree! The chestnut blight fungus makes large amounts of oxalic acid at the margins of those calluses (or “cankers”) that the chestnut trees make to try to seal the fungal infection off from the tree’s healthy tissues. The acid eats away the wall of the protective callus and allows the fungus to then run riot through the tree’s tissues. Breaking down the oxalic acid at this margin not only neutralizes the erosive tool of the fungus but also, via the impact of the hydrogen peroxide that is being generated as a consequence of the catalyzed oxalic acid oxidation, strengthens the lignins in the wood of the callus! The callus, then, very effectively seals off the blight fungus and the tree remains healthy!

The Chinese chestnut tree and other Asian varieties are resistant to the chestnut blight fungus through other genetic mechanisms, but it turns out that the transgenetic American chestnut with its oxalic oxidase enzyme and lignin enhanced calluses is even more resistant to the fungus than those Asian chestnut species to this disease!
The final phase of this SUNY-ESF project is to raise and plant ten thousand of these blight resistant, transgenetic American chestnut trees. This past fall, to raise funds for this effort, the Development Office of SUNY-ESF set up a crowd funding campaign called the “Ten Thousand Chestnut Challenge.” They sent emails to SUNY-ESF alumnae and to past donors to the college hoping to raise the fifty thousand dollars needed to cover the costs of this tree production program. In the four brief weeks of the campaign, they exceeded their goals and raised over one hundred and four thousand dollars!

Photo by N. Tonelli, Flickr

Photo by N. Tonelli, Flickr

A benefit of becoming a contributor to this chestnut tree crowd funding challenge was that you received a small bag of American chestnut tree seeds as a token of thanks. These seeds are not for the transgenetic, blight resistant American chestnut, but instead are from a genetically diverse array of wild American chestnut trees. The trees grown from these seeds will serve as “Mother” trees that will be crossed with the transgenetic chestnuts to greatly expand their genetic base! My zip-lock bag of chestnut seeds are in the salad crisper of my refrigerator getting their three months of “winter weather” so that they will germinate when planted in the spring. I will share pictures this summer!!

If you want to read more about this fantastic research and rehabilitation effort, check out www.esf.edu/chestnut . Happy winter, everyone, and happy chestnut forests!

Go, Stumpies!!

Posted in Bill's Notes | 2 Comments