Signs of Summer 4: The Curious Case of the Missing Gulls

MS Vandeem (Photo by D. Sillman)

MS Vandeem (Photo by D. Sillman)

From Arthur Conan Doyle’s Sherlock Holmes story “Silver Blaze:”

Gregory (Scotland Yard detective): “Is there any other point to which you would wish to draw my attention?”

Holmes: “To the curious incident of the dog in the night-time.”

Gregory: “The dog did nothing in the night-time.”

Holmes: “That was the curious incident.”

Halifax Harbor (Photo by D. Sillman)

Halifax Harbor (Photo by D. Sillman)

From the deck of the MS Vandeem cruising down the St. Lawrence River:

Fellow Cruiser: “Is there any other point to which you would wish to draw my attention?”

Me: “To the curious incident of the sea gulls.”

Fellow Cruiser: “But there are no sea gulls.”

Me: “That is the curious incident.”

In anticipating our cruise down the St. Lawrence I prepared myself for two ecological experiences: 1. I anticipated seeing great flocks of sea birds (especially sea gulls) all along the river and estuary, and 2. I anticipated seeing whales (13 species of whales (from belugas to blue whales) spend their springs and summers in the St. Lawrence River and Gulf!). Amazingly, though, there were almost no seagulls or other sea birds to be seen over the week of the cruise, and the only whale we observed was a harbor dolphin that Deborah spotted in Bar Harbor, Maine! The whales might have been avoiding the noise and fuss of our large cruise ship (The MS Vandeem), but sea gulls, based on my experiences along the Texas Gulf Coast and the Virginia mid-Atlantic coasts, should have been drawn to this boat and to the various port towns we stopped at like flies to a picnic!

Where were they?

Ring billed gull, Photo by D. Daniels Wikimedia Commons

Ring billed gull (Photo by D. Daniels Wikimedia Commons)

Background reading about the birds of eastern Canada listed four main sea gull species: the ring-billed gull (Larus delawarensis), the herring gull (L. argentatus), the great black-backed gull (L. marinus) and the black-legged kittiwake (Rissa tridactyla).  The great black-backed gull and the black-legged kittiwake are most frequently found to the north and to the seaward sides of the places we were scheduled to visit (they are true seas dwelling gulls, not, as my cousin Amy recently pointed out to me, bay dwelling “bagels!” (Happy retirement, Amy!)), so my expectation was that we would see quite a few ring-billed gulls (they were estimated to make up 80% of the gulls along the St. Lawrence) and herring gulls (estimated to make up 10% of the St. Lawrence gulls). In fact, the largest single breeding colony of ring-billed gulls was quite close to where we boarded the Vandeem just east of Montreal (on the Ile Deslauriers: a colony of 51,000 pairs of birds!). Unfortunately, we could not see this island from the deck of our boat!  We did see several great blue herons (Ardea herodias) flying over Montreal and down the St, Lawrence just before we boarded the Vandeem, but not many other birds at all!

Herring gull Photo by D. Daniels, Wikimedia Commons

Herring gull Photo by D. Daniels, Wikimedia Commons

Along the Quebec stretch of the St. Lawrence we saw a handful of herring gulls but no ring-billed gulls. When we docked at Quebec City, there were no waiting flocks of gulls of any kind to greet us as we disembarked from the boat. As we continued down the St. Lawrence from Quebec City and headed out into the Gulf of the St. Lawrence, we saw a few more herring gulls, a couple of ring-billed gulls, and a pair of common terns (Sterna hirundo). When we docked at Charlottetown, Prince Edward Island (or Sydney or Halifax, Nova Scotia) there were also no flocks of gulls, no great flying commotion greeting us on the docks.

In Charlottetown we sat out on a dockside table and had several baskets of steamed mussels and clams (and a very fine local ale). We watched two double crested cormorants (Phalacrocorax auritus) stand to dry themselves out on some old pilings in the harbor but were neither entertained nor pestered by any gulls. We had a similar experience on the waterfront boardwalk in Halifax (in Sydney it was far too cold and wet to sit outside! We did see, though, a pair of American black ducks (Anas rubripes) swimming around in a little cove near the dock).

Where were the sea gulls?

Herring gulls have been having a very tough time of it over the past fifty years. The Cornell Laboratory of Ornithology reports that their population has decline 3.5% each year since 1966. That percentage has compounded into an 83% total population decline over this time period! Changes in commercial fishing methods (less dumping of waste fish and refuse), a significant decline in total commercial fishing due to depleted fish populations, and greater control over landside waste disposal, waste dumps and landfills have all reduced the available food for this active, omnivorous scavenger. Further, oil and pesticide pollution and the loss of nesting sites have all had negative impacts on herring gulls. Also, herring gulls incubate their eggs in their huge nesting colonies for over a month, and their nestlings don’t fledge until they are six weeks old! This extended period of egg and nestling existence makes the herring gull quite vulnerable to nest predators (a list that even includes their fellow herring gulls!) and to deliberate human destruction of eggs!

There was an article in The Guardian (June 30, 2010) asking the question, “Why were there no seagulls in Charlottetown. PEI?” One answer came from a reader who reported that a friend of theirs had worked for the Royal Society for the Preservation of Birds (RSPB) back in the 1960’s systematically destroying seagull eggs in nearby PEI colonies (seagulls, according to the RSPB, needed to be destroyed because of their habits of eating the eggs and nestlings of other bird species!).

Harris's hawk (Photo by C. Delgada, Wikimedia Commons)

Harris’s hawk (Photo by C. Delgada, Wikimedia Commons)

Another article I found was published in 2014 on the CBC News web site. This article featured a Harris’s hawk named “Nova” that was hired (along with his handler) by the city of Halifax to patrol the harbor area of the city. The hawk actively killed seagulls and generated a predator presence that greatly reduced the local seagull population!

Deliberate human actions, then, seem to have been one factor in reducing the local presence of seagulls especially in places that wanted outdoor restaurants and harbor-side walkways for tourists (i.e. all of the places that the MS Vandeem took its travelers!).

Another factor that might have been impacting the number of sea gulls that we observed, though, might simply have been the timing of our visit. Both the herring gull and the ring-billed gull were right in the middle of their seasonal nesting periods. Possibly their colonies have been driven far enough away from the high human-use sites of our cruise ship itinerary that the birds were not able to make forays into these towns while still protecting their nests or feeding their nestlings. I like to think that in August the sea gull numbers in this visitation sites would improve. I would be happy to wear a broad-billed hat (and even put a cover over my glass of ale or basket of shellfish) when sitting out at a dockside table if it would mean an accompanying show and clatter of gulls!

 

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Signs of Summer 3: Stink Bugs!

Photo by D. Sillman

Photo by D. Sillman

As we have talked about before, the brown, marmorated stink bug (scientific name: Halyomorpha halys) is a native species of northeast Asia (Japan, Korea, and China) and has become over the past 20 years a serious invasive pest throughout the United States. 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 large populations were being observed throughout eastern Pennsylvania, New Jersey and New York. This insect has now spread to forty states and is especially abundant 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. Its spread to California and Oregon was allegedly via a car driven by a person traveling from Pennsylvania to California in 2005!

The ability of these stink bugs to overwinter is remarkable. There is some mortality among the hibernating bugs, but a significant percentage of them make it through to spring and to their opportunity to mate. A mated female is then able to lay up to three hundred eggs! The relative severity of the winter does, however, affect their percentage of survival. Several models of climate change and global warming have included increased survival of stink bugs at higher and higher latitudinal locations with, then, significantly larger spring and summer populations of this potentially destructive pest. Many of these stink bugs find their way into our houses and spend the winter months hibernating in tiny crevices and hideouts all around us. Their periodic emergence throughout the winter is our only reminder that they are close by!

Brown marmorated stink bugs feed on over one hundred and fifty plant species including a number of crops that are of great economic importance to humans. Fruit trees (especially apple and pear), soybeans, and peanuts are crops significantly damaged by these insects. I have also seen stink bugs in my yard feeding avidly on the grapes growing on my grape vine.

D. Lance Wikimedia Commons

D. Lance Wikimedia Commons

When these stink bugs first made their appearance here in Western Pennsylvania most potential predators were 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 dozens of one liter, plastic bottles with their carcasses! Over the past two years, though, we have not experienced these huge fall and spring outbreaks! This spring I have caught maybe twenty or thirty total stink bugs (I haven’t even filled one plastic bottle yet!). A far cry from the thousands of 2013 and 2014!

Photo by D. Sillman

Photo by D. Sillman

What has happened? It may be that predators are adapting to the noxious scents of the stunk bugs and are reducing their effective populations! We have observed spiders actively trapping and eating them. The picture Deborah took of this jumping spider chewing its way into the captured sink bug is a great visual of arthropod control! Birds (especially titmice and chickadees) regularly flare up to the window screens of my house and snag unwary stink bugs. They fly them over to nearby branches and gobble them down! (Go chickadees!)The predator guilds of our surrounding vertebrate and invertebrate communities have apparently adapted themselves to this new (and formerly incredibly abundant) food source! Control has been achieved, at least in the area immediately around my house!

A few months ago an old friend, Karen Shaver, sent me a link to an article about predators of brown marmorated stink bug eggs. The article (published in the journal Biological Control) was written by Rob Morrison (a research scientist at the USDA-ARS Appalachian Fruit Research Station in Kearneysville, WV). Morrison and his colleagues tested twenty-five potential arthropod predators of stink bug eggs and found several that voraciously devoured the egg masses. Katydids, crickets, ground beetles, jumping spiders and earwigs all actively ate the stink bug eggs (it is especially nice for me to see earwigs talked about in a positive manner! (See my essay about earwigs in my July 23, 2014 Signs of Summer #7 blog!)). Morrison’s group emphasized that modifying habitats to encourage the growth and abundance of these egg predators might be a very effective, long term way to control the populations of this potentially destructive crop pest!

So the brown marmorated stink bug is still with us, but it seems to be getting under control mostly through ecosystem adaptations to its presence and to its potential as prey and food for both vertebrate and invertebrate predators! Pesticides have not been terribly effective in preventing crop damage by stink bugs primarily because of their mobility (they hide in vegetation away from the treated field crops and then swoop in to feed thus limiting their exposure to the applied pesticides). The new observations of active predation of adult bugs and their eggs by an array of arthropod species might indicate that non-targeted destruction of crop dwelling arthropod predators via the pesticide treatments might actually make the stink bug infestation worse!

So, stink bugs are a relatively new and not terribly pleasant sign of summer for Western Pennsylvania. Fortunately, our surrounding biotic community is hard at work to keep them from being the ONLY sign of summer and fall that we notice!

 

 

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Signs of Summer 2: Ticks and Lyme Disease

Photo by D. Sillman

Photo by D. Sillman

Last June I wrote an article about ticks and Lyme disease, too. It has, unfortunately, become one of our important, although depressing, signs of both spring and summer. My dog, Izzy, had a tick last January (during one of the warm spells of our strange winter!) and just got another one a couple of days ago. After a short winter break, the ticks are back!

Pennsylvania is experiencing a population explosion in black-legged ticks (the tick formerly called the “deer tick” but most precisely known as Ixodes scapularis). This tick is small and quite common, and it is found throughout the northeastern and north-central parts of the United States. The reason for its observed increase is not precisely known. Some interesting explanatory hypotheses include the exploding populations of rodents (especially white-footed mice) particularly in our suburban ecosystems.  Fragmentation of forests and the optimal conditions of suburban habitats for these mice along with significant declines in their natural predators have led to great increases in their numbers. Black legged ticks, then, in their larval and nymphal life stages are very likely to find a white-footed mouse on which to feed. These mice are also significant reservoirs for the bacterium that causes Lyme disease, so the ticks that get their blood meal from them have a very high probability of assimilating and then passing on these bacteria.

A second hypothesis that tries to explain the increases in ticks suggests that the observed increase and apparent spread of these ticks involves their return to habitats from which they had been previously extirpated. Tom Simmons of Indiana University of Pennsylvania speculates that Pennsylvania’s forests were once loaded with black legged ticks. Clearing of these forests (95% of Pennsylvania’s forests, as we have talked about previously, were cut sometimes repeatedly since European settlement) and the destruction of the native deer populations (a favorite host of the adult stages of the black legged tick) forced these ticks into greatly restricted habitats from which, as both forest cover and deer populations have recovered, they are now emerging.

Photo by California department of Public Health (Flickr)

Photo by California department of Public Health (Flickr)

Possibly both hypotheses (along with some that haven’t even yet been articulated) are leading to the explosion and spread of both the black legged tick and its symbiotic, Lyme disease causing bacterium (Borrelia burgdoferi). For the last several years, Pennsylvania has led the nation in the number of human cases of Lyme disease (in 2014 there were 7487 conformed human Lyme disease cases in Pennsylvania up from 5904 cases in 2013. I have not been able to find either Pennsylvania or national Lyme disease data for 2015, but I have a feeling that the numbers have increased again!) Further, the Center for Disease Control (CDC) state that the number of reported Lyme cases in the United States (30,000 in 2014) was only 10% of the total number of cases. A lot of people are experiencing Lyme disease!

Let’s go back through the black legged tick’s life cycle:

Eggs deposited in the fall in low, grassy or scrubby vegetation hatch the next summer into the very small, six-legged larva life forms. These tiny ticks typically seek out small hosts (like a white-footed mouse or a bird) but are able opportunistically to attach to larger mammals including humans. These larva, though, are not born with any of the pathogens associated with Ioxdes scapularis and are, thus, unable to transmit any of its diseases (a small piece of good news!). If these larvae feed on a host that is carrying one of  I. scapularis’ bacterial or viral pathogens, though, that tick will become infected with that disease causing agent and will carry it and be able to transmit it throughout the rest of its life cycle.

After the larva has taken its blood meal it molts into the larger, eight-legged nymph life form. This molt often is delayed until the following spring. These nymphs, then, seek a host for their blood meal. These hosts are usually mammals ranging in size from white-footed mice to dogs to cats to deer to humans. Because of the timing of this nymph emergence the spring (May and June here in Western Pennsylvania) is a time of great risk for ticks bites (and disease transmission) for humans!

Photo by D. Sillman

Photo by D. Sillman

After the nymphs have taken their blood meals they molt into adults. These adults are especially abundant in the fall. These much larger ticks (like the one in the picture to the left) typically attach to large mammals like white-tailed deer. The female adult ticks take a large blood meal from their hosts and then use the energy from this feeding to make eggs. The adult male ticks attach to the same hosts, but do not feed (and, therefore, do not transmit pathogens at this stage). They are there to find a female and to mate! The males die shortly after mating and the females die after dropping off of their hosts to lay their eggs in the grassy and scrubby vegetation. Those eggs then overwinter and hatch in the summer to start the life cycle all over again.

The Pennsylvania Department of Environmental Protection collected and tested black-legged ticks and determined that 34% of them carried Borrelia burgdoferi. It is not known if this is an increase from previous years or not, but these data will provide a comparison baseline for future tick assessments.

A few things to remember about ticks and Lyme disease: black-legged ticks are not able to begin blood feeding (and consequential pathogen transfers) until they have been attached to a host for at least 36 hours. Careful examination for ticks and their rapid removal is the best way to prevent contracting the Borrelia bacterium. Preventing tick attachment is an even better strategy to avoid Lyme disease. Also, ticks don’t drop out of trees onto you, they attach to your legs or arms when you brush against vegetation on which the tick is waiting. So, wear long pants and long-sleeved shirts when out in the woods or fields, use DEET-based insect repellents on socks, pant legs, etc. A thorough “tick check” after being out in a potential tick habitat is also a very effective way to reduce the chance of infection.

Careful examination for ticks and their rapid removal is the best way to prevent contracting the Borrelia bacterium. Tick removal is best accomplished using a pair of forceps or a v-slotted, commercial “tick-remover.” Gently pull the tick from its spot of attachment making sure that you remove the feeding structures (the “head”) along with the body. Then dispose of tick in whatever creative way you might wish!

Photo by D. Sillman

Photo by D. Sillman

If you do happen to miss an attached tick you have about a 2% chance of having the Lyme disease bacterium transferred to your blood stream. A few days after a tick bite most people will experience a red bump at the site of the wound. If the tick has transmitted the Lyme bacterium typically (70 to 80%% of the time) the localized redness of the wound will expand over 3 to 10 days into a 5 cm (or more) diameter circular rash. In some individuals the pattern of the redness takes on a “bull’s eye” configuration, but it can just as easily simply be a large red circle. Early Lyme disease can then develop in 1 to 4 weeks in the form of a flu-like illness with fever, fatigue and body aches. If you have been out where you might have encountered a black legged tick and have then observed the red spot expanding into red circle (whether or not the fever syndrome has developed), this is the time to contact your doctor! Antibiotics are extremely effective at this point in preventing the development of most of the serious side effects of Lyme infections!

Untreated Lyme disease can lead to neurological problems, joint pain and a cluster of other, fortunately, uncommon symptoms. “Post-treatment Lyme Disease Syndrome” (PTLSD) (sometimes referred to as “chronic Lyme’s disease) is a very serious but also very preventable condition. Johns Hopkins Medical Center emphasizes that early antibiotic treatment (within 72 hours of a tick bite) with a single 200 mg dose of doxycycline can prevent the development of Lyme disease. If treatment is delayed and Lyme symptoms develop, then longer durations of antibiotic treatment are required. (for more information about Lyme disease I recommend checking out the John Hopkins Lyme Disease Clinical Research Center.

Dogs can also develop Lyme disease. Most dogs (95%) that receive the Borrelia bacterium via a tick bite actually show no symptoms at all. Those dogs that do react to the bacterial infection often develop lameness in one of their legs that typically lasts for a few days. The lameness can then shift to another leg and can be quite debilitating. In some dogs the Lyme infection can also lead to kidney disease and even kidney failure.

The number of dogs who get Lyme disease each year is not known. There is no centralized reporting system to monitor this disease. Anecdotally, I can report that my local vet, a small mostly rural practice, saw well over 100 Lyme disease cases last spring and summer! If every vet is seeing similar numbers, there is truly an epidemic of Lyme affecting our dogs!

Photo by D. Sillman

Photo by D. Sillman

Cats can also be hosts for black legged ticks and have, therefore, the potential to encounter the Lyme bacterium. The Cornell University College of Veterinary Medicine, though, emphatically states that cats are not able to get Lyme disease from tick bites. The bacterium is either not able to be transferred from tick to cat during a blood meal or the transferred bacterium is not able to survive and replicate in the cat.

Welcome to summer, everyone: days of sun and warmth (and mosquitoes and ticks)! We have the very good along with the bad!

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Signs of Summer 1: Spider the Turtle

Photo by D. Sillman

Photo by D. Sillman

My daughter, Marian, got her eastern box turtle from a pet store back in 1998. The store owner said that the turtle (soon to be named “Spider” by my daughter) had been a pet but that the previous owner no longer could take care of him and, so, had brought him to the store so that he could find a home. We didn’t know how old Spider was, but he had all of the features of a mature, adult box turtle (a high domed carapace (upper shell) and a hinged plastron (lower shell) that could tightly close both his head and tail openings. We knew he was a male because of his bright red eyes. Spider easily could have twenty years old (or more) in 1998, and he lived with us for the next eighteen years. When Marian went off to college in 2004, I took over Spider’s care and maintenance.

Spider was an important harbinger of Spring (his early March breaking of his winter-long fast was big news on this ecology blog!) and also of Fall and Winter (his settling into his November torpor in his terrarium foreshadowed the coming cold gray days of winter). He loved to sit in his large water dish often with his head under the water for very long periods of time, and he loved to eat nightcrawlers! He was very adapted to living in a terrarium (he thought food came from the sky and, if hungry, would stretch his neck out and stare straight up (waiting for his earthworms or pieces of fruit to be delivered). I am very sorry to report that Spider passed away yesterday. He never really came out of his winter torpor this year and would not eat (not even very fresh nightcrawlers!). He lasted two months past his usual waking up time but was obviously fading away. Below, in honor of Spider, is the discussion about box turtles from the Virtual Nature Trail.

The eastern box turtle is a familiar and easily recognized inhabitant of the Nature Trail ecosystem. Box turtles are long lived animals that are relatively slow in reproducing. They reach sexual maturity only after four or five (or possibly twenty!) years of life, produce relatively small numbers of eggs, and have a high hatchling mortality rate. Their numbers in the wild have, unfortunately, been steadily declining primarily due to habitat destruction. It is hoped that protected habitats like the Nature Trail and increased awareness by the general public will be sufficient to allow this species to maintain itself as a viable component of our Western Pennsylvanian ecosystems.

Photo by D. Sillman

Photo by D. Sillman

The eastern box turtle is small (4.5 to 6 inches shell width, up to eight inch shell length), land turtle with a high, dome-like upper shell (“carapace”). Younger box turtles can be distinguished by their flatter carapaces. The carapace can have quite a variety of colors and patterns ranging from a smooth, highly camouflaged, green to a brightly marked, brownish black with yellow and orange highlights. The patterns of the markings on the carapaces of box turtles are often distinctive enough to allow identification of specific individuals within a population. The carapace also typically has a ridge (the “keel”) down its centerline and flared edges (the “marginals”).

The head and neck and legs of the eastern box turtle are also heavily patterned with distinctive yellow to orange and, occasionally, reddish streaks. Their under shells (the “plastrons”) range in color from yellow-brown to brownish-black and are hinged to allow movement of the anterior and posterior sections. A box turtle is able to use these hinged plastron lobes to tightly close its head and tail openings. The fit of the closed hinged plastron against the carapace is so tight that not even the blade of a knife can be inserted between them. This ability to tightly encase their bodies within their shells provides the eastern box turtle with a very effective mechanism of defense. Young turtles (up to ages three or four) are not able to close their plastrons tightly against their carapaces.

It is quite easy to determine the sex of an eastern box turtle. Males have concave plastrons, thicker based and longer tails, longer front claws, and bright red or orange eyes. Females have flat or slightly convex plastrons, short, thin tails, and dark red or brown eyes. Also, the “vent” opening (the common, “cloacal” opening of the lower digestive, urinary and reproductive tracts) in the male is typically found past the margin of the carapace while in the female it is located under the carapace edge.

Photo by D. Sillman

Photo by D. Sillman

Eastern box turtles live thirty to forty years in the wild and have been alleged to reach ages of one hundred years or more in captivity.  A box turtle grows very rapidly for the first four or five years of its life reaching sexual maturity in four years but full adult size only by age twenty. Some have stated that only fully grown box turtles, in spite of apparent earlier sexual maturity, are actually reproductively active.

Eastern box turtles are found from New Hampshire to Georgia, and west to Michigan, Illinois and Tennessee. They prefer open woodlands, pastures, and marshy meadows. They are most likely to be found in moist habitats and spend a great deal of their time buried in the leaves and surface soils and hidden in the brushy piles of their forest habitats. Their optimal environmental temperatures are between 70 and 85 degrees F, but they will tolerate nighttime temperatures down into the 50’s. During the summer, they are seldom active during the mid-day heat and do most of their hunting and foraging during the cool, early morning hours. They often soak themselves in puddles, seeps, springs and other muddy places for hours or days at a time. As temperatures fall in the autumn, eastern box turtles enter into hibernation (usually starting in October or November) and burrow into loose soil, mud, or abandoned mammal burrows. As the soil temperatures drop with the coming winter season, the turtles burrow deeper and deeper into their hibernacula.

Eastern box turtles are predominantly carnivorous during their younger years and become more and more herbivorous as they age. Prey items taken by box turtles include, snails, worms, insects, spiders, frogs, snakes lizards, small mammals, and carrion. They also eat fruits, berries, leaves and many types of mushrooms. Some of the mushrooms consumed by box turtles are very toxic for humans, so it is inferred that the turtles are unaffected by these potential poisons. Humans eating box turtles that have recently fed on poisonous mushrooms may become quite ill due the toxins that have accumulated in the turtles’ flesh.

Photo by D. Sillman

Photo by D. Sillman

Turtles will forage over an area the equivalent of two football fields over their lives. Adult individuals occupy “home ranges” of variable sizes (larger in less favorable habitats or in systems with relatively low population densities, smaller in more favorable or more densely populated habitats). Immature individuals (less than nine years of age) and many mature, but un-established males move extensively about as “transients.” The directionality of their movements is, apparently, “one way,” and quite energetically directional! (So, if you rescue a box turtle crossing a road ALWAYS put it over on the side to which it was heading!).

Box turtles are often found near to each other and can form range-overlapping, socially tolerant groups of three or four individuals. Fighting and other types of aggressive behavior are rare with the exception of occasional “sparring” matches (especially between completing males) that involve alternative bouts of two individuals biting each other’s shells with, obviously, little damage to either individual. Eastern box turtles walk with a steady, energetic stride holding their heads upright. They can travel 50 yards or more in a single day and strong homing instincts that compel them to move in the direction of their home ranges.   

Photo by D. Sillman

Photo by D. Sillman

Female box turtles are callable of storing sperm in their oviducts for up to four years and are thus able to produce viable eggs for many years following a single mating. They will mate between May and October. Eggs are laid into flask-shaped holes that are three to four inches deep. The holes are meticulously dug by the female into the soil of sunny, warm sites. Three to six elliptical, leathery eggs are laid and then covered to incubate and then hatch on their own. Several clutches can be laid per year. Incubation lasts two to three months. A clutch that hatches late in the season may over-winter in the nest hole and emerge the following spring.  

This will be my first summer in eighteen years without a turtle to play with and watch and feed. Spider will be missed!

 

 

 

 

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Signs of Spring 13: Mosquitoes!

D. Sillman

Photo by D. Sillman

As the temperatures start to slowly rise back up into more comfortable ranges, and Signs of Spring give way to Signs of Summer, Deborah’s and my thoughts inevitably turn to pulling out our folding chairs and getting outside in the evening to watch and feel the day come to a close. We usually get most of the month of April and then a good part of May (depending how fast summer really sets in) to enjoy long evenings outside, but by June something comes up that limits our time outside: mosquitoes.

There are always a few mosquitoes right away in the spring, but it takes some time and some continuous warm temperatures for the real swarms to arise. This staged invasion is due to the way that different mosquito species survive the winter.  Our native mosquito species, by the way, don’t seem to be negatively affected by very cold winters or excessively stimulated by very mild winters. They are able to roll with our fluctuating climate and pull themselves back into their reproductive (and blood meal requiring) life stages with great ease and efficiency.

Photo by J. Gathany, CDC Wikimedia Commons

Photo by J. Gathany, CDC Wikimedia Commons

Some of our mosquitoes overwinter as cold resistant eggs while others hibernate as larvae. There are also a few mosquito species that overwinter as mated adult females. These adult females emerge early in the spring and are ready right away for a blood meal so that they can finish making their eggs. They are the first attacking wave in the early spring. Again, cold spring temperatures may delay their emergence, but the cold does not seem to significantly reduce their numbers. So there are a few mosquitoes active as soon as air temperatures get sufficiently warm, but the swarms don’t come until all of those overwintering eggs and larvae mature and begin to seek their blood meals.

There are so many things to say about mosquitoes, and so many different points of view to take about them!

Photo by Abhishek, Wikimedia Commons

Photo by Abhishek, Wikimedia Commons

Dr. Nora Besansky is a biologist at Notre Dame University who specializes in mosquitoes. She was interviewed on NPR back in February and spent most of her on-air time emphasizing how beneficial and important most mosquitoes are. Of the four thousand or so species of mosquitoes less than one hundred actually transmit human diseases. The rest occupy important places in many food chains (for mammals, birds, fish, amphibians, reptiles, and wide range of insects and other arthropods) and also function as pollinators for many species of plants (all adult mosquitoes, Dr. Besansky emphasized, drink flower nectar). Blood feeding by mosquitoes is only carried out by females and is needed to provide the protein and iron required to make viable eggs. The female mosquitoes can take a blood meal from a wide variety of potential hosts. The list of possible hosts, in fact, is nearly identical to the list of what can eat mosquitoes, and different mosquito species specialize on particular types of hosts.

Another perfectly reasonable point of view, though, concerning mosquitoes looks at the nearly one hundred mosquito species that can transmit diseases to and in between people. There are some serious diseases on the mosquito transmitted list! Malaria, yellow fever, Dengue fever, West Nile virus, and a whole slew of encephalitis syndromes are all carried by mosquitoes.  Over the past winter, our awareness of a new mosquito borne virus spreading across South and Central America, the Zika virus, has triggered intense discussions about mosquito control procedure and the safety of travel to Zika affected areas. Each year, according to EB Medicine (an on-line medical reference site), seven hundred million people get a mosquito transmitted illness. Most of these cases occur in human populations residing in tropical and subtropical climate zones, and about half of all of these cases involve malaria.

So here in Western Pennsylvania (which for now anyway, is about as non-tropical or subtropical as you can get!), we have nothing to worry about, right? (I bet everyone reading this can feel the coming bad news that is about to extend this essay!).

Anopheles (Photo by J. Gathany CDC Wikimedia Commons

Anopheles (Photo by J. Gathany CDC Wikimedia Commons

Let’s talk about the mosquitoes that spread some of these diseases: Malaria is caused by a protozoan parasite called Plasmodium. Plasmodium is most commonly spread by mosquitoes of the genus Anopheles. The very good news is that Anopheles mosquitoes, unlike our more robust native mosquito species, cannot survive our long, cold winters and are, therefore, not found in Western Pennsylvania. Fortunately, malaria is not something we have to worry about locally!

Aedes aegypti Photo by J. Gathany CDC Wikimedia Commons

Aedes aegypti Photo by J. Gathany CDC Wikimedia Commons

When we talk about mosquito spread viral diseases, though, like yellow fever, Dengue fever, and Zika, we are especially (but not exclusively) talking about mosquito species that are in the genus Aedes. Aedes aegypti , in particular, is an active, wide-spread tropical and sub-tropical mosquito species and is often the species involved in the transmission of these illnesses to humans. Aedes aegypti has all sorts of specializations that make it very difficult to control. It can lay its eggs in very small pools and puddles of water. Its larvae can develop successfully in the tiniest volume of even the most stagnant water (think rain water collected in a discarded tin can or old tire!), and bacterial growth in these water sources actually stimulates egg development! The adult Aedes mosquitoes are most active at dusk and at dawn especially in shady areas, but they can bite (and spread their viruses) at almost anytime during the day and also at any time of the year. Adults can also live exclusively inside of houses and other buildings often taking their blood meals while the people in these buildings are asleep.

Aedes albopictus Photo by J. Gathany CDC Wikimedia Commons

Aedes albopictus Photo by J. Gathany CDC Wikimedia Commons

So where is the boundary between the temperate and subtropical climate zones? How about 250 miles from here? How about even closer than that? There are established populations of Aedes aegypti  and other Aedes species in Washington, D. C.! There are also periodically occurring populations of Aedes albopictus (the “Asian tiger mosquito”) right here in Western Pennsylvania, and there is some indication that the Asian tiger mosquito is developing a tolerance for our cold winters and may be setting itself up as an established alien species! The Asian tiger mosquito can carry all of those diseases listed above and may represent a significant human health threat!

It is always “good news/bad news” when thinking about these ecological and medical problems. The really good news is that our cold winters limit the ability of these virus and parasite carrying mosquitoes to establish themselves in Western Pennsylvania. The bad news is that these mosquitoes are evolving to get around that limitation and, with the ongoing warming associated with climate change, the climate seems to be meeting the species changes half way! Mosquitoes and ticks, unfortunately, are some of our signs of spring and summer! I will talk about ticks next week in our first “Signs of Summer!”

 

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Signs of Spring 12: Getting Lost in the Woods

Photo by D. Sillman

Photo by D. Sillman

Last Monday Deborah and I took advantage of an open day in our Penn State schedules and headed up to Todd Nature Reserve. The Nature Reserve (formerly called “Todd Sanctuary”) is a rocky, stream crossed, 176 acre site owned and maintained by the Audubon Society of Western Pennsylvania. It is in Sarver in southeastern Butler County and has been, for all of the thirty-three years Deborah and I have lived in this area, one of our favorite places to hike. There are five miles of crisscrossing hiking trails in the reserve. A two mile “Loop Trail” encircles the site’s perimeter and takes you from stream beds to ridge tops and back again through young to middle-aged hemlock stands and a variety of mixed hardwood forests. Shorter trails (with evocative names like “Hemlock,” “Indian Pipe,” “Pond,” “Warbler,” and “Polypody”) interconnect fern capped rock cities with densely vegetated copses with the human constructed pond (built in 1969).

There were no other cars in the gravel parking lot, so we knew that we would have the reserve to ourselves.   Our plan was to do the Loop Trail and keep our eyes open for both birds and wildflowers.

We walked up to the cabin and picked up a new copy of the trail map and then crossed the poison ivy rich clearing to enter the dark, cool hemlock forest. The red blazes of the Loop Trail took us to the right, and we walked up and over some rolling terrain in the deep cover of the hemlocks taking care to watch each footfall on the very irregular, rocky surface.

There are few decisions to be made while walking these trails. The paths are well worn and the blazes are always clear. Occasionally you need to jog around a fallen tree or bypass a muddy low spot, but it is not really possible to get lost.

Which is a shame (and it is also, to quote Anton Chekhov, the proverbial “gun hung on the wall” in Act 1!).

The times that Deborah and I have been lost on hikes, while not too very numerous, are times that are very vividly etched in my memory! There is some type of primal reaction, an instinctive intensity that rushes over you when you realized that you are out in the middle of an unknown area with no clear idea of where home (or your car) or help of any kind might be!

Mt. Marcy Photo by D. Tripp, Wikimedia Commons

Mt. Marcy Photo by D. Tripp, Wikimedia Commons

I remember being lost up in the Adirondacks while on a backpacking trip with our grad school friends, Mark and Terre. We were hiking up around Mt. Marcy and were enjoying a beautiful, sunny, early May day after post-holing our way across the lingering snow fields higher up on the mountain. Walking was easy and talking was even easier. All of sudden we realized that we were on a trail that had no blazes. We consulted our maps and could not make any sense of the terrain around us and the topographic detail of the map! We also realized that we didn’t have a compass and so were guessing at directions. There was nothing to do but follow the trail back.

We hiked a good mile or two back along the trail getting more and more anxious about where we were and where we were going to end up. Finally, we found a turn blaze that we had missed and were back on our trail and back on our map.

The feeling you get when you re-find your trail, when you see your blazes again is incomparably wonderful! Almost worth the anxiety that led up to it!

When Deborah and I hiked the Baker Trail a few years ago we also lost the trail a couple of times. One time we were able to use our maps and compass (I always carry a compass now!) to bushwhack across a field and forest stand to regain the trail. Another time we ended up wandering around on an active strip mine for several hours (because the trail blazes we were trying to find only faced one direction! They could not be seen when approaching the trail from an off-trail location!). Another time, we crossed a trail section that was being redesigned and the familiar yellow, Baker Trail blazes had not yet been placed (we wandered around for quite a while until, with great joy, we found a rectangle of bright yellow paint on an old black cherry tree!).

Anyway, you can’t get lost on the Todd Nature Reserve Trails (or so I thought!).

Photo by D. Sillman

Photo by D. Sillman

Along the Loop Trail there were abundant wildflowers. The broad, flat, parasol-like leaves of Mayapple (Podophyllum peltatum) spread out alongside the trail. Most of the plants had not yet opened their white flowers. Compared to previous years, the Mayapple seems to be developing a week or two later this year!  Trillium (both the large flowered white and the red) are still in bloom here, too. On most of the trails closer to our house the trillium flowers have faded and fallen. The “season-time” here is a week or two behind our local ecosystems.

Multiflora rose is growing in scattered patches that are getting larger every year. Garlic mustard is also becoming increasingly abundant. These two invasive species have the potential to do a great deal of harm to the native plant species in the Reserve. As I talked about last year, the impact of the garlic mustard extends to its stresses it exerts on the soil fungi that many plants (like Mayapple) require to flourish.

Photo by D. Sillman

Photo by D. Sillman

There is a very nice array of native plants in flower: mitrewort, dwarf ginseng, clintonia, jack-in-the-pulpit (pictured to the left), Solomon’s seal, wild geranium and many more (Deborah listed twenty flowering species in her notes!). Ferns are also abundant along the trail including Christmas fern, evergreen woodfern, New York fern, sensitive fern, interrupted fern, hayscented fern, cinnamon fern, and rattlesnake fern (one of Deborah’s favorites). There is also an abundance of raspberry and blackberry canes growing along the trail.

We also met up with a very belligerent eastern garter snake (Thamnophis sirtalis sirtalis) on the now seldom used trail that goes to Inspiration Point (a formerly cleared spot the overlooked the deep ravine cut by Watson Run). The snake, who tried very hard to

Photo by D. Sillman

Photo by D. Sillman

convince us of his ferociousness by coiling up into a tight ball and lunging at us with an open mouth, seemed very put out that we didn’t immediately flee. We walked past him and went on to the point. He was slithering away when we walked back past a few minutes later!

As we approached the end of the Loop Trail and were getting close to the Cabin and the walk back up to the parking area, we saw a set of signs marking a newly completed trail called the Shoop Trail. This trail was not on our map, but the sign described it as a 0.9 mile loop, so we decided to give it a try.

The first part of the Shoop Trail was through a young hardwood forest. The path was firm and dry and the wildflowers abundant. The second part of the trail dipped down a bit into a spring fed swale and the trail became muddy and ponded over and very difficult to walk on. The trail then opened out into an old field full of young spring weeds and a scattering of the same invasive tree/shrub that we see regularly in Harrison Hills: privet. We followed the edge of the field toward the east and re-entered the woods on a broad, grass covered path.

About 50 yards down the path we heard and then saw a little warbler flitting around in the dense branches of the surrounding trees and shrubs. It took quite a while to get a clear look at him, but we identified him as a blue-winged warbler (Vermivora pinus)! Also, just before this warbler had flown into view, Deborah had spotted a plant that she had never seen before (its identity is to be determined!). We agreed that the extra walk on the Shoop Trail, mud and sloppy trail surfaces and all, had been more than worth it.

Then we realized that there were no trail blazes anywhere to be seen!

We backtracked to the spot where the incoming trail had opened out into the field and then carefully walked the edge of the field looking for more blazes to indicate the direction of the return loop. We could not find any.

Now, this is as “lost” as you can get in the Todd Nature Reserve. We knew which direction the cabin and foci of the trail grid was, but we just didn’t want to slog our way over the muddy sections of the Shoop Trail that we had already walked! We could see a road about a quarter of a mile to the west and assumed (correctly as it turned out) that it was the road that ran past the entrance to the Reserve. So we cut across the field, walked over a culvert that spanned the creek (which was high and running fast from all of the recent rains), and took the half mile or so walk back to the parking area.

There was very little adrenaline of rush in this “being lost” adventure, but we did get a nice extension on our walk around Todd!

Happy Spring (and almost Summer)!

 

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Signs of Spring #11: Field Sparrows and Bluebirds

Photo by D. Sillman

Photo by D. Sillman

Deborah and I were up at Harrison Hills Park two weeks ago hiking the route between our assigned bluebird boxes and keeping our eyes open for wildflowers and interesting birds. We parked near the cluster of purple martin houses (no martins yet!) just across from the Environmental Learning Center and were immediately greeted by a long, trilling, melodic song coming from the top of one of the many privet bushes/trees that are strewn across the meadow.

I had my larger (and heavier!) binoculars in the trunk of the car (I carry my smaller ones with me when I hike), so I got them out and zoomed in on the privet bush. Our singer was a male field sparrow (Spizella pusilla) (pictured above) singing so hard and loud that his little body shook with the effort!

The field sparrow is one that I never see around my house. They are a true “field” species that is intolerant of human activity and the structure (and hustle and bustle) of urban and suburban habitats. They are year-round residents of our area, but really show themselves off in the few weeks prior to mate selection and nest establishment.

Photo by D. Sillman

Photo by D. Sillman

In the winter, male and female field sparrows join multi-species flocks that included a mix of other sparrow species (including song sparrows and white throated sparrows). Field sparrows are much less aggressive than these other two types of sparrows and, so, probably spend much of their winter dominated by these more energetic birds. The field sparrow’s response to continually being displaced from overwintering food sources (primarily grass seeds) is frequently to return to sites following predator disturbance more rapidly than its flock mates. The increased risk of a lingering or returning predator is more than offset by a chance at a decent feed!

Male field sparrows break away from these winter flocks in early spring and return to their specific breeding sites with great reliability. In these sites, the males begin to sing to mark their territories and interact with each other to establish their breeding boundaries. Females arrive later, and they tend not to return to the territories of their birth nests or even to the territories in which they might have bred in the previous year. This more random selection of breeding sites by females (couple with the great specificity of site selection by males) very effectively reduces inbreeding within this species.

Females are frequently greeted by the male with physical contact and superficially aggressive behaviors (the male may fly at a female entering his territory and actually knock her to the ground! Maybe there is some pent energy from being so passive and submissive all winter?). Mate selection, though, quickly follows these altercations, and the female (with little help but often with much attention by the male) builds the nest.

Field sparrows can have more than one breeding cycle in a season, and their nest locations are quite different in the spring vs. the summer. In the spring the nests are usually built on the ground amid the growing grasses and weeds. Tree or shrub locations are still not adequately leafed out to provide cover or concealment. Later in the summer, though, the nests are built in the fully leafed out trees and shrubs where they are more protected against nest predators.

In the spring and summer field sparrows take advantage of a wide range of available foods in addition to their nearly continuous diet of seeds. Insects (including flies, bees, beetles, grasshoppers, and caterpillars) and spiders are protein and energy rich food sources consumed by the adult field sparrows and fed almost exclusively to their nestlings.

Field sparrow numbers have declined in recent years primarily due to habitat loss. They are a very welcome member of the Harrison Hills Park avian community, though.

Photo by D. Sillman

Photo by D. Sillman

This is our second year monitoring the twenty-eight bluebird boxes scattered across Harrison Hills Park. The original placement of the boxes was based more on convenience of access than on bluebird ecology, and one of last year’s goals of our “Cavity Nesting Team” (the name of our eight membered volunteer group) was to explore the possible variables that influence the selection of nesting boxes by bluebirds and also tree swallows (another important “cavity nester”).

We found that, in general, successful bluebird boxes were located about 30 to 40 feet from the edges of the woods (definitely not right on the edge of a field and definitely not in the center of a field). Most bluebird occupied boxes faced south (or southeast), and that bluebirds did not occupy boxes close to other bluebirds. Two bluebird boxes were very close to (within 100 feet) occupied swallow boxes, though. Bluebirds reproduce in staggered waves (three reproductive time events (April/May, May/June, July/August). Not a rigidly timed event). Survival to fledgling in our boxes was 66% overall. Early clutches had a higher survival to fledging (77%) than later clutches (50%).

Successful tree swallow boxes, on the other hand, were located further from the edges of the woods than the successful bluebird nests and were much more in the centers of the meadows. Two swallow nests were located near the Park’s big pond. Two swallow nests were located within 100 feet of active bluebird nests, and tree swallows reproduce in a more rigid time frame. Almost all nesting occurred in a May/June time frame (only one nesting cycle).  Survival of egg to fledgling was 71% in our boxes.

Last Fall the Cavity Nesting Team initiated a plan to put some of our observations and hypotheses into practice. We left all boxes that had tree swallow or bluebird nests in them where they were, and we moved the “no nest” boxes according to the following criteria:

  1. To the centers of the fields (to favor swallows)
  2. Near the ponds (to favor swallows)
  3. To 10 to 20m from the field edges, at least 100m apart, near mowed areas if possible, and put them out in pairs (to increase visibility and influence the birds’ perceptions of habitat quality)(to favor bluebirds)
  4. And we tried to orient all boxes to face the south or southeast

In October 201 we moved seven of the nine non-nested boxes into locations that corresponded to these hypothesized “more favorable” locations. We are now watching our boxes!

On our hike around two weeks ago Deborah and spotted our first bluebird eggs! We also opened one of our boxes and found a female bluebird protectively incubating (and maybe laying) eggs! Several of the other boxes have starts of nests, eggs and active bluebird “look outs,” too. Lots of bluebird action at Harrison Hills! I will keep you posted!

 

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Signs of Spring 10: Vernal Pools (and more!)

H. crucifer Photo by USGS (Public Domain)

H. crucifer Photo by USGS (Public Domain)

Spring frogs are important harbingers of the season in Western Pennsylvania, and Deborah and I listen for them carefully. The Spring Peepers (Hyla crucifer) are usually the first frogs to make their presence known. They begin their soft, peeping group choruses in and around small ponds and wetlands as soon as there are some warm, spring evenings. This year, however, we didn’t hear any peepers out in the usual places around our home.  This past winter’s lack of snow fall (leading to a low level of spring snow melt) and our very dry March and April may have cut into available water habitats for these little frogs to use as mating sites.

Gray tree frogs (Hyla versicolor) typically start their resonating trills soon after the peepers. This year we did hear some tree frogs out around our house in spite of absence of peepers, but their numbers and volumes were greatly reduced from previous years.  In some years the tree frogs continue to trill well into the summer. We’ll see if they can re-group or gather new strength.

There is a third frog that we regularly look for in this winter-to-spring transition: the wood frog (Rana sylvatica). We have to drive some distance, though, in order to see and hear wood frogs because they don’t do well in areas that have too many people.  They need dense, quiet woodlands with lots of leaves to hide under and lots of low spots for their spring mating pools!

Photo by D. Sillman

Photo by D. Sillman

So, Deborah and I drove down to Ohiopyle last weekend and met up with Rob and Michele for our annual, spring hike around Ferncliff Peninsula. We were looking for any new (or different) signs of spring, but in particular we wanted to see if we could find the wood frogs that were so abundant here three years ago (on a warm afternoon hike in late March 2013). The timing of the emergence of the wood frogs from hibernation and their frenetic mating in the temporary, spring (or “vernal”) pools of water (accompanied not by trilling or peeping but by a call that sounds like the quacking of a duck!) are all influenced by air temperatures and the abundance of surface water. Because of our very non-typical winter and spring, we were curious if there would be any amphibians at all! Also, incompletely filled pools might dry out before the aquatic larvae of the breeding amphibians have had sufficient time to develop legs and lungs. This disastrous outcome could wipe out an entire year’s crop of young amphibians.

Photo by D. Sillman

Photo by D. Sillman

We walked out onto the Ferncliff Peninsula at Ohiopyle. The day was getting warm, and it felt good when the sun finally 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 at the Ohiopyle Falls. There was quite a bit of new flood debris along the shore, but Rob commented that the water level seemed lower than usual and the river rocks seemed more exposed and extensive than in previous years. Possibly in response to our near-drought more water is being held back behind the Youghiogheny Dam.

The isolated pools up and around the shoreline rocks, though, were full of life. Hundreds of tiny, black tadpoles were clustered together in the sunlit sections of the pool. Water striders were whirling and skimming across the still water and were actively bouncing into each other (establishing territories or mating?) and searching for food.  There were several types of eggs in the pool including the very distinctive cloudy and opaque eggs masses of the spotted salamander. Rob saw a small, brown salamander hiding in the brown leaves at the bottom of one of the pools. He poked it with the tip of his hiking stick (very gently!) and it swam to the back of the pool and buried itself in the leaves.

Photo by D. Sillman

Red Trillium Photo by D. Sillman

 

The trail climbed up away from the rocks and headed out along one side of the peninsula. The red maples and yellow poplars were all just starting to leaf out. They were covered with light green halos of tiny leaves. The abundant hemlocks and the scattered white pines made dark, bordering lines of green around the spindly hardwoods, and thick bunches of rhododendron bushes added their waxy deep greens to the landscape. The greens stood out sharply against the overwhelming brown ground cover of scattered, dead leaves. We also saw some spring wildflowers: red trillium, sessile leafed bellwort, and star chickweed (all pictured above and below).

 

Sessile leafed bellwort Photo by D. Sillman

Sessile leafed bellwort Photo by D. Sillman

Every time we hike this trail something happens to separate Deborah and Michele (who inevitably walk out ahead at a rapid pace) from Rob and I (who lumber along at our slow (but steady!) pace). When we made the big turn in the trail after inching along a narrow rock side trail that ran along a steep drop to the river, we got a glimpse of two people walking up and over a trail that ran up to the top of the peninsula. We thought that Michele and Deborah had taken the turn to go up, so we did too. Unfortunately we realized (after fifteen minutes or so of scrambling up the rocky trail) that the people we were following were not Michele and Deborah. We hope that they didn’t notice that we were stalking them!

We cut back down to the lower Ferncliff Trail, but by then were hopelessly separated from Deborah and Michele. Rob’s cell phone died in mid-text “where are…?” and so we plodded on following a couple and

Star chickweed Photo by D. Sillman

Star chickweed Photo by D. Sillman

their three little girls trying not to fall too far behind them!  Rob and I continued on the Ferncliff Trail and eventually re-made contact with Deborah and Michele near the trail’s end parking lot.

The Ferncliff Trail connects to the Great Allegheny Passage Trail. This is where we had seen the series of vernal pools full of wood frogs back in 2013. We checked them out very hopefully but were very disappointed by the water levels and quality. The pools were about half of their widths and depths of three years ago and were choked with algae and sediment and bits of litter and tossed debris. We saw neither frogs nor any egg masses nor any tadpoles. I don’t think that it will be a good year for amphibians in Western Pennsylvania!

Vernal pools are an important part of the forest habitats throughout the Eastern United States. They are small, shallow bodies of water with fluctuating water levels. Typically, these pools attain their maximum depths and volumes in the spring and their minimum depths and volumes in the summer. Many of these pools completely dry up especially in drought years or years of meager snow fall (like 2016!). A vernal pool must, according to Elizabeth Colburn in her excellent book Vernal Pools: Natural History and Conservation (2014), stay flooded for two or three continuous months, so it is, indeed, something more than just a rain puddle.

Vernal pools have no continuous inflows or outflows. They exist as isolated basins in the midst of their woodland ecosystems. This disconnection to streams and the possibility (or, more appropriately, the probability) of drying out generates a critical ecological feature of these pools: they do not have fish. And, this distinctive absence generates an aquatic habitat especially conducive to the development of a wide variety of amphibians whose eggs and immature life stages are heavily preyed upon by many fish species.

Vernal pools are greatly affected by the types and densities of the trees that surround them.  The chemical nature of the prevailing leaf species influences the acidity, turbidity and nutrient levels of the pool waters.  The history of a pool and the regularity and predictability of its occurrence and duration also has profound influences on the diversity and abundance of its breeding amphibians.

These pools in the Ohiopyle forests have been in place for many years and rely on sufficient melt and spring rain to fill them sufficiently. Let’s hope that next winter is a bit more snowy and that the March and April rains are more abundant. We need to hear ALL of the spring frogs next year!

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Signs of Spring 9: Red Maples (part 2)

Photo by D. Sillman

Photo by D. Sillman

I am looking out across a broad river valley here in Western Pennsylvania. At least one third of the trees I see are red maples (the photo to the left was taken about a month after the photo in last week’s blog). Last week I wrote about the amazing reproductive potential of the red maple and the readiness of its seeds to germinate and survive as seedlings in almost any natural and human generated habitat. Now let’s talk about the ultimate forest sculpting force in Pennsylvania today: the white-tailed deer.

Red maple seedlings are extensively browsed by deer in the winter. So, there is a large advantage for a seedling to grow as fast as possible in order to stretch itself above the browse level. Growth rates of red maples are prodigious: one foot height increases in the first year, two feet per year after that. Red maples, though, are also able to sprout after the above ground stem has been damaged. After a seedling has been browsed by a deer, for example, that individual can actually re-sprout at a growth rate of three feet per year! Sprouts, initially, have a faster growth rate than seedlings! There may actually be a selective advantage for a seedling to be browsed so that this accelerated growth spurt can be achieved!

Photo by D. Sillman

Photo by D. Sillman

The symbiosis between deer and red maples, then, is complex and, on the surface, seemingly contradictory. Deer eat red maples voraciously in the winter. But this winter browsing may actually stimulate those red maple individuals that are capable of the most robust sprouting response, to attain dominance in their ecosystem! Further, the sheer numbers of red maple seedlings in a forest floor community make it likely, especially in years of abundant browse, that at least some of the red maple seedlings will be passed over by the deer and, thus be able to survive to grow. Tree species that generate smaller numbers of seedlings are less likely to survive this intense survival filter of deer browsing.

Many insects feed on red maples, but few of these insects are serious, lethal pests. Gypsy moth larvae, for example, feed preferentially on oak leaves over red maple leaves possibly because of certain alkaloid chemicals that are present in the red maple leaf tissues. These alkaloids may also be an important in the red maple’s resistance against excessive summer leaf browsing by deer.

Public Domain

Public Domain

Red maples are extremely sensitive to fire. All of its life stages (seedling, sapling, “pole” tree, and mature tree) are easily damaged and killed by forest fires. Fire is a very effective way by which a forested ecosystem can be scoured clean of red maples! The minimal presence of red maples in pre-settlement forests and their predominant confinement to very wet habitats may be explained by the regular occurrence of fires in the drier habitats. Some of these fires, in fact, are thought to have been set by Native Americans in a management strategy that increased the dominance of oaks and sculpted the physical structure of the forest itself into a configuration more conducive to hunting and the support of deer populations. The wide-spread suppression of forest fires throughout the twentieth century may be an extremely significant factor in understanding the expanding distribution and abundance of red maples.

The pre-settlement forests of Pennsylvania were dominated by oaks (especially white oak), American chestnut, eastern hemlocks, and white pines. All of these tree species were extensively cut for timber, mine props, railroad ties, firewood, charcoal, tannins and other wood chemicals, and paper pulp. The oaks in the re-growing, secondary forests were then exposed to intense browse pressures by the re-surging white-tailed deer populations, and defoliated often fatally by the explosive outbreaks of the introduced gypsy moths. The suppression of forest fires also removed an on-going environmental factor that favored the dynamic persistence of the oak forest. The American chestnut was functionally exterminated as a potential canopy tree by the twentieth century expansion of the introduced fungus that caused chestnut blight. Eastern hemlocks were logged into near extinction in the state and, most significantly, the moist, highly shaded forest floor microhabitat in which their extremely specialized seeds and seedlings could germinate and grow was destroyed by the clear cutting and subsequent soil and litter erosion and drying exposure to direct sunlight. White pines thrived on sites with coarse, well drained soils and relied on periodic fires to reset their successional sequences and maintain a site consistency of white pines. Fire suppression, then, also limited the ability of white pines to reestablish their “pineries.”

Photo by D. Sillman

Photo by D. Sillman

The pre-settlement forests, then, were densely populated with highly specialized trees that had established and maintained themselves in their habitats. These tree species modified the characteristics of their habitats to favor their growth and survival. These species were also adapted to respond to the catastrophic but regularly occurring disturbance events that beset their ecosystems. Settlement, then, changed everything. The suppression of fire, the destruction of the ancient, persisting seed beds of the forest floor, and the introduction of exotic insects and diseases altered the stress and selection matrix of these forests possibly forever.  Tree species with broader tolerance ranges especially with regard to reproductive processes and stages were now favored. And, the red maple is acknowledged to be the “ultimate generalist.”

So, the question I have been pondering here in the shade of this wonderful red maple in the company of generation after generation of red maples, is “why are they here?” and “why are they everywhere I look?”

The destruction of the pre-settlement forest opened many niches. The failure of the hemlocks and white pines to reproduce, the loss of the American chestnut, and the on-going failure of the oak forest to re-establish itself reduced competition, and the incredibly fecund and adaptable red maple swept into the available ecological spaces.

Will other tree species succeed the red maple? Will northern red oaks, sugar maples, or American beeches (all slow growing but very shade tolerant species) become established in the understories of the red maples and eventually grow into the canopy? Or will the red maples maintain their dominance via their staggering numbers and ecological tenacity? Check back in hundred years or so to see!

 

 

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Signs of Spring 8: Red Maples (part 1)

Photo by D. Sillman

Photo by D. Sillman

There is a trail that Deborah and I have hiked many times over the years. We call it the “Up and Over,” and it runs up the north side ridge of the Kiski River and then down into the ravine of Roaring Run Creek. It is a very seldom walked trail although there are a few mountain biking paths that get some activity especially on nice, sunny weekend days. A great thing about hiking familiar trails is that you have a mental map of all of the nice spots where you can take short rests along the way. One of these places on the Up and Over is a sitting log under a large red maple way up on the crest of the Kiski Ridge. When you sit on the log (munching some favorite snack and having a cool drink from your water bottle) you look down over the Kiskiminetas River which runs fast and shallow over its red-brown, silt covered rocks and out across the tree covered framing hillsides and the distant ridges. Deborah’s picture above shows the scene from this spot in early April (next week I’ll show you what it looks like a month later!).

I remember sitting in this spot a couple of years ago in the third week of March before any of the trees had leafed out. It was a sunny day but damp and cold. There were even a few lingering patches of snow on the north-facing slopes and in some of the more shaded hollows.

Red Maple flower Public Domain

Red Maple flower Public Domain

About a third of the trees had a fuzzy, reddish glow around their sun-lit branches. These were the first flowering trees of the season and quite obviously from this high vantage point the single most abundant type of tree throughout this river valley. These gently glowing, red flowering trees were red maples.

The other common names of red maple describe important aspects of its ecology and uses. “Swamp maple” and “water maple” tell us that this species is a tree of wet soils. “Soft maple” indicates that the wood is easily worked (and maybe not as strong as the wood of some other types of trees), and “scarlet maple” is a name for those who maybe crave more elegant adjectives!    The presence of red maple all along the river and up the creek-cut hollows made sense relative to the tree’s ecological names, but the abundance of the tree along both the north-facing and south-facing ridges doesn’t seem to fit. Red maples were everywhere. Why?

Through the twentieth century, the red maple became one of the most widespread and abundant trees in eastern North America. In the pre-settlement forest, red maple was found in the places described by its many common names. It was a relatively minor tree of the overall forest and was concentrated in wet, poorly drained sites. How and why did this species proliferate so greatly? How and why did it spread over most of the available landscape?

Looking around from my sitting log I see red maples of all sizes and ages. Thousands of tiny seedlings fill up the spaces around the larger trees, hundreds of its thin saplings rise several feet up above them, and dozens of its skinny “pole” trees in turn rise up over them. This is a red maple forest in a robust state of reproduction. Again the question, “why red maple?”

One of the reasons that explain the “why and how” of red maples is the tree’s great ability to make seed. Flowering and seed production can begin in a red maple as young as four years of age. Young trees that are two to eight inches in diameter can make tens of thousands of seeds each year. Older trees that are a foot or more in diameter can make a million seeds in a single year. Bumper crops of seeds are produced every other year, but every year is a good seed year for red maples.

Photo by Dcrjsr, Wikimedia Commons

Photo by Dcrjsr, Wikimedia Commons

The seeds mature in double, winged samara and are shed from the parental tree in late spring. There are very few germination requirements for the red maple seeds. They can germinate in the shade under the parental tree, or in the direct sun many hundreds of yards away. They can germinate in very wet conditions or in very dry conditions. They can germinate on piles of leaf litter, on bare mineral soil, in cracks in sidewalks and driveways, in rain gutters, and even under the windshield wiper blades of a 1990 Geo Prism (personal observation). Ninety percent of the seeds produced can germinate and they are able to do so almost immediately after flying away from the parental tree.

The small seeds in their samaras can fly great distances in a strong wind. Any area with red maple trees will fill up with red maple seeds and seedlings, and this system saturation will be renewed each year! Most of the first year seedlings will not survive, but since there are so many of them each, and since each passing year adds countless more to the population, in a short period of time the forest understory will be full of red maples.

What is the nature of the competition and stress matrix affecting a red maple seedling?  First of all, there are the thousands of other red maple seedlings. For an individual seedling to prevail its genetic make-up and physiological potential must match up with the restrictions and factors of its environment.  Many studies have described the broad genetic range of red maple populations: different genetic types are found (and, therefore, have succeeded) in wet lowlands and in dry ridge ecosystems. Root growth patterns in these extreme sites are different (deep roots are favored in dry sites but shallow, spreading roots are favored in wet). Secondly, the seedling’s energy potentials must match the restrictions of its site. If it is in the deep shade of a closed canopy forest, the seedling must be able to live at low photosynthetic activity (and comparably low respiratory and growth activity) for many years. If the seedling is out in the full sun, it must be able to handle the large energy input of the full sun exposure and the potentially dry conditions that full sunlight exposure might generate.

(Next week: deer and red maples, a complex symbiosis!)

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