LIFE IN THE LOWER SUSQUEHANNA RIVER WATERSHED
A Natural History of Conewago Falls—The Waters of Three Mile Island
During one of the interludes between yesterday’s series of thunderstorms and rain showers, we had a chance to visit a wooded picnic spot to devour a little snack. Having packed lite fare, there wasn’t enough to share. Fortunately, pest control wasn’t a concern. It was handled for us…
After enjoying our little luncheon and watching all the sideshows, it was time to cautiously make our way home,…
Homo sapiens owes much of its success as a species to an acquired knowledge of how to make, control, and utilize fire. Using fire to convert the energy stored in combustible materials into light and heat has enabled humankind to expand its range throughout the globe. Indeed, humans in their furless incomplete mammalian state may have never been able to expand their populations outside of tropical latitudes without mastery of fire. It is fire that has enabled man to exploit more of the earth’s resources than any other species. From cooking otherwise unpalatable foods to powering the modern industrial society, fire has set man apart from the rest of the natural world.
In our modern civilizations, we generally look at the unplanned outbreak of fire as a catastrophe requiring our immediate intercession. A building fire, for example, is extinguished as quickly as possible to save lives and property. And fires detected in fields, brush, and woodlands are promptly controlled to prevent their exponential growth. But has fire gone to our heads? Do we have an anthropocentric view of fire? Aren’t there naturally occurring fires that are essential to the health of some of the world’s ecosystems? And to our own safety? Indeed there are. And many species and the ecosystems they inhabit rely on the periodic occurrence of fire to maintain their health and vigor.
Man has been availed of the direct benefits of fire for possibly 40,000 years or more. Here in the Lower Susquehanna River Watershed, the earliest humans arrived as early as 12,000 years ago—already possessing skills for using fire. Native plants and animals on the other hand, have been part of the ever-changing mix of ecosystems found here for a much longer period of time—millions to tens of millions of years. Many terrestrial native species are adapted to the periodic occurrence of fire. Some, in fact, require it. Most upland ecosystems need an occasional dose of fire, usually ignited by lightning (though volcanism and incoming cosmic projectiles are rare possibilities), to regenerate vegetation, release nutrients, and maintain certain non-climax habitat types.
But much of our region has been deprived of natural-type fires since the time of the clearcutting of the virgin forests during the eighteenth and nineteenth centuries. This absence of a natural fire cycle has contributed to degradation and/or elimination of many forest and non-forest habitats. Without fire, a dangerous stockpile of combustible debris has been collecting, season after season, in some areas for a hundred years or more. Lacking periodic fires or sufficient moisture to sustain prompt decomposition of dead material, wildlands can accumulate enough leaf litter, thatch, dry brush, tinder, and fallen wood to fuel monumentally large forest fires—fires similar to those recently engulfing some areas of the American west. So elimination of natural fire isn’t just a problem for native plants and animals, its a potential problem for humans as well.
To address the habitat ailments caused by a lack of natural fires, federal, state, and local conservation agencies are adopting the practice of “prescribed fire” as a treatment to restore ecosystem health. A prescribed fire is a controlled burn specifically planned to correct one or more vegetative management problems on a given parcel of land. In the Lower Susquehanna River Watershed, prescribed fire is used to…
Let’s look at some examples of prescribed fire being implemented right here in our own neighborhood…
In Pennsylvania, state law provides landowners and crews conducting prescribed fire burns with reduced legal liability when the latter meet certain educational, planning, and operational requirements. This law may help encourage more widespread application of prescribed fire in the state’s forests and other ecosystems where essential periodic fire has been absent for so very long. Currently in the Lower Susquehanna River Watershed, prescribed fire is most frequently being employed by state agencies on state lands—in particular, the Department of Conservation and Natural Resources on State Forests and the Pennsylvania Game Commission on State Game Lands. Prescribed fire is also part of the vegetation management plan at Fort Indiantown Gap Military Reservation and on the land holdings of the Hershey Trust. Visitors to the nearby Gettysburg National Military Park will also notice prescribed fire being used to maintain the grassland restorations there.
For crews administering prescribed fire burns, late March and early April are a busy time. The relative humidity is often at its lowest level of the year, so the probability of ignition of previous years’ growth is generally at its best. We visited with a crew administering a prescribed fire at Middle Creek Wildlife Management Area last week. Have a look…
Prescribed burns aren’t a cure-all for what ails a troubled forest or other ecosystem, but they can be an effective remedy for deficiencies caused by a lack of periodic episodes of naturally occurring fire. They are an important option for modern foresters, wildlife managers, and other conservationists.
To take advantage of this unusually mild late-winter day, observers arrived by the thousands to have a look at an even greater number of migratory birds gathered at the Pennsylvania Game Commission’s Middle Creek Wildlife Management Area. Here are some highlights…
During the past two weeks, over 150 American Flamingos (Phoenicopterus ruber) have been reported in the eastern half of the United States, well north of their usual range—northern South America; Cuba, the Bahamas, and other Caribbean Islands; and the Yucatan Peninsula of Mexico. They are also found on the Galapagos Islands. Prior to being extirpated by hunting during the early years of the twentieth century, American Flamingos nested in the Everglades of Florida as well.
The recent influx of these tropical vagrants into the eastern states is attributed to Hurricane Idalia, a storm that formed in the midst of flamingo territory during the final week of August. Idalia got its start over tropical waters off Yucatan before progressing north through the Gulf of Mexico off Cuba to make landfall in the “Big Bend” area of Florida.
Birds of warm water seas regularly become entangled within tropical storms and hurricanes. In most cases, it’s oceanic seabirds including petrels, shearwaters, terns, and gulls that seek refuge from turbulent conditions by remaining inside the storm’s eye or within the margins of the rotating bands. The duration of the experience and the fitness of each individual bird may determine just how many survive such an ordeal. As a storm makes landfall, the survivors put down on inland bodies of water, often in unexpected places hundreds of miles from the nearest coastline. Some may linger in these far-flung areas to feed and gain strength before finding their way down rivers back to sea.
For birds like American Flamingos, which don’t spend a large portion of their lives on the wing over vast oceanic waters, becoming entangled in a tropical weather system can easily be a life-ending event. American Flamingos, despite their size and lanky appearance, are quite agile fliers. When necessary, some populations travel significant distances in search of new food sources. Some closely related migratory species of flamingos have been recorded at altitudes exceeding 10,000 feet. But becoming trapped in a hurricane for an extended period of time could easily erode the endurance of even the strongest of fliers. And once out over open water, there’s nowhere for a flamingo to come down for a rest.
It appears probable that, during the final week of August, hundreds of American Flamingos did find themselves drawn away from their familiar tidal flats and salty lagoons to be swept into the spinning clouds and gusty downpours of Hurricane Idalia as it churned off the Yucatan coast. Despite the dangers, more than 150 of them completed a journey within its clutches to cross the Gulf of Mexico and land in the Eastern United States.
Amy Davis in a report for the American Birding Association compiled a list of American Flamingo sightings from the days following the landfall of Hurricane Idalia. We’ve plotted those sightings on a satellite image of the storm.
The majority of the flamingos that survived this harrowing trip found a place to put down along the coast. But as the reader will notice, a significant number of the sightings were outside the path of the storm in areas not reached by even the outermost bands of clouds. Flamingos in Alabama, Tennessee, Kentucky/Indiana, Ohio, and Pennsylvania were found at inland bodies of water, most on the days immediately following the storm’s landfall. The lone exception, the Pennsylvania birds, were discovered a week after landfall (but may have been there days longer). How and why did these birds find their way so far inland at places so distant from the storm…and home? And how did they get there so quickly? The counterclockwise rotation of the hurricane wouldn’t slingshot them in that direction, would it?
Let’s have a look at the surface map showing us the weather in the states outside the direct influence of Hurricane Idalia during the storm’s landfall on August 30, 2023…
Now check out this satellite view of the storm during the hours following landfall…
Click the image above to play a GIF animation of GOES-16 satellite photos showing Idalia after landfall and the strong “flamingo highway” winds between the fronts. (It’s a big file, so give it a little time to load.) You’ll also note the ferocious lightning associated with both Huricane Idalia and Hurricane Franklin.
Did the inland flamingos catch a ride on these stiff “flamingo highway” winds? If not, they may have had a little help from a high pressure ridge that became established over the southern Appalachians as Idalia crept out to sea. The clockwise rotation of this ridge kept a similar flow over the “flamingo highway” for much of the four days that followed.
For vagrant birds including those carried away to distant lands by hurricanes and other storms, the challenges of finding food and avoiding hazards including disease, unfamiliar predators, and extreme weather can be a matter of life and death. For American Flamingos now loafing and feeding in the Eastern United States outside Florida, the hardest part of their journey is yet to come. They need to find their way back south to suitable tropical habitat before cold weather sets in. The perils are many. Theirs is not an enviable predicament.
Have you purchased your 2023-2024 Federal Duck Stamp? Nearly every penny of the 25 dollars you spend for a duck stamp goes toward habitat acquisition and improvements for waterfowl and the hundreds of other animal species that use wetlands for breeding, feeding, and as migration stopover points. Duck stamps aren’t just for hunters, purchasers get free admission to National Wildlife Refuges all over the United States. So do something good for conservation—stop by your local post office and get your Federal Duck Stamp.
Still not convinced that a Federal Duck Stamp is worth the money? Well then, follow along as we take a photo tour of Bombay Hook National Wildlife Refuge. Numbers of southbound shorebirds are on the rise in the refuge’s saltwater marshes and freshwater pools, so we timed a visit earlier this week to coincide with a late-morning high tide.
As the tide recedes, shorebirds leave the freshwater pools to begin feeding on the vast mudflats exposed within the saltwater marshes. Most birds are far from view, but that won’t stop a dedicated observer from finding other spectacular creatures on the bay side of the tour route road.
No visit to Bombay Hook is complete without at least a quick loop through the upland habitats at the far end of the tour route.
We hope you’ve been convinced to visit Bombay Hook National Wildlife Refuge sometime soon. And we hope too that you’ll help fund additional conservation acquisitions and improvements by visiting your local post office and buying a Federal Duck Stamp.
Along the lower Susquehanna, an unseasonably mild day in early spring can provide an observer with the opportunity to witness an annual spectacle seldom seen by the average visitor to the river—concentrations of dozens, sometimes hundreds, of turtles as they emerge from their winter slumber to bathe in the year’s first surge of warm air and sunshine.
Let’s take a quiet stroll through the forest to have a look around. The spring awakening is underway and it’s a marvelous thing to behold. You may think it a bit odd, but during this walk we’re not going to spend all of our time gazing up into the trees. Instead, we’re going to investigate the happenings at ground level—life on the forest floor.
There certainly is more to a forest than the living trees. If you’re hiking through a grove of timber getting snared in a maze of prickly Multiflora Rose (Rosa multiflora) and seeing little else but maybe a wild ungulate or two, then you’re in a has-been forest. Logging, firewood collection, fragmentation, and other man-made disturbances inside and near forests take a collective toll on their composition, eventually turning them to mere woodlots. Go enjoy the forests of the lower Susquehanna valley while you still can. And remember to do it gently; we’re losing quality as well as quantity right now—so tread softly.
So you aren’t particularly interested in a stroll through the Pennsylvania woods during the gasoline and gunpowder gang’s second-biggest holiday of the year—the annual sacrifice-of-the-White-tailed-Deity ritual. I get it. Two weeks and nothing to do. Well, why not try a hike through the city instead? I’m not kidding. You might be surprised at what you see. Here are some photographs taken today during several strolls in Harrisburg, Pennsylvania.
First stop was City Island in the Susquehanna River—accessible from downtown Harrisburg or the river’s west shore by way of the Market Street Bridge.
Okay, City Island was worth the effort. Next stop is Wildwood Park, located along Industrial Road just north of the Pennsylvania Farm Show complex and the Harrisburg Area Community College (HACC) campus. There are six miles of trails surrounding mile-long Wildwood Lake within this marvelous Dauphin County Parks Department property.
And now, without further ado, it’s time for the waterfowl of Wildwood Lake—in order of their occurrence.
See, you don’t have to cloak yourself in bright orange ceremonial garments just to go for a hike. Go put on your walking shoes and a warm coat, grab your binoculars and/or camera, and have a look at wildlife in a city near you. You never know what you might find.
SOURCES
Taylor, Scott A., Thomas A. White, Wesley M. Hochachka, Valentina Ferretti, Robert L. Curry, and Irby Lovette. 2014. “Climate-Mediated Movement of an Avian Hybrid Zone”. Current Biology. 24:6 pp.671-676.
The humid rainy remains of Hurricane Nate have long since passed by Pennsylvania, yet mild wet weather lingers to confuse one’s sense of the seasons. This gloomy misty day was less than spectacular for watching migrating birds and insects, but some did pass by. Many resident animals of the falls are availing themselves of the opportunity to continue active behavior before the cold winds of autumn and winter force a change of lifestyle.
Warm drizzle at daybreak prompted several Northern Spring Peepers (Pseudacris crucifer crucifer) to begin calling from the wetlands in the Riparian Woodlands of Conewago Falls. An enormous chorus of these calls normally begins with the first warm rains of early spring to usher in this tiny frog’s mating season. Today, it was just a few “peeps” among anxious friends.
Any additional river flow that resulted from the rains of the previous week is scarcely noticeable among the Pothole Rocks. The water level remains low, the water column is fairly clear, and the water temperatures are in the 60s Fahrenheit.
It’s no real surprise then to see aquatic turtles climbing onto the boulders in the falls to enjoy a little warmth, if not from the sun, then from the stored heat in the rocks. As usual, they’re quick to slide into the depths soon after sensing someone approaching or moving nearby. Seldom found anywhere but on the river, these skilled divers are Common Map Turtles (Graptemys geographica), also known as Northern Map Turtles. Their paddle-like feet are well adapted to swimming in strong current. They are benthic feeders, feasting upon a wide variety of invertebrates found among the stone and substrate of the river bottom.
Adult Common Map Turtles hibernate communally on the river bottom in a location protected from ice scour and turbulent flow, often using boulders, logs, or other structures as shelter from strong current. The oxygenation of waters tumbling through Conewago Falls may be critical to the survival of the turtles overwintering downstream. Dissolved oxygen in the water is absorbed by the nearly inactive turtles as they remain submerged at their hideout through the winter. Though Common Map Turtles, particularly males, may occasionally move about in their hibernation location, they are not seen coming to the surface to breathe.
The Common Map Turtles in the Susquehanna River basin are a population disconnected from that found in the main range of the species in the Great Lakes and upper Mississippi basin. Another isolated population exists in the Delaware River.
SOURCES
Committee on the Status of Endangered Wildlife in Canada. 2002. Status Report of the Northern Map Turtle. Canadian Wildlife Service. Ottawa, Ontario.