Category: Animals (Animalia)

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Blooming in Early July: Great Rhododendron

With the gasoline and gunpowder gang’s biggest holiday of the year now upon us, wouldn’t it be nice to get away from the noise and the enduring adolescence for just a little while to see something spectacular that isn’t exploding or on fire?  Well, here’s a suggestion: head for the hills to check out the flowers of our native rhododendron, the Great Rhododendron (Rhododendron maximum), also known as Rosebay.

Great Rhododendron
The Great Rhododendron is an evergreen shrub found growing in the forest understory on slopes with consistently moist (mesic) soils.  The large, thick leaves make it easy to identify.  During really cold weather, they may droop and curl, but they still remain green and attached to the plant.

Thickets composed of our native heathers/heaths (Ericaceae) including Great Rhododendron, Mountain Laurel, and Pinxter Flower (Rhododendron periclymenoides), particularly when growing in association with Eastern Hemlock and/or Eastern White Pine, provide critical winter shelter for forest wildlife.  The flowers of native heathers/heaths attract bees and other pollinating insects and those of the deciduous Pinxter Flower, which blooms in May, are a favorite of butterflies and Ruby-throated Hummingbirds.

Pinxter Flower in bloom
A close relative of the Great Rhododendron is the Pinxter Flower, also known as the Pink Azalea.

Forests with understories that include Great Rhododendrons do not respond well to logging.  Although many Great Rhododendrons regenerate after cutting, the loss of consistent moisture levels in the soil due to the absence of a forest canopy during the sunny summertime can, over time, decimate an entire population of plants.  In addition, few rhododendrons are produced by seed, even under optimal conditions.  Great Rhododendron seeds and seedlings are very sensitive to the physical composition of forest substrate and its moisture content during both germination and growth.  A lack of humus, the damp organic matter in soil, nullifies the chances of successful recolonization of a rhododendron understory by seed.  In locations where moisture levels are adequate for their survival and regeneration after logging, impenetrable Great Rhododendron thickets will sometimes come to dominate a site.  These monocultures can, at least in the short term, cause problems for foresters by interrupting the cycle of succession and excluding the reestablishment of native trees.  In the case of forests harboring stands of Great Rhododendron, it can take a long time for a balanced ecological state to return following a disturbance as significant as logging.

Birds of Conewago Falls in the Lower Susquehanna River Watershed: Ruffed Grouse
Ruffed Grouse (Bonasa umbellus) may be particularly sensitive to the loss of winter shelter and travel lanes provided by thickets of Great Rhododendron and other members of the heather/heath family.  (Vintage 35 mm image)

In the lower Susquehanna region, the Great Rhododendron blooms from late June through the middle of July, much later than the ornamental rhododendrons and azaleas found in our gardens.   Set against a backdrop of deep green foliage, the enormous clusters of white flowers are hard to miss.

Great Rhododendron Flower Cluster
Great Rhododendrons sport an attractive blossom cluster.  The colors of the flower, especially the markings found only on the uppermost petal, guide pollinators to the stamens (male organs) and pistil (female organ).
Bumble Bee Pollinating a Great Rhododendron Flower
To this Bumble Bee (Bombus species), the yellowish spots on the uppermost petal of the Great Rhododendron may appear to be clumps of pollen and are thus an irresistible lure.  

In the Lower Susquehanna River Watershed, there are but a few remaining stands of Great Rhododendron.  One of the most extensive populations is in the Ridge and Valley Province on the north side of Second Mountain along Swatara Creek near Ravine (just off Interstate 81) in Schuylkill County, Pennsylvania.  Smaller groves are found in the Piedmont Province in the resort town of Mount Gretna in Lebanon County and in stream ravines along the lower river gorge at the Lancaster Conservancy’s Ferncliff and Wissler’s Run Preserves.  Go have a look.  You’ll be glad you did.

Great Rhododendron along Route 125 near Ravine
Great Rhododendron along Route 125 along the base of the north slope of Second Mountain north of Ravine, Schuylkill County, Pennsylvania.
Great Rhododendron along Swatara Creek
Great Rhododendrons beginning to bloom during the second week of July along Swatara Creek north of Ravine, Schuylkill County, Pennsylvania.  Note how acid mine drainage has stained the rocks in the upper reaches of this tributary of the lower Susquehanna.  Mitigation of leachate pollutants from legacy mines has facilitated the return of over two dozen species of fish to this waterway, but the telltale discoloration of the stream substrate will remain for some time.
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Photo of the Day

Birds of Conewago Falls in the Lower Susquehanna River Watershed: Yellow-crowned Night Herons
You remember the Photo of the Day from back on April 7th, don’t you?  You know, the one with the pair of endangered Yellow-crowned Night Herons at their nest.  Well, meet their kids.
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Same Story, Different Ending

Once upon a time, a great panic spread throughout the lower Susquehanna region.  A destructive mob of invaders was overtaking our verdant land and was sure to decimate all in its path.  Clad in gray and butternut, they came by the thousands.  Flashing their crimson banners, they signaled their arrival at each new waypoint along their route.  The Pennsylvania government called upon the populace to heed the call and turn out in defense of the state.  Small bands of well-intentioned citizens tried in vain to turn back the progress of the hostiles—none succeeded.  But for a cadre of civic-minded elites and some small groups of college professors and their students, few responded to a call to confine the invasion along designated lines of containment.  Word spread quickly throughout the valley that farms had been overrun by waves of the merciless intruders.  Agrarians reported that their orchards had been stripped; they had lost all of the fruits of their labor.  Stories exaggerating the hideous appearance of the approaching aliens struck fear into the faint-of-heart.  The growing sentiment among the terror-stricken residents: this horde must be stopped before pestilence is visited upon everyone in the state!

And so, on the evening of June 28, 1863, just three days before the Battle of Gettysburg, the wooden Susquehanna River bridge at Columbia-Wrightsville was set ablaze just as Brigadier General John B. Gordon’s brigade of the invading Army of Northern Virginia approached the span’s west entrance preparing to cross to the eastern shore.  Thus, the rebel tide was turned away from the Susquehanna at the point some contend to be the authentic “High-water Mark of the Confederacy”.

Just one among an army of Spotted Lanternflies marching westbound across the Susquehanna River on the present-day Columbia-Wrightsville Bridge.  Same story, different ending.          
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Photo of the Day

Damselflies and dragonflies of the Lower Susquehanna River Watershed: Fragile Forktail
Fragile Forktail damselflies have matured from their aquatic nymphal stage (see “Photo of the Day” from April 24, 2022) into flying adults.  This breeding pair in the “wheel position”, male above and female below, were photographed this week along the edge of the pond at the susquehannawildlife.net headquarters.  You can identify the odonates you see during coming weeks by clicking the “Damselflies and Dragonflies” tab at the top of this page.  There, a gallery of images that includes the Lower Susquehanna River Watershed’s most frequently encountered species will be at your fingertips for easy perusal.
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Photo of the Day

Birds of Conewago Falls in the Lower Susquehanna River Watershed: Eastern Bluebird
First thing this morning, this juvenile Eastern Bluebird left the safety of a nest box at the susquehannawildlife.net headquarters.  Its parents remain nearby and will continue watching over and feeding it for a couple of weeks.  Remember to give young birds and animals plenty of space.  Keep your covert cats in the house and your overt dogs on a leash.  And don’t assume that the cute little animals you find need your help, it’s almost always best to just leave them alone.
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Photo of the Day

Birds of Conewago Falls in the Lower Susquehanna River Watershed: Great Horned Owl
This juvenile Great Horned Owl and its sibling have attained their first set of flight feathers and left the nest.  The duo is still being watched and fed by their parents, which remain hidden in a nearby woodlot.
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Photo of the Day

Birds of Conewago Falls in the Lower Susquehanna River Watershed: "Taiga Merlin"
A “Taiga Merlin” (Falco columbarius columbarius) with an Eastern Kingbird snatched from midair.  Both these species are accomplished fliers that rely upon aerial pursuit to catch their prey, the former preferring small birds and the latter flying insects.
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Birds of Conewago Falls in the Lower Susquehanna River Watershed: Yellow-throated Vireo
A Yellow-throated Vireo (Vireo flavifrons) in a Shagbark Hickory (Carya ovata) along the Conewago Creek east of Conewago Falls.  This Neotropical migrant nests sparingly along stream courses throughout the Lower Susquehanna River Watershed.
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Birds of Conewago Falls in the Lower Susquehanna River Watershed: Common Yellowthroat
The Common Yellowthroat is one of our most frequently encountered warblers.  It can be found in almost any shrubby habitat, but is particularly numerous in streamside and wetland thickets.  Many remain through the summer to nest and raise young.
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Birds of Conewago Falls in the Lower Susquehanna River Watershed: Yellow-throated Warbler
A Yellow-throated Warbler (Setophaga dominica) searches for insects among the branches of a flowering Black Walnut (Juglans nigra).  In river bottomlands, they nest almost exclusively in the canopy of massive Eastern Sycamores trees.  In mature mountain forests, they also use pines.  The Lower Susquehanna River Watershed is located along the northern extreme of the Yellow-throated Warbler’s regular breeding range.  
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Birds of Conewago Falls in the Lower Susquehanna River Watershed: Great Crested Flycatcher
Great Crested Flycatchers (Myiarchus crinitus) are arriving now in forests throughout the lower Susquehanna valley.  Those that don’t pass through will stay to nest in tree cavities including old woodpecker excavations, so let those snags standing!
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Photo of the Day

The Blue-winged Warbler is a Neotropical migrant that nests among successional growth near taller timber in scattered locations throughout the Lower Susquehanna River Watershed.  Its song, a ringing “beee-bzzz”, is one of the easiest in the warbler family repertoire to recognize and remember.  The Blue-winged Warbler has become less widespread as a breeding species as forests and woodlots have matured and utility right-of-ways are sprayed or cleared of shrubs and small trees with greater frequency.
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Photo of the Day

Birds of Conewago Falls in the Lower Susquehanna River Watershed: Northern Parula
The Northern Parula is a Neotropical migrant that nests in mature forest trees along the lower Susquehanna.  It is a warbler most often located by listening for its buzzy song, “zzzzzzzup”, then searching the treetops in the area with hope of detecting its movements there.
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Photo of the Day

Birds of Conewago Falls in the Lower Susquehanna River Watershed: Blackburnian Warbler
The Blackburnian Warbler, a Neotropical migrant, feeds high in the canopy of mature forests during stopovers in the Lower Susquehanna River Watershed, so you need to look up to find one.  This male was seen searching for insects along the branches of an American Beech (Fagus grandifolia).
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Mollusks of the Lower Susquehanna River Watershed: Gray Garden Slug
The Gray Garden Slug (Deroceras reticulatum) is an invasive inhabitant of places subjected to human disturbance, especially cultivated farmland and, as the common name suggests, gardens.  They are most active at night, hiding beneath plant litter, trash, and rocks during the daytime.  This inch-long specimen was photographed while out and about on a recent dreary and damp afternoon.  Natural enemies of terrestrial slugs include birds, toads, frogs, snakes, and some beetles in the family Caribidae.  In the field and vegetable patch, keeping leaf litter and other debris away from the base of young plants can reduce damage caused by these hungry mollusks.
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Photo of the Day

Birds of Conewago Falls in the Lower Susquehanna River Watershed: Rusty Blackbird
In spring, the majority of migrating Rusty Blackbirds move north through the lower Susquehanna basin in late March and April.  Some, like this female seen yesterday along a forested tributary of Conewago Creek east of Conewago Falls, linger into May.  Because it is almost exclusively a denizen of wet bottomlands, the Rusty Blackbird is the least numerous of the regularly occurring blackbirds in our region.
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Birds of Conewago Falls in the Lower Susquehanna River Watershed: Yellow-rumped Warbler
The handsome Yellow-rumped Warbler is one of the earliest and most numerous of the warblers to migrate through the Lower Susquehanna River Watershed each spring.  Look for them now in woodlots and forests throughout the area.
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Early May Migration

National Weather Service radar showed a sizeable nocturnal flight of migrating birds early this morning.  Let’s go for a short stroll and see what’s around.

Radar returns from State College, Pennsylvania, display several bands of light rain and a massive flight of migrating birds.  (NOAA/National Weather Service image)
Birds of Conewago Falls in the Lower Susquehanna River Watershed: Gray Catbird
After coming in on an overnight flight, Gray Catbirds were numerous at dawn this morning.
Birds of Conewago Falls in the Lower Susquehanna River Watershed: Black-and-white Warbler
Masses of Neotropical migrants are just beginning to arrive.  This Black-and-white Warbler was found feeding on insects in a Green Ash tree that, so far, has survived Emerald Ash Borer (Agrilus planipennis) infestation.
Birds of Conewago Falls in the Lower Susquehanna River Watershed: Veery
The Veery is a Neotropical thrush that nests in understory vegetation on forested slopes in the Lower Susquehanna River Watershed.
Birds of Conewago Falls in the Lower Susquehanna River Watershed: Orchard Oriole
Orchard Orioles are here.
Birds of Conewago Falls in the Lower Susquehanna River Watershed: Baltimore Oriole
And Baltimore Orioles are here too.  Vibrant colors like these are what many observers find so wonderful about many of the Neotropical species.
Birds of Conewago Falls in the Lower Susquehanna River Watershed: Double-crested Cormorants
Not all migrants move at night.  While you’re out and about, keep an eye on the sky for diurnal fliers like these migrating Double-crested Cormorants, seen this morning a full ten miles east of the river.
Birds of Conewago Falls in the Lower Susquehanna River Watershed: Carolina Wren
While many birds are still working their way north to their breeding grounds, resident species like this Carolina Wren are already feeding young.  This one has collected a spider for its nestlings.
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Photo of the Day

Dragonflies and Damselflies of the Lower Susquehanna River Watershed: Fragile Forktail nymph
The aquatic larval stage of a damselfly is commonly known as a nymph.  It feeds on small underwater invertebrates, then, as an adult, transitions to grabbing flying insects in midair.  While many species inhabit streams, Fragile Forktail (Ischnura posita) nymphs are found primarily in wetlands and small pools of water. This one was produced from eggs laid last summer among submerged vegetation in the susquehannawildlife.net headquarters pond.  In just a few weeks, it will climb a stem or cluster of leaves and transform into a colorful adult-stage damselfly known as an imago.  To see a photo gallery featuring this and other species of odonates found in the Lower Susquehanna River Watershed, click on the “Damselflies and Dragonflies” tab at the top of this page.
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Spiders of the Lower Susquehanna River Watershed: "Tiger" Wolf Spider
A “Tiger” Wolf Spider (Tigrosa species) lurks beneath the doorstep at the susquehannawildlife.net headquarters.  These arachnids reach only about one inch in length but appear startlingly larger due to their husky build.  To feed, Wolf Spiders spin no web for snagging flying insects.  Instead, they keep watch with their eight eyes, then ambush or chase down suitable prey.  If handled roughly or pinched between an object such as a shoe and your skin, Wolf Spiders can inject a sore-producing venom.  We like having them around our entranceway, just to keep a few eyes on things.
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Photo of the Day

Invasive Trees and Plants of the Lower Susquehanna River Watershed: Callery Pear including Bradford Pear
Presently in the valleys of the Lower Susquehanna River Watershed, you’re sure to see a gorgeous nightmare, showy stands of flowering Callery Pear (Pyrus calleryana).  Invasive groves like this one quickly dominate successional habitat and often create monocultures, often excluding native pioneer trees like Eastern Red Cedar and several species of deciduous hardwood.  The void beneath the pear trees in this photograph shows how deer browsing can intensify the damage, preventing other plant species from becoming established in the understory.  In autumn, crimson foliage again makes these non-native trees a standout in the landscape.  The red leaves attract birds including American Robins and Cedar Waxwings to the abundant berries, but European Starlings usually get to them first.  Planted specimens of ornamental Callery Pears began producing fertile seeds when multiple varieties became available in addition to the self-sterile “Bradford Pears” that were planted widely during the last decades of the twentieth century.  Cross-pollination between varieties produces the fertile seeds that are distributed by starlings and other birds as they digest the fruit.
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Emergence of the Turtles

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.

Reptiles of the Lower Susquehanna River Watershed: Snapping Turtle
Snapping Turtles (Chelydra serpentina) spend the winter buried in mud along the river shoreline and in nearby Alluvial Terrace Wetlands.  We photographed this one just as it was digging its way out.
Reptiles of the Lower Susquehanna River Watershed: Snapping Turtle
A cold and stiff Snapping Turtle crawls away from the shade toward sun-drenched shallows where it will have a chance to limber up.
Reptiles of the Lower Susquehanna River Watershed: Snapping Turtle
A cruise in open water loosens up the muscles and gets rid of some of the accumulations of sticky mud and muck.
Reptiles of the Lower Susquehanna River Watershed: Painted Turtles
Freshly emerged Painted Turtles clamber onto a log to bask in the cloud-filtered sun.
Reptiles of the Lower Susquehanna River Watershed: Painted Turtle atop a Snapping Turtle
A Painted Turtle looking for a place to get out of the chilly water soon discovered the obvious solution.
It’s catching on, more Painted Turtles atop a Snapping Turtle in an Alluvial Terrace Wetland.
Reptiles of the Lower Susquehanna River Watershed: Red-eared Slider and Common Map Turtle
The Common Map Turtle (right) is the turtle most frequently observed basking on rocks and logs along the main stem of the Susquehanna.  To the left is a Red-eared Slider (Trachemys scripta elegans), an increasingly numerous invasive species.  The first Red-eared Sliders arrived in the river as, you guessed it, unwanted pets.  Editor’s Note: Special thanks to the local North American Beaver (Castor canadensis) for trimming the trees and providing a clear shot for this photograph!
Reptiles of the Lower Susquehanna River Watershed: Red-eared Slider and Painted Turtles
And now, a quick quiz.  Name the things that don’t belong in this picture?  Here’s a hint: a non-native Red-eared Slider (left) joins indigenous Painted Turtles atop a discarded tire in an Alluvial Terrace Wetland in Dauphin County, Pennsylvania.
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Birds of Conewago Falls in the Lower Susquehanna River Watershed: Great Egret
During the late nineteenth century, Great Egrets were nearly exterminated by hunters who shot adult birds, often at their nest sites, to collect the ornate plumes that adorn their heads and backs during breeding season.  Parentless young were left to die in the nests while the showy feathers of the adults were sold to clothiers as decorations for expensive hats.  In Pennsylvania, the Great Egret nests at just a few locations and is listed as an endangered species.  
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Birds of Conewago Falls in the Lower Susquehanna River Watershed: Yellow-crowned Night Heron
In the urban landscape, massive old trees like this Eastern Sycamore not only provide shade and beauty, but they can also be essential nesting sites for birds like these Yellow-crowned Night Herons, a species listed as endangered in Pennsylvania.  This pair is part of a small colony located in the stylish midtown section of the state’s capital city, Harrisburg.
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Photo of the Day

Birds of Conewago Falls in the Lower Susquehanna River Watershed: American Bittern
The American Bittern (Botaurus lentiginosus) is a member of the Ardeidae, the heron and egret family.  It is a stealthy migrant, making its flights under cover of darkness, then resting and feeding in dense stands of Common Cattails and other marsh plants during the day.  It avoids detection by raising its bill skyward to create a profile and color scheme that blends well with the contours of the vegetation.  In Pennsylvania, loss of wetland habitat used for nesting has led to the American Bittern being listed as an endangered species.
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An Encore of the Susquehanna Seawatch

In late March and early April, a rainy night and fog at daybreak can lead to an ideal morning for spotting migratory waterfowl and seabirds during their layover on the lower Susquehanna.  Visibility was just good enough to spot these birds at Harrisburg, Pennsylvania, most of them feeding at midriver.

Northern Shovelers are regular migrants, more often seen on ponds and in wetlands than on the river.
A pair of American Wigeons head upriver.
A Horned Grebe.
A small flock of northbound Buffleheads.
Ring-necked Ducks.
Lesser Scaup, eight of the more than 100 seen along Front Street in Harrisburg at the Pennsylvania Governor’s Residence.  Note how the white bar on the wing’s secondaries becomes diffused and dusky in the primaries.
Lesser Scaup spend the winter on bays and lakes to our south.
More Scaup, the lead bird with bright white extending through the secondaries into the primaries is possibly a Greater Scaup (Aythya marila).
Long-tailed Ducks, formerly known as Oldsquaw, are a diving duck that winters on the Great Lakes and on bays along the Atlantic Coast.  They nest on freshwater ponds and lakes in the tundra of Canada and Alaska.
A male Common Merganser.
This pair of Hooded Mergansers may be nesting in a tree cavity nearby.
The local Peregrine Falcon grabbed a passing Common Grackle…
…prompting the more than 100 Bonaparte’s Gulls in the vicinity to quickly depart and fly upstream.
Birds of Conewago Falls in the Lower Susquehanna River Watershed: Northern Flicker
It pays to keep an eye on the trees along the shoreline too.  Migrants like this Northern Flicker are beginning to come through in numbers.
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