Fire and Ice at Conewago Falls

This morning, the Lower Susquehanna River Watershed experienced remotely the effects of fire and ice.

At daybreak, the cold air mass that brought the first freeze of the season to northernmost New England gave us a taste of the cold with temperatures below 50 degrees throughout.

The air temperature at daybreak in the Gettysburg Basin east of Conewago Falls.

At sunrise, the cloudless sky had a peculiar overcast look with no warm glow on buildings, vegetation, and terrain.  Soon, the sun was well above the horizon, yet there was still a sort of darkness across the landscape.

Smoke from massive wildland fires in the Pacific Coast States created a haze that persisted throughout the day in the Susquehanna valley.
Away from traffic and the odors of agriculture and urban life, the smell of wood smoke was easily detectable.  The haze from fires almost 3,000 miles away made it appear to be an overcast day at Conewago Falls.
Due to the sudden cold, there were no insects flying above the Susquehanna during the first hour of daylight this morning, so swallows gathered in the trees to conserve energy until the hunt would be more productive.
The diabase boulders at Conewago Falls retain heat and provide an even better refuge from the cold than a dead tree on a chilly morning.  Here, a juvenile and an adult Tree Swallow (center) are surrounded by Northern Rough-winged Swallows.  Hundreds of each of these migratory species were feeding at the falls today.
Two dozen or more Barn Swallows, including this juvenile, were seen among the swarming birds.
Several late Bank Swallows, including this one (bottom center), were among the flocks of migrants at Conewago Falls this morning.  One Cliff Swallow (Petrochelidon pyrrhonota) was seen as well.
A Great Egret (Ardea alba) and a Great Blue Heron.
An Osprey searching the clear pools and rapids for a morning meal.
A juvenile Bald Eagle with the same goal in mind.
The same Bald Eagle keeping a close watch on the Osprey.  Bald Eagles frequently ambush Ospreys to steal their catch.  For a young eagle, acquiring the skill of fish theft may improve its chances of survival, at least until the Ospreys head south.

All that bright filtered sunlight was ideal for photographing butterflies along the Conewago Falls shoreline.  Have a look.

During the late morning, dozens of Monarch butterflies migrated past Conewago Falls.  This one paused to feed.
The Viceroy (Limenitis archippus) is a Monarch mimic.  Its appearance fools would-be predators into thinking it is a Monarch and possesses the same foul flavor as the milkweed-raised model.
This Variegated Fritillary (Euptoieta claudia) was among the late-season butterflies at Conewago Falls.
The Common Buckeye is presently just that, very common on flowers and moist sandy soil around the falls.
The Painted Lady is a regularly-occurring migratory species of butterfly.
The Red Admiral is typically a common to abundant migrant.  So far in 2020, they are scarce in the lower Susquehanna valley. 

Feathered Fallout

The NOAA National Weather Service radar images from last evening provided an indication that there may be a good fallout of birds at daybreak in the lower Susquehanna valley.  The moon was bright, nearly full, and there was a gentle breeze from the north to move the nocturnal migrants along.  The conditions were ideal.

Rising from daytime roosts in New York and Pennsylvania, then streaming south in moonlit skies, migrating birds are recorded as echoes on this post-sunset composite NEXRAD loop from last evening.  (NOAA/National Weather Service image)

The Riparian Woodlands at Conewago Falls were alive with migrants this morning.  American Robins and White-throated Sparrows were joined by new arrivals for the season: Brown Creeper (Certhia americana), Ruby-crowned Kinglets (Regulus calendula), Golden-crowned Kinglets (Regulus satrapa), Dark-eyed Junco (Junco hyemalis), and Yellow-rumped Warbler (Setophaga coronata).  These are the perching birds one would expect to have comprised the overnight flight.  While the individuals that will remain may not yet be among them, these are the species we will see wintering in the Mid-Atlantic states.  No trip to the tropics for these hardy passerines.

American Robins continued migratory flight into the first hour of daylight this morning.  Their calls are commonly heard at night as migrating individuals pass overhead.
White-throated Sparrows are nocturnal migrants, and are a familiar find on woodland edges and at suburban feeding stations through the winter.
Dark-eyed Juncos, also nocturnal migrants, are common winter residents in the Lower Susquehanna River Watershed, frequently visiting bird feeders.
Heavy rain earlier this week in the Susquehanna River drainage basin has flooded most of the Pothole Rocks; the rapids of Conewago Falls have returned.
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A Quick Getaway

It was a placid morning on Conewago Falls with blue skies dotted every now and then by a small flock of migrating robins or blackbirds.  The jumbled notes of a singing Winter Wren (Troglodytes hiemalis) in the Riparian Woodland softly mixed with the sounds of water spilling over the dam.  The season’s first Wood Ducks (Aix sponsa), Blue-winged Teal (Spatula discors), Herring Gull (Larus argentatus), Horned Larks (Eremophila alpestris), and White-throated Sparrows (Zonotrichia albicollis) were seen.

There was a small ruckus when one of the adult Bald Eagles from a local pair spotted an Osprey passing through carrying a fish.  This eagle’s effort to steal the Osprey’s catch was soon interrupted when an adult eagle from a second pair that has been lingering in the area joined the pursuit.  Two eagles are certainly better than one when it’s time to hustle a skinny little Osprey, don’t you think?

But you see, this just won’t do.  It’s a breach of eagle etiquette, don’t you know?  Soon both pairs of adult eagles were engaged in a noisy dogfight.  It was fussing and cackling and the four eagles going in every direction overhead.  Things calmed down after about five minutes, then a staring match commenced on the crest of the dam with the two pairs of eagles, the “home team” and the “visiting team”, perched about 100 feet from each other.  Soon the pair which seems to be visiting gave up and moved out of the falls for the remainder of the day.  The Osprey, in the meantime, was able to slip away.

In recent weeks, the “home team” pair of Bald Eagles, seen regularly defending territory at Conewago Falls, has been hanging sticks and branched tree limbs on the cross members of the power line tower where they often perch.  They seem only to collect and display these would-be nest materials when the “visiting team” pair is perched in the nearby tower just several hundred yards away…an attempt to intimidate by homesteading.  It appears that with winter and breeding time approaching, territorial behavior is on the increase.

The second migrating Osprey of the day ran the gauntlet of marauding eagles without incident.

In the afternoon, a fresh breeze from the south sent ripples across the waters among the Pothole Rocks.  The updraft on the south face of the diabase ridge on the east shore was like a highway for some migrating hawks, falcons, and vultures.  Black Vultures (Coragyps atratus) and Turkey Vultures streamed off to the south headlong into the wind after leaving the ridge and crossing the river.  A male and female Northern Harrier (Circus hudsonius), ten Red-tailed Hawks, two Red-shouldered Hawks (Buteo lineatus), six Sharp-shinned Hawks, and two Merlins crossed the river and continued along the diabase ridge on the west shore, accessing a strong updraft along its slope to propel their journey further to the southwest.  Four high-flying Bald Eagles migrated through, each following the east river shore downstream and making little use of the ridge except to gain a little altitude while passing by.

(Top and Middle) Turkey Vultures riding the fresh breeze and teetering to-and-fro on up-tilted wings.  This wing posture is known as a dihedral.  (Bottom) More than 100 migrating Black Vultures climbed high on the afternoon breeze to make an oblique crossing of the river and maintain a southbound course.

Late in the afternoon, the local Bald Eagles were again airborne and cackling up a storm.  This time they intercepted an eagle coming down the ridge toward the river and immediately forced the bird to climb if it intended to pass.  It turned out to be the best sighting of the day, and these “home team” eagles found it first.  It was a Golden Eagle (Aquila chrysaetos) in crisp juvenile plumage.  On its first southward voyage, it seemed to linger after climbing high enough for the Bald Eagles to loose concern, then finally selected the ridge route and crossed the river to head off to the southwest.

Ring-billed Gulls began feeding during the afternoon as clouds preceding stormy weather approached.
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Beauties

It’s tough being good-looking and liked by so many.  You’ve got to watch out, because popularity makes you a target.  Others get jealous and begin a crusade to have you neutralized and removed from the spotlight.  They’ll start digging to find your little weaknesses and flaws, then they’ll exploit them to destroy your reputation.  Next thing you know, people look at you as some kind of hideous scoundrel.

Today, bright afternoon sunshine and a profusion of blooming wildflowers coaxed butterflies into action.  It was one of those days when you don’t know where to look first.

A Pearl Crescent (Phyciodes tharos) sipping nectar from Rough Boneset (Eupatorium pilosum) flowers.  Asters (Aster) are the host plants for the larvae of this butterfly.
A Buckeye (Junonia coenia) on Rough Boneset.  Its caterpillars are known to feed on members of the Acanthus family, possibly including the Water Willow (Justicia americana) which is so abundant in Conewago Falls.
Visitors from south of the Mason-Dixon Line arrived on the recent warm winds.  Two Cloudless Sulphurs (Phoebis sennae) patrolled the Riverine Grasslands, especially near the stands of Partridge Pea, a possible host plant.  One is seen here visiting a Halbred-leaved Rose Mallow blossom.  These large yellow butterflies are always a standout.

Purple Loosestrife (Lythrum salicaria) has a bad reputation.  Not native to the Americas, this prolific seed producer began spreading aggressively into many wetlands following its introduction.  It crowds out native plant species and can have a detrimental impact on other aquatic life.  Stands of loosestrife in slow-moving waters can alter flows, trap sediment, and adversely modify the morphology of waterways.  Expensive removal and biological control are often needed to protect critical habitat.

The dastardly Purple Loosestrife may have only two positive attributes.  First, it’s a beautiful plant.  And second, it’s popular; butterflies and other pollinators find it to be irresistible and go wild over the nectar.

A Silver-spotted Skipper (Epargyreus clarus) feeding on Purple Loosestrife nectar.  The host plants for this common butterfly’s caterpillars are a wide variety of Legumes.
A Cabbage White (Pieris rapae), a butterfly introduced from Europe in the 1800s, feeds on introduced Purple Loosestrife.
A Wild Indigo Duskywing (Erynnis baptisiae) feeding on Purple Loosestrife. This butterfly has expanded its population and range by using the introduced Crown Vetch as a host plant.

Don’t you just adore the wonderful butterflies.  Everybody does.  Just don’t tell anyone that they’re pollinating those dirty filthy no-good Purple Loosestrife plants.

SOURCES

Brock, Jim P., and Kenn Kaufman.  2003.  Butterflies of North America.  Houghton Mifflin Company.  New York.

Newcomb, Lawrence.  1977.  Newcomb’s Wildflower Guide.  Little, Brown and Company.  Boston, Massachusetts.