Chesapeake Bay Maritime Accidents and Their Impact on Susquehanna Wildlife

Tuesday’s collision of the container ship Dali into Baltimore’s Francis Scott Key Bridge and the nearly immediate collapse of the span into the chilly waters below reminds us just how unforgiving and deadly maritime accidents can be.  Upon termination of rescue and recovery operations, salvage and cleanup will be prioritized as the next steps in the long-term process of reopening the navigable waters to ship traffic and construction of a new bridge.  Part of the effort will include monitoring for leaks of fuels and other hazardous materials from the ship, its damaged cargo containers, and vehicles and equipment that were on the bridge when it failed.

Damage to the hull of the Dali and to the cargo containers on her deck could lead to leaks of hazardous liquids or other materials into Chesapeake Bay.  (United States Army Corps of Engineers Baltimore image)

On the waters and shores of today’s Chesapeake, numerous county, state, and federal agencies, including the United States Coast Guard, monitor and inspect looking for conditions and situations that could lead to point-source or accidental discharges of petroleum products and other hazardous materials into the bay.  Many are trained, equipped, and organized for emergency response to contain and mitigate spills upon detection.  But this was not always the case.

Through much of the twentieth century, maritime spills of oil and other chemicals magnified the effects of routine discharges of hazardous materials and sanitary sewer effluent into the Chesapeake and its tributaries.  The cumulative effect of these pollutants progressively impaired fisheries and bay ecosystems leading to noticeable declines in numbers of many aquatic species.  Rather frequently, spills or discharges resulted in conspicuous fish and/or bird kills.

One of the worst spills occurred near the mouth of the Potomac River on February 2, 1976, when a barge carrying 250,000 gallons of number 6 oil sank in a storm and lost its cargo into the bay.  During a month-long cleanup, the United States Coast Guard recovered approximately 167,000 gallons of the spilled oil, the remainder dispersed into the environment.  A survey counted 8,469 “sea ducks” killed.  Of the total number, the great majority were Horned Grebes (4,347 or 51.3%) and Long-tailed Ducks (2,959 or 34.9%).  Other species included Surf Scoter (Melanitta perspicillata) (405 or 4.8%), Common Loon (195 or 2.3%), Bufflehead (166 or 2.0%), Ruddy Duck (107 or 1.3%), Common Goldeneye (78 or 0.9%), Tundra Swan (46 or 0.5%), Greater Scaup (19 or 0.2%), American Black Duck (12 or 0.2%), Common Merganser (11 or 0.1%), Canvasback (10 or 0.1%), Double-crested Cormorant (10 or 0.1%), Canada Goose (8 or 0.1%), White-winged Scoter (Melanitta deglandi) (7 or 0.1%), Redhead (5 or 0.1%), gull species (10 or 0.1%), miscellaneous ducks and herons (13 or 0.2%) and unidentified (61 or 0.7%).  During the spring migration, a majority of these birds would have made their way north and passed through the lower Susquehanna valley.  The accident certainly impacted the occurrence of the listed species during that spring in 1976, and possibly for a number of years after.

Horned Grebe during migration on the Susquehanna near Haldeman Riffles.
Of the 8,469 birds killed by the February 2, 1976, oil spill on the Chesapeake, 51.3% (4,347) were Horned Grebes.  Many of them would have migrated north through the Lower Susquehanna River Watershed during the coming spring.

The Federal Water Pollution Control Act Amendments of 1972, commonly known as the Clean Water Act, put teeth into the original FWCPCA of 1948 and began reversing the accumulation of pollutants in the bay and other bodies of water around the nation.  Additional amendments in 1977 and 1987 have strengthened protections and changed the culture of “dump-and-run” disposal and “dilution-is-the-solution” treatment of hazardous wastes.  During the late nineteen-seventies and early nineteen-eighties, emergency response teams and agencies began organizing to control and mitigate spill events.  The result has been a greater awareness and competency for handling accidental discharges of fuels and other chemicals into Chesapeake Bay and other waterways.  These improvements can help minimize the environmental impact of the Dali’s collision with the Francis Scott Key Bridge in Baltimore.

Hickory Shad
Oil spills and other pollution in the Chesapeake can impact populations of migratory fish including the anadromous Hickory Shad which are presently transiting the bay on their way to the waters of the Susquehanna below Conowingo Dam.

SOURCES

Roland, John V., Moore, Glenn E., and Bellanca, Michael A.  1977.  “The Chesapeake Bay Oil Spill—February 2, 1976: A Case History”.  International Oil Spill Conference Proceedings (1977).  1977 (1): 523-527.

Waterfowl on a Rainy Day

Though soggy, windy, and rainy, it happened to be a delightfully mild day to search for migrating waterfowl in the Lower Susquehanna River Watershed.  Here’s a look at what we found temporarily grounded by the poor flight conditions…

Northern Pintails
It’s prime time for northbound Northern Pintails.
American Wigeons and Ring-necked Ducks
This raft of distant waterfowl appears to include mostly American Wigeons and Ring-necked Ducks.
Ring-necked Duck
A much more cooperative drake Ring-necked Duck.
American Black Ducks
A couple of American Black Ducks take a break during an afternoon shower.
Northern Shovelers
A pair of Northern Shovelers in the rain.
Common Mergansers
And a pair of blissful Common Mergansers.
Common Mergansers
Uh oh!…must be something he said.

Migrating Ducks Find Emergency Refuge on the Susquehanna

As anticipated, lakes and ponds throughout the lower Susquehanna basin are beginning to freeze.  Fortunately for the waterfowl thereon, particularly diving ducks, the rain-swollen river is slowly receding and water clarity is improving to provide a suitable alternative to life on the man-made impoundments.

Ice-free Susquehanna at Harrisburg, Pennsylvania
The Susquehanna, ice-free and receding from near flood stage levels last week, can presently provide suitable habitat for diving ducks and other wintering waterfowl.
A Common Merganser on the Susquehanna in Dauphin County, Pennsylvania.
A feeding Common Merganser takes a breather between dives on the Susquehanna in Dauphin County, Pennsylvania.

The deep freeze is not only impacting ponds and lakes in the lower Susquehanna valley, but is evidently affecting the larger bodies of water to our north and northwest.  During Tuesday’s snow event, thousands of diving ducks arrived on the main stem of the river—apparently forced down by the inclement weather while en route to the Atlantic Coast from the Great Lakes and its connected waterways, which are currently beginning to freeze.

Ice-free Susquehanna
Tuesday’s snowfall not only blanketed the landscape with a coating of white,…
Bay Ducks on the Susquehanna
…it prompted thousands of migrating “bay ducks” including Canvasbacks, Redheads, scaup, and other diving species to seek open water and make a forced landing.
Scaup on the Susquehanna
Scaup were by far the most numerous of the birds in the grounded flight.  The majority appeared to be Lesser Scaup.
Scaup in flight.
Scaup in flight on the Susquehanna.
Scaup, Buffleheads, and Long-tailed Duck
A mixed raft of scaup and Buffleheads seen one day after a snowstorm-related fallout of late-season migrants.  A single Long-tailed Duck, a species formerly known as Oldsquaw, can be seen to the lower left.
Scaup, Bufflehead, and Long-tailed Duck
Scaup and a Bufflehead (center) fly past a Long-tailed Duck.  Because they winter primarily in coastal waters, both of the latter species are sometimes categorized as “sea ducks”.
Ruddy Ducks
A small flock of Ruddy Ducks.
Common Mergansers
While Common Mergansers on the Susquehanna are fish eaters (piscivores), other diving ducks observed during this fallout event are primarily benthic feeders, eating plant matter and invertebrate animals collected from the river bottom.
Common Goldeneyes
A small flock of Common Goldeneyes. They, like the Long-tailed Duck and Bufflehead, are sometimes known as a species of “sea duck”.
Scaup and Buffleheads
Another mixed raft of scaup and Buffleheads loafing on the Susquehanna.
Bald Eagle
Large numbers of waterfowl attract the attention of the river’s ever-vigilant Bald Eagles.
Adult Bald Eagle
An adult Bald Eagle patrolling the area of a fallout in search of dead, sick, or injured ducks.  In addition to the victims of naturally occurring ailments, eagles find birds and mammals wounded or killed by hunters to be particularly attractive sources of food.   They can, therefore, quite easily ingest pieces of shot.  Because eagles in the lower Susquehanna valley feed as frequently in upland habitats as they do in riverine environs, use of alternatives to toxic lead shot is prudent practice in all habitat types.
Fourth-year Bald Eagle
A Bald Eagle in the first month of its fourth calendar year.   Though not yet matured to breeding age, this bird is nevertheless smart enough to be on the lookout for vulnerable or deceased waterfowl during a post-storm fallout.
Seeing Some Waterfowl
A fallout of some migrating waterfowl seldom escapes notice by members of the gasoline and gunpowder gang…
Taking Aim at Some Waterfowl
…who find their very presence an irresistible temptation to arouse their adolescent urges…
Harrassing Some Waterfowl
…to get an adrenaline junkie’s fix.

With more snow on the way for tomorrow, you may be wondering if another fallout like this could be in the works.  The only way to find out is to get out there and have a look.  Good luck!  And be good!

Piscivorous Waterfowl Visiting Lakes and Ponds

Heavy rains and snow melt have turned the main stem of the Susquehanna and its larger tributaries into a muddy torrent.  For fish-eating (piscivorous) ducks, the poor visibility in fast-flowing turbid waters forces them to seek better places to dive for food.  With man-made lakes and ponds throughout most of the region still ice-free, waterfowl are taking to these sources of open water until the rivers and streams recede and clear.

Common Mergansers
The Common Merganser is a species of diving duck with a primary winter range that, along the Atlantic Coast, reaches its southern extreme in the lower Susquehanna and Potomac watersheds.  Recently, many have left the main stem of the muddy rivers to congregate on waters with better visibility at some of the area’s larger man-made lakes.
Common Mergansers Feeding
Common Mergansers dive to locate and capture prey, primarily small fish.  During this century, their numbers have declined along the southern edge of their winter range, possibly due to birds remaining to the north on open water, particularly on the Great Lakes.  In the lower Susquehanna valley, some of these cavity-nesting ducks can now be found year-round in areas where heavy timber again provides breeding sites in riparian forests.  After nesting, females lead their young to wander widely along our many miles of larger rivers and streams to feed.
Several Common Mergansers Intimidating a Male with a Freshly Caught Fish
The behavior of these mergansers demonstrates the stiff competition for food that can result when predators are forced away from ideal habitat and become compressed into less favorable space.  On the river, piscivores can feed on the widespread abundance of small fish including different species of minnows, shiners, darters, and more.  In man-made lakes stocked for recreational anglers with sunfish, bass, and other predators (many of them non-native), small forage species are usually nonexistent.  As a result, fish-eating birds can catch larger fish, but are successful far less often.  Seen here are several mergansers resorting to intimidation in an effort to steal a young bass away from the male bird that just surfaced with it.  While being charged by the aggressors, he must quickly swallow his oversize catch or risk losing it.

With a hard freeze on the way, the fight for life will get even more desperate in the coming weeks.  Lakes will ice over and the struggle for food will intensify.  Fortunately for mergansers and other piscivorous waterfowl, high water on the Susquehanna is expected to recede and clarify, allowing them to return to their traditional environs.  Those with the most suitable skills and adaptations to survive until spring will have a chance to breed and pass their vigor on to a new generation of these amazing birds.

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.

Common Goldeneyes, Buffleheads, and Migrating Canada Geese

Spring migration is underway and waterfowl are on the move along the lower Susquehanna River.  Here is a sample of sightings collected during a walk across the Veteran’s Memorial Bridge at Columbia-Wrightsville this morning.

At the Veteran’s Memorial Bridge, the Susquehanna was cresting this morning after recent rains and accompanying snow melt.
An overnight breeze from the southwest and calm winds during the morning hours created ideal conditions for flocks of Canada Geese to begin migrating north from Chesapeake Bay through the lower Susquehanna valley.
These three Common Mergansers and a Common Goldeneye (right) are some of the hundreds of diving ducks presently gathered on the river in the vicinity of the Veteran’s Memorial Bridge.
Common Goldeneyes and a first-winter male Bufflehead (upper right).  All of the ducks seen today in the waters surrounding the bridge are benthic feeders, diving to the river bottom to pluck invertebrates from the substrate.
A male Common Goldeneye (Bucephala clangula).
A female Common Goldeneye.
A pair of Common Goldeneyes in flight.
A pair of Buffleheads in flight.
Common Goldeneyes repositioning for another series of feeding dives.
During the morning flight, thousands of Canada Geese were seen moving north in flocks numbering about 50 to 100 birds each.  The bird in the lower right was one of thousands of Ring-billed Gulls seen headed upriver as well.
As they pass over the lower Susquehanna region, migrating Canada Geese are typically observed flying much higher than flocks from the local resident populations, often reaching the cruising altitudes of aircraft.  Aviators are always alert for flights of resident geese around airfields.  But to prevent bird strikes during days like today when thousands of migratory geese traverse the airspace, air traffic controllers can become extra busy relaying the location and altitude of potential targets to pilots flying aircraft entering areas where birds have been reported.

This is, of course, just the beginning of the great spring migration.  Do make a point of getting out to observe the spectacle.  And remember, keep looking up—you wouldn’t want to miss anything.

Snow Geese Arriving

With plenty of open water on the main lake and no snow cover on the fields where they graze, Snow Geese have begun arriving at Middle Creek Wildlife Management Area in Lancaster/Lebanon Counties.  As long as our mild winter weather continues, more can be expected to begin moving inland from coastal areas to prepare for their spring migration and a return to arctic breeding grounds.

You probably need a break from being indoors all month, so why not get out and have a look?

Hundreds of high-flying Snow Geese descended onto the main lake at Middle Creek Wildlife Management Area this afternoon.
Snow Geese and a few Ring-necked Ducks as seen from the Willow Point observation area at Middle Creek this afternoon.
The sound of calling Tundra Swans is music to the ears on an otherwise quiet winter day.
Dozens of Common Mergansers are at Middle Creek W.M.A. right now.
Look carefully and you might see American Black Ducks among the waterfowl in the refuge’s impoundments.
Northern Shovelers have been at Middle Creek since late fall.  If they can continue to access the muddy bottom of the refuge’s lake for food, they’ll stay until the spring migration.
Check those flocks of Canada Geese carefully, sometimes you’ll find something different among them,…
…like this noticeably smaller bird, probably either a Lesser Canada Goose (Branta canadensis parvipes) or a Richardson’s Cackling Goose (Branta hutchinsii hutchinsii).

Don’t just sit there—don your coat, grab a pair of binoculars, and get out and have a gander!

Looking Up

One can get a stiff neck looking up at the flurry of bird activity in the treetops at this time of year.  Many of the Neotropical migrants favor rich forests as daytime resting sites after flying through the night.  For others, these forests are a destination where they will nest and raise their young.

The Veery (Catharus fuscescens) is a Neotropical thrush that breeds in extensive mature forest on the dampest slopes of the Diabase ridges in the Gettysburg Basin. Their rolling flute-like songs echo through the understory as newly arrived birds establish nesting territories.
The whistled song of the Baltimore Oriole is often heard long before this colorful Neotropical is seen among the foliage of a treetop.  Some dead branches allow us a glimpse of this curious beauty.
The “Pee-a-wee……..Pee-urr” song of the Eastern Wood-Pewee (Contopus virens), a small flycatcher, is presently heard in the Riparian Woodlands at Conewago Falls.  It breeds in forested tracts throughout the lower Susquehanna valley. The vocalizations often continue through the summer, ending only when the birds depart to return to the tropics for the winter.
While constructing a nest beneath a tree canopy, an Eastern Wood-Pewee form-fits the cup where eggs will soon be laid.
The Yellow-billed Cuckoo (Coccyzus americana) nests in the treetops of Riparian Woodlands along the Susquehanna and its tributaries.  Most arrive during the second half of May for their summer stay.  It is a renowned consumer of caterpillars.
The Cedar Waxwing is a notorious wanderer.  Though not a Neotropical migrant, it is a very late nester.  Flocks may continue moving for another month before pairs settle on a place to raise young.
Of the more than twenty species of warblers which regularly migrate through the lower Susquehanna Valley, the Common Yellowthroat (Geothlypis trichas) is among those which breeds here.  It is particularly fond of streamside thickets.

For the birds that arrive earlier in spring than the Neotropical migrants, the breeding season is well underway.  The wet weather may be impacting the success of the early nests.

Northern Rough-winged Swallows arrived back in April.  At traditional nest sites, including the York Haven Dam and local creek bridges, small groups of adults were seen actively feeding and at times perching in dead treetops during recent days.  There was an absence of visits to the actual nest cavities where they should be feeding and fledging young by now.  It’s very possible that these nests failed due to the wet weather and flooding.  Another nest attempt may follow if drier conditions allow stream levels to subside and there is an increase in the mass of flying insects available for the adults to feed to their young..
A Carolina Chickadee, a resident species, is seen atop a hollow stump where it and a mate are constructing a new nest for a second brood.  Did the first brood fail?  Not sure.
Common Mergansers are an uncommon but regular nesting species of waterfowl on the lower Susquehanna River.  They nest in cavities, requiring very large trees to accommodate their needs.  It was therefore encouraging to see this pair on a forested stream in northern Lancaster County during the weekend.  However, a little while after this photograph was taken the pair flew away, indicating that they are not caring for young which by now should be out of the nest and on the move under the watchful care of the female.

So long for now, if you’ll excuse me please, I have a sore neck to tend to.

A Flock of Seagulls?

At the moment there is a heavy snow falling, not an unusual occurrence for mid-February, nevertheless, it is a change in weather.  Forty-eight hours ago we were in the midst of a steady rain and temperatures were in the sixties.  The snow and ice had melted away and a touch of spring was in the air.

Big Bluestem in the Riverine Grasslands is inundated by the rising waters of the Susquehanna at Conewago Falls.   The river ice has been dispersed by the recent mild temperatures and rains.

Anyone casually looking about while outdoors during these last several days may have noticed that birds are indeed beginning to migrate north in the lower Susquehanna valley.  Killdeer, American Robins, Eastern Bluebirds, Red-winged Blackbirds, and Common Grackles are easily seen or heard in most of the area now.

Just hours ago, between nine o’clock this morning and one o’clock this afternoon, there was a spectacular flight of birds following the river north, their spring migration well underway.  In the blue skies above Conewago Falls, a steady parade of Ring-billed Gulls was utilizing thermals and riding a tailwind from the south-southeast to cruise high overhead on a course toward their breeding range.

Ring-billed Gulls swarm in a thermal updraft above Conewago Falls to gain altitude prior to streaming off to the north and continuing their journey.
Ring-billed Gulls climbing to heights sometimes exceeding 1,000 feet before breaking off and gliding away to the north.

The swirling hoards of Ring-billed Gulls attracted other migrants to take advantage of the thermals and glide paths on the breeze.  Right among them were 44 Herring Gulls, 3 Great Black-backed Gulls, 12 Tundra Swans (Cygnus columbianus), 10 Canada Geese, 3 Northern Pintails (Anas acuta), 6 Common Mergansers, 3 Red-tailed Hawks, a Red-shouldered Hawk, 6 Bald Eagles (non-adults), 8 Black Vultures, and 5 Turkey Vultures.

A first-year Herring Gull (top center) is a standout in a “kettle” of Ring-billed Gulls.
How many Ring-billed Gulls passed by today?  More than 18,000…with emphasis on MORE THAN.  You see, early this afternoon, the handy-dandy clicker-counter used to tick off and tally the big flights of birds as they pass by quit clicking and counting.  Therefore, 18,000 is the absolute minimum number of Ring-billed Gulls seen migrating north today.  Hopefully the trusty old oil can will get the clicker working again soon.

In the afternoon, the clouds closed in quickly, the flight ended, and by dusk more than an inch of snow was on the ground.  Looks like spring to me.

Culinary Reminder

It was a crisp clear morning with birdless blue skies.  The migration has mostly drawn to a close; very little was seen despite a suitable northwest breeze to support a flight.   There were no robins and no blackbirds.  Not even a starling was seen today.  The only highlights were a Bufflehead (Bucephala albeola) and a couple of Swamp Sparrows.

A Swamp Sparrow is coaxed from the dense leafy cover of the Riverine Grasslands of Conewago Falls.
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And now ladies and gentlemen, boys and girls, it’s time for a Thanksgiving Day culinary reminder from the local Conewago Falls Turkey…

“That’s the Conewago Falls Turkey Vulture if you don’t mind.  And I’m here to remind you that this Thanksgiving, you don’t have to fight your way in there to get first pickings of the feast.  Take it from me, let those flavors and aromas intensify over time.  And juices, who needs juices?  Let that stuff congeal so everything sticks to your ribs.  Are you paying attention?  I’m telling you, just back off, let the crowd die down, then get in there and devour those leftovers.  They’re the best.  You’ll thank me later!”

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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State of Confusion

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.

The tiny Northern Spring Peeper is recognized by the dark “X” across its back.  Soon, shelter must be found among loose bark and fallen logs to commence hibernation.  Emergence, often prompted by warm spring rains, will quickly be followed by a growing chorus of breeding calls as sometimes hundreds of these frogs assemble in vernal pools where mating will then occur.

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.

Common Map Turtles, including this recently hatched young seen in August, are often observed climbing onto rocks in the river.
Note the oversize swimming fin adaptations of the feet on this adult Common Map Turtle found among the Pothole Rocks in Conewago Falls.  Young and adults are capable of navigating some strong current to feed and escape danger.
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SOURCES

Committee on the Status of Endangered Wildlife in Canada.  2002.  Status Report of the Northern Map Turtle.  Canadian Wildlife Service.  Ottawa, Ontario.

Summer Breeze

A moderate breeze from the south placed a headwind into the face of migrants trying to wing their way to winter quarters.  The urge to reach their destination overwhelmed any inclination a bird or insect may have had to stay put and try again another day.

Blue Jays were joined by increasing numbers of American Robins crossing the river in small groups to continue their migratory voyages.  Killdeer (Charadrius vociferous) and a handful of sandpipers headed down the river route.  Other migrants today included a Cooper’s Hawk (Accipiter cooperii), Eastern Bluebirds (Sialia sialis), and a few Common Mergansers (Mergus merganser), House Finches (Haemorhous mexicanus), and Common Grackles (Quiscalus quiscula).

The afternoon belonged to the insects.  The warm wind blew scores of Monarchs toward the north as they persistently flapped on a southwest heading.  Many may have actually lost ground today.  Painted Lady (Vanessa cardui) and Cloudless Sulphur butterflies were observed battling their way south as well.  All three of the common migrating dragonflies were seen: Common Green Darner (Anax junius), Wandering Glider (Pantala flavescens), and Black Saddlebags (Tramea lacerata).

The warm weather and summer breeze are expected to continue as the rain and wind from Hurricane Nate, today striking coastal Alabama and Mississippi, progresses toward the Susquehanna River watershed during the coming forty-eight hours.

This Great Blue Heron was joined by numerous other fishermen and a good number of sightseers in the falls today.
A colorful young Northern Water Snake (Nerodia sipedon) takes advantage of the sun-heated surface of a Pothole Rock to remain nimble and active.  Cooler weather will soon compel this and other reptiles to find shelter for winter hibernation.
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