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!

Off To The Races

Trying to get a favorable place to nest before others arrive, the “early birds” are presently racing north through the lower Susquehanna valley.  Check out these sightings from earlier today…

Ring-necked Ducks
A pair of Ring-necked Ducks.
Hooded Mergansers
Hooded Mergansers, two males and a female.
American Wigeons
A pair of American Wigeons.
A male Canvasback.
A male Canvasback.
Eastern Phoebe
During these chilly days of late winter, this hardy Eastern Phoebe finds sustenance by seizing flying insects along the water’s edge.
An American Robin in classic worm-hunting posture.
Possibly our most familiar sign of spring, an American Robin in classic worm-hunting posture.
A Common Grackle in a maple tree that is starting to flower.
An iridescent Common Grackle in a maple tree that is beginning to flower.
A male Red-winged Blackbird singing near a small patch of cattails.
A male Red-winged Blackbird singing from a perch near a small patch of cattails.  During the spring migration, noisy flocks of males compete for a breeding territory at these sites.  Each of the victors defends his spot and awaits the arrival of a female mate while the losers move on to vie for their own breeding location farther north.

Time to get outside and have a look.  The spectacle of spring migration passes quickly.  You don’t want to miss it!

Migratory Waterfowl on Local Ponds and Lakes

Following the deep freeze of a week ago, temperatures soaring into the fifties and sixties during recent days have brought to mind thoughts of spring.  In the pond at susquehannawildlife.net headquarters, Green Frogs are again out and about.

Green Frogs
A pair of Green Frogs seen today alongside the headquarters pond.  A sign of spring?

But is this really an early spring?  Migrating waterfowl indicate otherwise.  Having been forced south from the Great Lakes during the bitter cold snap, a variety of our tardy web-footed friends belatedly arrived on the river and on the Susquehanna Flats of upper Chesapeake Bay about ten days ago.  Now, rising water from snow melt and this week’s rains have forced many of these ducks onto local lakes and ponds where ice coverage has been all but eliminated by the mild weather.  For the most part, these are lingering autumn migrants.  Here’s a sample of some of the waterfowl seen during a tour of the area today…

Snow Geese
Like other late-season migrants, Snow Geese take advantage of open water on area lakes until ice forces them south to the Atlantic Coastal Plain.  In a little more than a month from now, they’ll begin working their way north again.
Tundra Swans and American Black Ducks loafing on an ice-free lake.
Tundra Swans and American Black Ducks loafing on an ice-free lake.
Mute Swans
The non-native Mute Swan has become an invasive species.  Because they are predominantly non-migratory, groups of Mute Swans congregating in valuable wetland habitat can decimate these aquatic ecosystems with their persistent year-round feeding.  Their long necks help them consume enormous quantities of benthic foods that would otherwise be available to migratory diving ducks during their autumn and spring stopovers.
Gadwalls
Small flocks of Gadwalls will sometimes spend the winter on ice-free vegetated ponds in the lower Susquehanna region.
A mixed flock of diving ducks on a small lake.
A mixed flock of diving ducks on a small lake.  Let’s take a closer look!
Redheads, Lesser Scaup, and Canvasback
Six Redheads, three Lesser Scaup (top row left), and a Canvasback (upper right).
Redheads
Redheads.
Buffleheads
Buffleheads.
An adult male Lesser Scaup.
An adult male Lesser Scaup.
Lesser Scaup
A female (right) and a first-winter male (left) Lesser Scaup.
Canvasbacks and a Ruddy Duck
Canvasbacks and a Ruddy Duck.

With the worst of winter’s fury still to come, it’s time to say farewell to most of these travelers for a little while.  With a little luck, we’ll see them again in March or April.

Striped Skunk
Our official susquehannawildlife.net prognosticator climbed out of its winter hideout today to have a look around.   Then, without hesitation, the forecast for 2023 was issued, “Winter Stinks!”

2020: A Good Year

You say you really don’t want to take a look back at 2020?  Okay, we understand.  But here’s something you may find interesting, and it has to do with the Susquehanna River in 2020.

As you may know, the National Weather Service has calculated the mean temperature for the year 2020 as monitored just upriver from Conewago Falls at Harrisburg International Airport.  The 56.7° Fahrenheit value was the highest in nearly 130 years of monitoring at the various stations used to register official climate statistics for the capital city.  The previous high, 56.6°, was set in 1998.

Though not a prerequisite for its occurrence, record-breaking heat was accompanied by a drought in 2020.  Most of the Susquehanna River drainage basin experienced drought conditions during the second half of the year, particularly areas of the watershed upstream of Conewago Falls.  A lack of significant rainfall resulted in low river flows throughout late summer and much of the autumn.  Lacking water from the northern reaches, we see mid-river rocks and experience minimal readings on flow gauges along the lower Susquehanna, even if our local precipitation happens to be about average.

Back in October, when the river was about as low as it was going to get, we took a walk across the Susquehanna at Columbia-Wrightsville atop the Route 462/Veteran’s Memorial Bridge to have a look at the benthos—the life on the river’s bottom.

As we begin our stroll across the river, we quickly notice Mallards and a Double-crested Cormorant (far left) feeding among aquatic plants.  You can see the leaves of the vegetation just breaking the water’s surface, particularly behind the feeding waterfowl.  Let’s have a closer look.
An underwater meadow of American Eelgrass (Vallisneria americana) as seen from atop the Veteran’s Memorial Bridge at Columbia-Wrightsville.  Also known as Freshwater Eelgrass, Tapegrass, and Wild Celery, it is without a doubt the Susquehanna’s most important submerged aquatic plant.  It grows in alluvial substrate (gravel, sand, mud, etc.) in river segments with moderate to slow current.  Water three to six feet deep in bright sunshine is ideal for its growth, so an absence of flooding and the sun-blocking turbidity of muddy silt-laden water is favorable.
Plants in the genus Vallisneria have ribbon-like leaves up to three feet in length that grow from nodes rooted along the creeping stems called runners.  A single plant can, over a period of years, spread by runners to create a sizable clump or intertwine with other individual plants to establish dense meadows and an essential wildlife habitat.
An uprooted segment of eelgrass floats over a thick bed of what may be parts of the same plant.  Eelgrass meadows on the lower Susquehanna River were decimated by several events: deposition of anthracite coal sediments (culm) in the late-nineteenth and early-twentieth centuries, dredging of the same anthracite coal sediments during the mid-twentieth century, and the ongoing deposition of sediments from erosion occurring in farm fields, logged forests, abandoned mill ponds, and along denuded streambanks.  Not only has each of these events impacted the plants physically by either burying them or ripping them out by the roots, each has also contributed to the increase in water turbidity (cloudiness) that blocks sunlight and impairs their growth and recovery.
A submerged log surrounded by beds of eelgrass forms a haven for fishes in sections of the river lacking the structure found in rock-rich places like Conewago Falls.  A period absent of high water and sediment runoff extended through the growing season in 2020 to allow lush clumps of eelgrass like these to thrive and further improve water quality by taking up nutrients, particularly nitrogen and phosphorus.  Nutrients used by vascular plants including eelgrass become unavailable for feeding detrimental algal blooms in downstream waters including Chesapeake Bay.
Small fishes and invertebrates attract predatory fishes to eelgrass beds.  We watched this Smallmouth Bass leave an ambush site among eelgrass’s lush growth to shadow a Common Carp as it rummaged through the substrate for small bits of food.  The bass would snatch up crayfish that darted away from the cover of stones disturbed by the foraging carp.
Sunfishes are among the species taking advantage of eelgrass beds for spawning.  They’ll build a nest scrape in the margins between clumps of plants allowing their young quick access to dense cover upon hatching.  The abundance of invertebrate life among the leaves of eelgrass nourishes feeding fishes, and in turn provides food for predators including Bald Eagles, this one carrying a freshly-caught Bluegill.

These improvements in water quality and wildlife habitat can have a ripple effect.  In 2020, the reduction in nutrient loads entering Chesapeake Bay from the low-flowing Susquehanna may have combined with better-than-average flows from some of the bay’s lesser-polluted smaller tributaries to yield a reduction in the size of the bay’s oxygen-deprived “dead zones”.  These dead zones typically occur in late summer when water temperatures are at their warmest, dissolved oxygen levels are at their lowest, and nutrient-fed algal blooms have peaked and died.  Algal blooms can self-enhance their severity by clouding water, which blocks sunlight from reaching submerged aquatic plants and stunts their growth—making quantities of unconsumed nutrients available to make more algae.  When a huge biomass of algae dies in a susceptible part of the bay, its decay can consume enough of the remaining dissolved oxygen to kill aquatic organisms and create a “dead zone”.  The Chesapeake Bay Program reports that the average size of this year’s dead zone was 1.0 cubic miles, just below the 35-year average of 1.2 cubic miles.

Back on a stormy day in mid-November, 2020, we took a look at the tidal freshwater section of Chesapeake Bay, the area known as Susquehanna Flats, located just to the southwest of the river’s mouth at Havre de Grace, Maryland.  We wanted to see how the restored American Eelgrass beds there might have fared during a growing season with below average loads of nutrients and life-choking sediments spilling out of the nearby Susquehanna River.  Here’s what we saw.

We followed the signs from Havre de Grace to Swan Harbor Farm Park.
Harford County Parks and Recreation’s Swan Harbor Farm Park consists of a recently-acquired farming estate overlooking the tidal freshwater of Susquehanna Flats.
Along the bay shore, a gazebo and a fishing pier have been added.  Both provide excellent observation points.
The shoreline looked the way it should look on upper Chesapeake Bay, a vegetated buffer and piles of trees and other organic matter at the high-water line.  There was less man-made garbage than we might find following a summer that experienced an outflow from river flooding, but there was still more than we should be seeing.
Judging by the piles of fresh American Eelgrass on the beach, it looks like it’s been a good year.  Though considered a freshwater plant, eelgrass will tolerate some brackish water, which typically invades upper Chesapeake Bay each autumn due to a seasonal reduction in freshwater inflow from the Susquehanna and other tributaries.  Saltwater can creep still further north when the freshwater input falls below seasonal norms during years of severe drought.  The Susquehanna Flats portion of the upper bay very rarely experiences an invasion by brackish water; there was none in 2020.
As we scanned the area with binoculars and a spotting scope, a raft of over one thousand ducks and American Coots (foreground) could be seen bobbing among floating eelgrass leaves and clumps of the plants that had broken away from their mooring in the mud.  Waterfowl feed on eelgrass leaves and on the isopods and other invertebrates that make this plant community their home.
While coots and grebes seemed to favor the shallower water near shore, a wide variety of both diving and dabbling ducks were widespread in the eelgrass beds more distant.  Discernable were Ring-necked Ducks, scaup, scoters, Long-tailed Ducks, Redheads, American Wigeons, Gadwall, Ruddy Ducks, American Black Ducks, and Buffleheads.

We noticed a few Canvasbacks (Aythya valisineria) on the Susquehanna Flats during our visit.  Canvasbacks are renowned as benthic feeders, preferring the tubers and other parts of submerged aquatic plants (a.k.a. submersed aquatic vegetation or S.A.V.) including eelgrass, but also feeding on invertebrates including bivalves.  The association between Canvasbacks and eelgrass is reflected in the former’s scientific species name valisineria, a derivitive of the genus name of the latter, Vallisneria.

Canvasbacks on Chesapeake Bay.  (United States Fish and Wildlife Service image by Ryan Hagerty)

The plight of the Canvasback and of American Eelgrass on the Susquehanna River was described by Herbert H. Beck in his account of the birds found in Lancaster County, Pennsylvania, published in 1924:

“Like all ducks, however, it stops to feed within the county less frequently than formerly, principally because the vast beds of wild celery which existed earlier on broads of the Susquehanna, as at Marietta and Washington Borough, have now been almost entirely wiped out by sedimentation of culm (anthracite coal waste).  Prior to 1875 the four or five square miles of quiet water off Marietta were often as abundantly spread with wild fowl as the Susquehanna Flats are now.”

Beck quotes old Marietta resident and gunner Henry Zink:

“Sometimes there were as many as 500,000 ducks of various kinds on the Marietta broad at one time.”

The abundance of Canvasbacks and other ducks on the Susquehanna Flats would eventually plummet too.  In the 1950s, there were an estimated 250, 000 Canvasbacks wintering on Chesapeake Bay, primarily in the area of the American Eelgrass, a.k.a. Wild Celery, beds on the Susquehanna Flats.  When those eelgrass beds started disappearing during the second half of the twentieth century, the numbers of Canvasbacks wintering on the bay took a nosedive.  As a population, the birds moved elsewhere to feed on different sources of food, often in saltier estuarine waters.

Canvasbacks were able to eat other foods and change their winter range to adapt to the loss of habitat on the Susquehanna River and Chesapeake Bay.  But not all species are the omnivores that Canvasbacks happen to be, so they can’t just change their diet and/or fly away to a better place.  And every time a habitat like the American Eelgrass plant community is eliminated from a region, it fragments the range for each species that relied upon it for all or part of its life cycle.  Wildlife species get compacted into smaller and smaller suitable spaces and eventually their abundance and diversity are impacted.  We sometimes marvel at large concentrations of birds and other wildlife without seeing the whole picture—that man has compressed them into ever-shrinking pieces of habitat that are but a fraction of the widespread environs they once utilized for survival.  Then we sometimes harass and persecute them on the little pieces of refuge that remain.  It’s not very nice, is it?

By the end of 2020, things on the Susquehanna were getting back to normal.  Near normal rainfall over much of the watershed during the final three months of the year was supplemented by a mid-December snowstorm, then heavy downpours on Christmas Eve melted it all away.  Several days later, the Susquehanna River was bank full and dishing out some minor flooding for the first time since early May.  Isn’t it great to get back to normal?

The rain-and-snow-melt-swollen Susquehanna from Chickies Rock looking upriver toward Marietta during the high-water crest on December 27th.
Cresting at Columbia as seen from the Route 462/Veteran’s Memorial Bridge.  A Great Black-backed Gull monitors the waters for edibles.
All back to normal on the Susquehanna to end 2020.
Yep, back to normal on the Susquehanna.  Maybe 2021 will turn out to be another good year, or maybe it’ll  just be a Michelin or Firestone.

SOURCES

Beck, Herbert H.  1924.  A Chapter on the Ornithology of Lancaster County, Pennsylvania.  The Lewis Historical Publishing Company.  New York, NY.

White, Christopher P.  1989.  Chesapeake Bay, Nature of the Estuary: A Field Guide.  Tidewater Publishers.  Centreville, MD.

Piles of Green Tape

A couple of inches of rain this week caused a small increase in the flow of the river, just a burp, nothing major.  This higher water coincided with some breezy days that kicked up some chop on the open waters of the Susquehanna upstream of Conewago Falls.  Apparently it was just enough turbulence to uproot some aquatic plants and send them floating into the falls.

Piled against and upon the upstream side of many of the Pothole Rocks were thousands of two to three feet-long flat ribbon-like opaque green leaves of Tapegrass, also called Wild Celery, but better known as American Eelgrass (Vallisneria americana).  Some leaves were still attached to a short set of clustered roots.  It appears that most of the plants broke free from creeping rootstock along the edge of one of this species’ spreading masses which happened to thrive during the second half of the summer.  You’ll recall that persistent high water through much of the growing season kept aquatic plants beneath a blanket of muddy current.  The American Eelgrass colonies from which these specimens originated must have grown vigorously during the favorable conditions in the month of August.  A few plants bore the long thread-like pistillate flower stems with a fruit cluster still intact.  During the recent few weeks, there have been mats of American Eelgrass visible, the tops of their leaves floating on the shallow river surface, near the east and west shorelines of the Susquehanna where it begins its pass through the Gettysburg Basin near the Pennsylvania Turnpike bridge at Highspire.  This location is a probable source of the plants found in the falls today.

Uprooted American Eelgrass floating into the Pothole Rocks under the power of a north wind.  Note the white thread-like pistillate flower stem to the left and the small rooted specimen to the upper right.  The latter is likely a plant from the creeping rootstock on the edge of a colony.  As a native aquatic species, American Eelgrass is a critical link in the Susquehanna River and Chesapeake Bay food chain.  Its decimation by pollution during the twentieth century led to migration pattern alterations and severe population losses for the Canvasback (Aythya valisineria) duck.
American Eelgrass, a very small specimen, found growing in a low-lying Pothole Rock alongside the accumulations of freshly arriving material from upstream.  Note that the creeping rootstock has leaves growing from at least three nodes on this plant.  Eelgrass dislocations are regular occurrences which sometimes begin new colonies, like the small one seen here in this Diabase Pothole Rock Microhabitat.

The cool breeze from the north was a perfect fit for today’s migration count.  Nocturnal migrants settling down for the day in the Riparian Woodlands at sunrise included more than a dozen warblers and some Gray Catbirds (Dumetella carolinensis).  Diurnal migration was underway shortly thereafter.

A moderate flight of nocturnal migrants is indicated around NEXRAD sites in the northeastern states at 3:18 AM EDT.  The outer rain bands of Hurricane Irma can be seen approaching the Florida Keys as the storm closes in on the peninsula.  (NOAA/National Weather Service image)

Four Bald Eagles were counted as migrants this morning.  Based on plumage, two were first-year eagles (Juvenile) seen up high and flying the river downstream, one was a second-year bird (Basic I) with a jagged-looking wing molt, and a third was probably a fourth year (Basic III) eagle looking much like an adult with the exception of a black terminal band on the tail.  These birds were the only ones which could safely be differentiated from the seven or more Bald Eagles of varying ages found within the past few weeks to be lingering at Conewago Falls.  There were as many as a dozen eagles which appeared to be moving through the falls area that may have been migrating, but the four counted were the only ones readily separable from the locals.

Red-tailed Hawks (Buteo jamaicensis) were observed riding the wind to journey not on a course following the river, but flying across it and riding the updraft on the York Haven Diabase ridge from northeast to southwest.

Bank Swallows (Riparia riparia) seem to have moved on.  None were discovered among the swarms of other species today.

Ruby-throated Hummingbirds, Caspian Terns, Cedar Waxwings (Bombycilla cedrorum), and Chimney Swifts (Chaetura pelagica) were migrating today, as were Monarch butterflies.

Not migrating, but always fun to have around, all four wise guys were here today.  I’m referring to the four members of the Corvid family regularly found in the Mid-Atlantic states: Blue Jay (Cyanocitta cristata), American Crow (Corvus brachyrhynchos), Fish Crow (Corvus ossifragus), and Common Raven (Corvus corax).

It looks like a big Blue Jay, but it’s not.  This Belted Kingfisher (Megaceryle alcyon) takes a break after flying around the falls trying to shake a marauding Ruby-throated Hummingbird off its tail.
CLICK ON THE LOGO FOR TODAY’S MIGRATION COUNT TOTALS

SOURCES

Klots, Elsie B.  1966.  The New Field Book of Freshwater Life.  G. P. Putnam’s Sons.  New York, NY.