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.

Photo of the Day

Birds of Conewago Falls in the Lower Susquehanna River Watershed: Red-necked Grebe
The Red-necked Grebe (Podiceps grisegena) is a rare but regular spring migrant in the Susquehanna valley.  After wintering along the coast, they journey to breeding locations on inland ponds in Canada and Alaska.  For the past several days, this one has been feeding on minnows along the river’s west shore just downstream of the mouth of the Conodoguinet Creek near Wormleysburg, Pennsylvania.

A Visit to Bombay Hook National Wildlife Refuge

It’s surprising how many millions of people travel the busy coastal routes of Delaware each year to leave the traffic congestion and hectic life of the northeast corridor behind to visit congested hectic shore towns like Rehobeth Beach, Bethany Beach, and Ocean City, Maryland.  They call it a vacation, or a holiday, or a weekend, and it’s exhausting.  What’s amazing is how many of them drive right by a breathtaking national treasure located along Delaware Bay just east of the city of Dover—and never know it.  A short detour on your route will take you there.  It’s Bombay Hook National Wildlife Refuge, a quiet but spectacular place that draws few crowds of tourists, but lots of birds and other wildlife.

Bombay Hook National Wildlife Refuge is located just off Route 9, a lightly-traveled coastal road east of Dover, Delaware.  Note the Big Bluestem and other warm season grasses in the background.  Bombay Hook, like other refuges in the system, is managed for the benefit of the wildlife that relies upon it to survive.  Within recent years, most of the mowed grass and tilled ground that once occurred here has been replaced by prairie grasses or successional growth, much to the delight of Northern Bobwhite (Colinus virginianus) and other species.

Let’s join Uncle Tyler Dyer and have a look around Bombay Hook.  He’s got his duck stamp and he’s ready to go.

Uncle Ty’s current United States Fish and Wildlife Service Duck Stamp displayed on his dashboard is free admission to the tour road at Bombay Hook and other National Wildlife Refuges.
The refuge at Bombay Hook includes woodlands, grasslands, and man-made freshwater impoundments, but it is largely comprised of thousands of acres of tidal salt marsh bordering and purifying the waters of Delaware Bay.  These marshes are renowned wintering areas for an Atlantic population of Snow Goose known as the “Greater Snow Goose” (Anser caerulescens atlanticus).  Thousands of these birds rising over the marsh into the glowing light of a setting sun is an unforgettable sight.
Trails at various stops along the auto tour route lead to observation towers and other features. This boardwalk meanders into the salt marsh grasses and includes a viewing area alongside a tidal creek.  Our visit coincided with a very high tide induced by east winds and a new moon.
During high tide, an Eastern Cottontail (Sylvilagus floridanus) seeks higher ground near the boardwalk and the wooded edge of the salt marsh.
As the tide rises, fast-flying shorebirds scramble from flooded mudflats in the salt marsh on the east side of the tour road.
When high tide arrives in the salt marshes, shorebirds and waterfowl often concentrate in the man-made freshwater pools on the west side of the tour road.  Glaring afternoon sun is not the best for viewing birds located west of the road.  For ideal light conditions, time your visit for a day when high tide occurs in the morning and recedes to low tide in the afternoon.
A view looking west into Shearness Pool, largest of the freshwater impoundments at Bombay Hook.
Bombay Hook has many secretive birds hiding in its wetlands, but they can often be located by the patient observer.  Here, two Pied-billed Grebes feed in an opening among the vegetation in a freshwater pool.
One of Bombay Hook’s resident Bald Eagles patrols the wetlands.
American Avocets (Recurvirostra americana) gather by the hundreds at Bombay Hook during the fall.  A passing eagle will stir them into flight.
An American Avocet, a delicate wader with a peculiar upturned bill.
As soon as the tide begins receding, shorebirds and waterfowl like these Green-winged Teal begin dispersing into the salt marshes to feed on the exposed mudflats.
The woodlands and forested areas of the refuge host resident songbirds and can be attractive to migrating species like this Yellow-rumped Warbler.
For much of its course, the tour road at Bombay Hook is located atop the dike that creates the man-made freshwater pools on the western edge of the tidal salt marsh.  If you drive slowly and make frequent stops to look and listen, you’ll notice an abundance of birds and other wildlife living along this border between two habitats.  Here, a Swamp Sparrow has a look around.
Savannah Sparrows are common along the tour road where native grasses grow wild.
Bombay Hook is renowned for its rarities. One of the attractions during the late summer and autumn of 2021 was a group of Roseate Spoonbills (Platalea ajaja), vagrants from the southern states, seen here with Great Egrets and Snowy Egrets (Egretta thula).
Roseate Spoonbills and Great Egrets at Bombay Hook.

Remember to go the Post Office and get your duck stamp.  You’ll be supporting habitat acquisition and improvements for the wildlife we cherish.  And if you get the chance, visit a National Wildlife Refuge.  November can be a great time to go, it’s bug-free!  Just take along your warmest clothing and plan to spend the day.  You won’t regret it.

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.

Get Away From It All

For those of you who dare to shed that filthy contaminated rag you’ve been told to breathe through so that you might instead get out and enjoy some clean air in a cherished place of solitude, here’s what’s around—go have a look.

Northern Flickers have arrived.  Look for them anywhere there are mature trees.  Despite the fact that flickers are woodpeckers, they often feed on the ground.  You’ll notice the white rump and yellow wing linings when they fly away.
The tiny Chipping Sparrow frequently nests in small trees in suburban gardens.  Lay off the lawn treatments to assure their success.
Field Sparrows (Spizella fusilla) are a breeding species in abandoned fields where successional growth is underway.
White-throated Sparrows spend the winter in the lower Susquehanna valley.  Their numbers are increasing now as waves of migrants pass through on their way north.
Northbound flocks of Rusty Blackbirds (Euphagus carolinus) are currently found feeding in forest swamps along the Susquehanna.  Their noisy calls sound like a chorus of squeaking hinges.
Migratory Red-shouldered Hawks are also making feeding stops at area wetlands.
The Palm Warbler (Setophaga palmarum) is easily identified by its tail pumping behavior.  Look for it in shrubs along the river shoreline or near lakes and streams.  Palm Warblers are among the earliest of the warblers to move through in the spring.

The springtime show on the water continues…

Common Loons will continue migrating through the area during the upcoming month.
Buffleheads are still transiting the watershed.
Horned Grebes are occurring on the river and on local lakes.
Seeing these one-year-old male Hooded Mergansers, the bachelors, wandering around without any adult males or females is a good sign.  The adults should have moved on to the breeding grounds and local pairs should be well into a nesting cycle by now.  Hatching could occur any day.
Like Hooded Mergansers, Wood Ducks are cavity nesters, but their egg laying, incubation, and hatching often occurs a month or more later than that of the hoodies.  Judging by the attentiveness of the drake, this pair of woodies is probably in the egg-laying stage of its breeding cycle right now.
Redheads (Aythya americana) are stopping for a rest on their way north.
In spring, Double-crested Cormorants proceed up the river in goose-like flocks with adult birds like these leading the way.

Hey, what are those showy flowers?

That’s Lesser Celandine (Ficaria verna).  It’s often called Fig Buttercup.  In early April it blankets stream banks throughout the lower Susquehanna region.  If you don’t remember seeing it growing like that when you were younger, there’s a reason.  Lesser Celandine is an escape from cultivation that has become invasive.  While the appearance is tolerable; it’s the palatability that ruins everything.  It’s poisonous if eaten by people or livestock.
The Eastern Spring Beauty (Claytonia virginica) is a dainty native wildflower of riparian forests and other woodlands throughout the lower Susquehanna valley.
The Trout Lily (Erythronium americanum) is beginning to bloom now.  It’s a native of the region’s damp forests.
Virginia Bluebells (Mertensia virginica) is not native to the Susquehanna watershed, but neither is it considered invasive.  It creates colorful patches in riparian forests.
Dutchman’s Breeches (Dicentra cucullaria) is a strikingly beautiful native wildflower that grows on undisturbed forested slopes throughout the Susquehanna valley.

Wasn’t that refreshing?  Now go take a walk.

The Fallout Continues

Fog and mist lingered throughout the day, as did the migratory water birds on the river and lakes in the lower Susquehanna valley.  As a continuation of yesterday’s post on the fallout, here’s a photo tour of some of the sites where ducks, loons, grebes, and other birds have gathered.

American Robins may have comprised a large portion of the northbound flight appearing on last evening’s radar images.  Today, hundreds could be seen on soggy lawns where earthworms might be found near the surface.  This flock was finding sustenance at Highspire’s Reservoir Park in Dauphin County.
This drake Gadwall (Mareca strepera) and two hens had dropped in for a visit at the Highspire Reservoir Park.
Hundreds of Buffleheads were on the fogged-in Susquehanna River at Harrisburg this afternoon.  From Front Street and Maclay Street in front of the Pennsylvania Governor’s Mansion, they seemed to be everywhere in sight on the rain-swollen current.  After passing downstream, flocks flew in a straight line formation just above the water’s surface as they made a short trip back up the river to then drift down through the channels once again.
A portion of a raft consisting of about three dozen Red-breasted Mergansers floats by the Pennsylvania Governor’s Mansion.  Several of the hundred or more Scaup on the river intermingled with these mergansers from time to time.
A lone Long-tailed Duck (Clanqula hyemalis) near the aforementioned raft of mergansers.  The Long-tailed Duck was formerly known as the Oldsquaw in North America.  The common name used in Britain and Europe is now preferred.
Two of at least a hundred Horned Grebes (Podiceps auritus) seen in the Susquehanna at Harrisburg this afternoon.
American Coots (Fulica americana) at Memorial Lake State Park in Lebanon County.
Buffleheads continue at Memorial Lake.
One more Common Loon than yesterday at Memorial Lake.
A mixed raft of diving ducks and grebes at Memorial Lake.
A closeup of the same raft reveals Buffleheads, Scaup, Ring-necked Ducks, Ruddy Ducks (Oxyura jamaicensis), a Pied-billed Grebe, and Horned Grebes.

Stormy weather certainly is a birder’s delight.

Fallout in the Lower Susquehanna River Watershed

Local birders enjoy going to the Atlantic coast of New Jersey and Delmarva in the winter.  The towns and beaches host far fewer people than birds, and many of the species seen are unlikely to be found anywhere else in the region.  Unusual rarities add to the excitement.

The regular seaside attraction in winter is the variety of diving ducks and similar water birds that feed in the ocean surf and in the saltwater bays.  Most of these birds breed in Canada and many stealthily cross over the landmass of the northeastern United States during their migrations.  If an inland birder wants to see these coastal specialties, a trip to the shore in winter or a much longer journey to Canada in the summer is normally necessary—unless there is a fallout.

Migrating birds can show up in strange places when a storm interrupts their flight.  Forest songbirds like thrushes and warblers frequently take temporary refuge in a wooded backyard or even in a city park when forced down by inclement weather.  Loons have been found in shopping center parking lots after mistaking the wet asphalt for a lake.  Fortunately though, loons, ducks, and other water birds usually find suitable ponds, lakes, and rivers as places of refuge when forced down.  For inland birders, a fallout like this can provide an opportunity to observe these coastal species close to home.

Not so coincidentally, it has rained throughout much of today in the Lower Susquehanna River Watershed, apparently interrupting a large movement of migrating birds.  There is, at the time of this writing, a significant fallout of coastal water birds here.  Hundreds of diving ducks and other benthic feeders are on the Susquehanna River and on some of the clearer lakes and ponds in the region.  They can be expected to remain until the storm passes and visibility improves—then they’ll promptly commence their exodus.

The following photographs were taken during today’s late afternoon thundershower at Memorial Lake State Park at Fort Indiantown Gap, Lebanon County.

A one-year-old male Hooded Merganser (Lophodytes cucullatus).
Red-breasted Mergansers (Mergus serrator) are a familiar sight in saltwater bays, not so familiar on inland bodies of water.
A small raft of Scaup (Aythya species).
A pair of Buffleheads.
A Common Loon that lands in a parking lot is unable to take flight again.  It must be transported to a body of water large enough for it to run across the surface and get the speed it needs to take off and resume its flight.  This Common Loon at Memorial Lake has selected an ideal fallout haven.  It will have plenty of runway space when it decides to leave.
A Pied-billed Grebe (Podilymbus podiceps) in a heavy downpour.

Migrating land birds have also been forced down by the persistent rains.

The tail-pumping Eastern Phoebe is a common sight around the lower Susquehanna valley right now.  Many will stay to breed, often building their nests under a man-made bridge, porch. or other structure.

Why not get out and take a slow quiet walk on a rainy day.  It may be the best time of all for viewing certain birds and other wildlife.

Wild Turkeys (Meleagris gallopovo) will often leave the cover of woodlands and forest to forage in the open during a rain shower.
During the final hours of this evening, wind-assisted flights of northbound migrating birds are indicated as blue masses around radar sites south of the Mason-Dixon Line.  These nocturnal flights may constitute yet another fallout in the area of the showers and storms shown passing west to east through Pennsylvania, adding to the existing concentration of grounded migrants in the lower Susquehanna valley.  (NOAA/National Weather Service image)