Migrating Waterfowl on Lotic Fresh Waters

Lotic vs. Lentic Freshwater Ecosystems — Some comparative attributes of unspoiled lotic vs. lentic freshwater ecosystems. Low-gradient (slow-moving) lotic waters often create, and remain connected to, accompanying riverine wetlands (a lentic freshwater ecosystem). These swamps, marshes, and ditches absorb, purify, and infiltrate flood waters while supporting a diverse number of plant and animal species.

We frequently perceive all waterfowl migration to be synchronized with the conspicuous movements of familiar species like Snow Geese, Tundra Swans, and Canada Geese—big flights coming south in October and November, then a return to the north in late February and March. And we’re all quite aware of the occurrence of large gatherings of some of these migrants while they make stopovers on some of our largest lentic (still) waters—the man-made lakes and reservoirs created by damming local streams. But did you know that there are populations of colorful waterfowl with dynamic migrations that extend throughout the winter and early spring with movements that are often continuous. Under favorable conditions, these birds favor the lotic (flowing) waters of the river and its larger tributaries as they transit the lower Susquehanna valley. That’s because unpolluted lotic freshwater ecosystems support a greater diversity of plants and animals than lentic waters, and therefore offer more opportunities for hungry migrating waterfowl to find food. Let’s have a look at some of the species that visit the river during their seasonal journeys…

Ice on the Susquehanna — While the urge to head south in the autumn is largely stimulated by the shortening of the photoperiod, it is the presence of ice, particularly on glacial lakes throughout the lands to the north of the lower Susquehanna River basin, that pushes many diving ducks to finally make their way south toward the guarantee of open-water feeding areas along the coast. This movement may occur at anytime between November and late February or, as we have seen during some of the mild winters of recent decades, it may scarcely be noticed at all.

Common Mergansers often lead they way when it comes to migratory diving ducks. They regularly move south in conspicuous numbers by late November and December and are regularly pushing north as soon as the ice begins to melt. During a typical year, it is not unusual for some populations of these large diving birds to remain north of us during the winter. Then, in the days after a sudden rush of frigid polar air, an appreciable increase in ice cover will force a mid-winter movement of birds down the Susquehanna.

Heat Flux Sources Impacting Temperature in Lotic Fresh Waters — Temperatures in lotic fresh waters vary over the length of the stream or river. They are largely determined by the collective impact of the numerous sources of heat flux depicted in this graphic. (Environmental Protection Agency image)

Buffleheads begin passing through the lower Susquehanna region in Novemeber on their way to coastal saltwater bays for the winter. Lingering populations feed by diving in the river’s pools and riffles for benthic invertebrates including snails and insect larvae. Lesser quantities of aquatic plant matter supplement their diet.

Many Common Goldeneyes will remain on shallow, ice-free waters of the northern lakes and rivers sculpted by the most recent glacial event, but only until they are forced south into and through the lower Susquehanna valley by the encroachment of freezing conditions. On the river, they are among the dozen or so species of diving ducks we see visiting or passing through during the typical late fall and early river.

Geomorphological Zonation of a Stream or River — During their visits to the lotic (also known as riverine) fresh waters of the Susquehanna and its largest tributaries, benthic-feeding waterfowl make short dives to take advantage of the plants, small fish, invertebrates, and other food sources inhabiting the stream bottom in the riffles and pools of the free-flowing waterway. Substrates, listed here by size (in descending order), along with other parameters influenced by this zonation determine the variety and abundance of the forage available to migrating waterfowl and other consumers. Ice or high water and poor visibility due to flooding can render the riffles and pools of the channel unusable for feeding. The birds then must choose to either linger and rest without feeding or leave the lotic freshwater habitat to seek sustenance. During a flood, this may require relocation to a nearby lentic (still) body of fresh water such as a lake or reservoir. The presence of ice will almost invariably force the birds to fly on to the Atlantic Coastal Plain and the tidal waters of its bays and estuaries.

Hooded Mergansers are one of the few species of diving ducks likely to utilize flooded shoreline timber and riverine (fluvial) wetlands as refuge from high water on Susquehanna.

Pied-billed Grebe and Canvasbacks — A Pied-billed Grebe and a pair of Canvasbacks on an ice-free stretch of the lower Susquehanna in mid-winter feed and loaf in a riffle-flanked pool where a large mat of American Eelgrass, a submerged aquatic plant also known as Tapegrass or Wild Celery, grows during the summer. The complex layout of riffles and pools in a river this size offers tremendous opportunities for a diverse array a species to find their niche wherein they can survive and flourish.

The presence of ice forces Buffleheads and other diving ducks to gather in turbulent open water, often below a riffle or dam. Another alternative is to continue on toward the salty bays and estuaries of the coast. High water may push these birds into the shallows among the flooded woods to feed, but they seldom utilize heavily forested riparian wetlands as a refuge due to their need for a running start to get airborne.

**Riffle and Pool Characteristics of High Gradient (A) and Low Gradient (B) Streams**. This graphic illustrates the change in deposition characteristics of a stream or river as its gradient decreases. A high-gradient stream (A) has a rapid velocity, often forms falls, and tends to carry away a high volume of all but the largest of particles of potential substrates as they erode from the surrounding landscape. On a low-gradient stream, the loss in water velocity reduces the water column’s ability to transport even the smallest of substrate particles. Deposition of this gravel, sand, silt, and clay forms lateral bars that over time create the familiar meandering path of a naturally flowing lowland stream. (National Park Service image)

Benthic Life in Lotic Freshwaters — Benthic substrates in lotic freshwater pools and riffles support an abundance of life forms ranging from colorful diatoms on rocks and cobble, to invertebrates including snails and insect larvae, to fishes like this young Channel Catfish. Free of accumulations of sediment, this river bottom not only provides habitat for a healthy fishery, it facilitates the bidirectional exchange of water between the Susquehanna and its underlying aquifer.

On the lower Susquehanna, populations of young Quillback suckers are found almost exclusively in clear, high-gradient pools.

The Harlequin Duck winters along the rocky shores and man-made jetties of the Atlantic coast. In summer, they nest on fast-moving, headwater streams well to our north. Very rare on the Susquehanna, this is the first of two individuals found during March and April of 2025. It was observed feeding in the swift waters of the high-gradient riffles and pools where the river cuts through Blue Mountain north of Harrisburg. During previous weeks, Harlequin Ducks were being seen along the coast as far south as the mouth of the Chesapeake at Cape Charles, Virginia. It’s very possible that some of these birds traveled north through the bay area and up the Susquehanna on their way north.

**Fluvial Geomorphology of a Stream**. Many of the Susquehanna’s tributaries pass through each of these three erosional zones. Along the way, they carry out the process of breaking down the mountains formed by the Allegheny orogeny, the collision of North America and Africa that created the supercontinent Pangea about 325 to 260 million years ago (during portions of both the Carboniferous and Permian periods). Today’s main stem of the lower Susquehanna passes through a transfer zone (Zone 2), carrying eroded materials to a depositional zone (Zone 3) located within the ancient Susquehanna canyon stretching from Havre de Grace, Maryland, to Norfolk Canyon on the edge of the continental shelf. Within this zone, more than a 10,000-year accumulation of post-glacial sediments lies submerged by the rising waters of the Atlantic Ocean and Chesapeake Bay. Although the present-day lower Susquehanna is largely a transfer zone, some deposition occurs along low-gradient segments of the river, particularly where its course parallels the watershed’s ridges both above and below the high-gradient rapids where its path has eroded passage through the highlands. (National Park Service image)

Although the present-day lower Susquehanna is largely a transfer zone, some deposition occurs along low-gradient segments of the river, particularly where its course parallels the watershed’s ridges both above and below the high-gradient rapids where its path continues to erode passage through the bedrock. On this 1908 map of the Susquehanna at Conewago Falls, alluvial terraces of gravel, sand, silt, and clay can readily been seen as pale areas nearly lacking brown contour lines along the shorelines and islands of the river. Deposits within most of these terraces date back to the melt period following the most recent glacial event and beyond. The delta shown at the mouth of Conewago Creek (west) includes massive volumes of material deposited by both the creek and the river. This delta is currently known as Brunner Island, much of it developed as the site of a coal/gas-fired electric generating station. Terrace deposits along the Susquehanna’s shorelines created extensive perched marshes and swamps (wooded marshes) fed by rains, high river water, small streams, and springs, the latter often seeping from the base of the rocky escarpments carved by the ancient Susquehanna and defining the present-day inland border of the floodplain. We call these sites “Alluvial Terrace Wetlands”. Few of these critical components of river morphology survive. Those not drained for farmland were obliterated by urbanization and canal, railroad, and highway construction. (United States Geological Survey base image: Middletown, PA, quadrangle, 1908)

Water Willow is a familiar emergent plant that colonizes lateral bars and other alluvial deposits in low-gradient segments of the Susquehanna.

Water Willow Roots — The fine roots of Water Willow collect sediment and absorb nutrients while creating dense cover for young fish and numerous species of invertebrates including the Virginian River Horn Snails seen here.

Prior to the nineteenth century, the low-gradient flow regime of the river both above and below the riffles at Chiques Rock (lower right on map) created prime wildlife habitat. The natural accumulations of nutrients and substrates carried into and through the lotic waterway’s pools and riffles were cycled into an ideal growing medium for extensive mats of American Eelgrass and other aquatic plants. This underwater forest hosted a seemingly endless abundance of invertebrates and fishes (both resident and migratory)—supporting a variety of consumer species including various populations of humans. But soon after the mass clearing of much of the watershed’s land for farming and lumber, the mill ponds created by dams constructed on streams to power saw and grain mills became brimful with sediments eroded from the unprotected ground. During storm events, torrents of these sediments then flowed full bore toward the Susquehanna, and began accumulating in the low-gradient segments of the river.

Legacy Sediments — Sediments left behind after the removal of mill dams are known as legacy sediments. They disconnect the stream from its historic floodplain and riverine wetlands, thus intensifying the impact of high water in the surrounding landscape. As these nutrient-charged deposits wash away, they become a source of pollution in the waters of the Susquehanna and Chesapeake.

A mat of American Eelgrass growing in the flowing waters of the Susquehanna below Conewago Falls. Eelgrass and other submerged aquatic plants consume nutrients deposited in the cobble, gravel, and sand substrate of the river’s pools. Excess quantities of smaller particles of silt and clay can clog the substrate and thus inhibit the hyporheic exchange of water between the stream channel and the underlying aquifer, often diminishing the biomass and diversity of organisms inhabiting this benthic habitat. Buried in these life-choking sediments, the river bottom becomes inhospitable to growth of submerged aquatics including eelgrass.

This low-gradient stretch of the Susquehanna at Marietta flows parallel to the Chickies Quartzite “Hellam Hills” before making a sharp right turn to punch through the ridge as a series of rapids. Formerly a fully functional lotic ecosystem and a paradise for migrating waterfowl, this river segment is now impaired by accumulations of nutrient-laden sediments from agricultural and urban runoff.

Conewago Falls Flood Waters — Nutrient and sediment-loaded flood waters roar over the York Haven Dam and Conewago Falls…

Flood Waters at Haldeman Riffles — …past Brunner Island (left power plant stacks) and through Haldeman Riffles and the Shocks Railroad Bridge…

Flooding on the Marietta Broads — …into the stretch of river along the base of the “Hellam Hills” known as the “Marietta broads”. The low stream gradient here produces a slower current and increased deposition of sediments.

Redheads, Canvasbacks, and a Horned Grebe — Anytime from November to April on the lower Susquehanna, a group of Redheads, Canvasbacks (3 birds to right of the middle of the picture), and a Horned Grebe (lower left) is a welcome sight in a riverine pool known to have a summertime growth of American Eelgrass. Noted Dr. Herbert Beck in 1924 when describing the Canvasback, “Like all ducks, …, it stops to feed within the county (Lancaster) 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. 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. Sometimes there were as many as 500,000 ducks of various kinds on the Marietta broad at one time.”

Aythya genus ducks. — Today, seeing just dozens of Aythya genus ducks (Redheads, Canvasbacks, scaup) on the lower Susquehanna is a notable event. If they happen to be forced down by inclement weather while migrating through, you might get lucky enough to see several hundred.

During the past two centuries, as food supplies in the Susquehanna grew increasingly compromised for benthic feeders like these Lesser Scaup and other diving ducks, a change in distribution was necessary for survival.

Lesser Scaup in flight. — As individual species, Lesser Scaup and other waterfowl that fail to adapt to natural or man-made changes in their habitats and food supplies may see their overall global numbers falter.

Despite being located in the transfer zone, the lower Susquehanna has become a significant depositional zone along much of its length, mostly courtesy of the placement of sediment-trapping man-made dams.

Following construction of the mill dams and ponds on nearly every mile of the lower Susquehanna’s low-gradient tributary streams, enterprising parties moved on to the river. The first significant spans were constructed using wide timber cribs filled with large rock. They were placed to create water deep enough to allow canal boats to cross the Susquehanna at both Clark’s Ferry at the mouth of the Juniata River in Dauphin County and at Columbia/Wrightsville. These dams also diverted water into the newly excavated canals: the Pennsylvania Eastern Division Canal (completed in 1833) which followed the river’s east shore from Clark’s Ferry to Columbia, and the Susquehanna and Tidewater Canal (completed in 1840) along the west shore from Wrightsville to Havre de Grace, Maryland. Placement of these sediment-trapping man-made dams began a process of converting vast mileage of the lower Susquehanna from a transfer zone into a deposition zone. In addition, layout of the canals and locks followed the contours along the base of the riverside ridges, seriously altering most of the alluvial terrace wetlands that the river had created as a feature of its floodplain during the post-glacial period.

Construction of the canal dams was just the beginning. During the twentieth century, more massive dams would be added to the main stem of the river for hydroelectric energy production at York Haven, Safe Harbor, Holtwood, and Conowingo. Upon their completion, the days of unassisted anadromous fish migrations were over. On the river and its tributaries, smaller low-head dams maintain water levels for boating and recreation, but still function as current diminishing pseudo-lentic waters that blanket the lotic riffle and pool substrates with polluted sediments.

MAN-MADE DAMS TURN LOTIC WATERS INTO UNFLUSHED TOILETS

Sediment Deposition Behind Lower Susquehanna Dams — The construction of dams on the lower Susquehanna has converted vast mileage of the river from a lotic freshwater system into a series of man-made lentic freshwater lakes. These areas have lost their function as a lotic transfer zone and are now a sort of dysfunctional series of depositional zones collecting vast volumes of sediment containing nutrients and other pollutants. Within each impoundment, the reduced velocity of the river causes it to drop suspended sand first, then the finer particles of silt and clay closer to the dam. The flow regime of riffles and pools is lost and the hyporheic zone that exchanges water between the river and the underlying aquifer is clogged. These impaired segments of river become ripe for eutrophication: algal blooms followed by die offs that can lead to a fatal reduction of dissolved oxygen in the water column.

Deposits of lateral bars of sediment in low-gradient segments of the Susquehanna can create shallow water feeding habitat for puddle/dabbling ducks like these Gadwall. Where sediment pollution is severe, benthic foods in these areas often consist mostly of invertebrates and plant matter deposited by the current, the buried substrates devoid of a functioning ecosystem and the waters subject to eutrophication.

Common Goldeneyes on a patch of open water on an otherwise ice-covered “Lake Clark”, the impoundment created by Safe Harbor Dam. While they may find this spot advantageous for loafing, the food supply over the sediment-layered substrate will be limited.

By the end of the twentieth century, accumulations of polluted sediments behind lower Susquehanna dams were nearing capacity. There is no working plan to attenuate the massive release of these pollutants that may be triggered by a catastrophic flood. The effort to reduce nutrient and sediment runoff remains the focus so that new loading is kept to a minimum and won’t add to the capacity problems at the dams, nor will it continue on to the Chesapeake at full strength when the dams are full. Alleviating the sediment aggregation problem within the river’s impoundments is tall order and a dilemma not easily solved. (United States Geological Survey image)

Fortunately for everything else living in the benthos, Common Mergansers are big enough to devour invasive Rusty Crayfish when they find them in our lotic waterways.

TIME TO CLEAN UP OUR ACT

WHERE DOES YOUR STORMWATER GO?

Channelized Urban Stream — Nutrient and sediment loads from urban runoff and impaired creeks accumulate in low-gradient segments of the Susquehanna. Aggressively working to implement projects that eliminate these non-point sources of pollution are the only effective way to keep the problem from getting worse. Making things better requires a lot more effort. (United States Geological Survey image by Frank Ippolito)

RIPARIAN BUFFERS MAKE A DIFFERENCE…WIDER IS BETTER

FLOODPLAIN RESTORATION

Floodplain and Stream Restoration — This legacy sediment removal project restored the same creek to a braided meandering path while also reconnecting it to its historic floodplain. In just their second year, the wetlands are effectively absorbing stormwater and sequestering nutrients as an attached component of the riffle and pool complex. During our visit earlier this week, we found American Toads, Northern Leopard Frogs (Lithobates pipiens), and Northern Spring Peepers breeding there!

“STOP HEMMING AND HAWING AROUND ALREADY”

“HEY COWBOY, HOW ‘BOUT GETTIN’ THEM FILTHY LITTLE DOGIES OUTTA DAT CRICK?”

Impaired Stream — Here’s a polluted pasture stream with grazing livestock defecating where access to water is gained at a broken down embankment of nutrient-loaded legacy sediments left behind at an abandoned mill pond site. It’s a reminder that all it takes is just one stubborn jackass to foul up the whole waterway.

“ATTABOY TEX, THAT’S MORE LIKE IT!”

Stream Fencing and Livestock Crossing — Now that’s better. Legacy sediments have been removed to reconnect the stream to its floodplain. A livestock crossing and exclusion fencing has been installed, and a nutrient-consuming riparian buffer has been planted. This stream segment’s pollution woes have been mitigated.

AND FINALLY,…

…WHEN IT COMES TO BUILDING DAMS ON LOTIC FRESHWATERS—…

Sandhill Cranes in Beaver Pond — …Leave it to Beavers, they know how it’s done.

COMING SOON…

Horned Grebes are regular migrants and sometimes winter residents on ice-free stretches of the lower Susquehanna. They spend their time plying the benthic substrate of the river’s clear riffles and pools for a variety of invertebrates and small fish. Look for them moving north in coming days sporting this beautiful breeding plumage.

April and early May are prime time for observing Common Loons on the Susquehanna as they undertake a journey from the Atlantic surf where they spent the winter to nesting sites on northern lakes. For this migrant in breeding plumage, clear water for sighting plenty of benthic life in the river’s riffles and pools assures a successful dive in search of energy-replenishing forage.

March 23, 2026

Photo of the Day

With southerly breezes to push them along, insectivorous songbirds are beginning to arrive throughout the lower Susquehanna valley. By the first week of March, Tree Swallows started their push up the river corridor, relying upon the late-winter hatches of stoneflies and other cold-hardy flying insects for sustenance. As temperatures warmed during mid-month, greater numbers of these colorful cavity nesters ventured out across upland areas in search of suitable breeding sites in grasslands and pastures near water. Upon finding a good home in a dead tree or nest box, they’ll defend it vigorously to discourage encroachment.

March 15, 2026March 15, 2026

The Next Wave

Our first big wave of northbound migrants has come and gone, but don’t despair; for spring is still a few days away, and we have yet to reach the end of the beginning …

Migrating Canada Geese — All but the last of the migratory Canada Geese have passed through the lower Susquehanna basin en route to their nesting grounds in the land for which they are named. Those that remain are mostly members of a resident population established here during the latter decades of the twentieth century.

Migrating Tundra Swans — The majority of the northwest-flying Tundra Swans that wintered on the Atlantic Coastal Plain and will nest in Alaska and western Canada have now traversed our skies and are on their way through the Eastern Great Lakes region.

Snow Goose — Snow Geese too have departed. Only stragglers like this individual with a wounded wing linger.

Migrating Ring-billed Gulls — Still moving up the river corridor are thousands of Ring-billed Gulls. Their movements are prolonged, extending through much of the late winter and into early spring with primarily adult birds leading the way.

The Red-winged Blackbird exodus continues as well with mostly male birds like this one venturing on ahead of the females to secure suitable breeding sites before the arrival of the competition.

Displaying Common Grackle — Male Common Grackles are coming north to lay claim to favorable nesting habitat too. In an effort to fend off rivals, a male will thrust back his head and ruffle his feathers to display the colorful sheen adorning his plumage.

Recognized by their nasal two-syllable calls, Fish Crows have been filtering up the valleys of the river’s main stem and its tributaries for almost a month now. While the closely related American Crow is numerous throughout the winter in the lower Susquehanna watershed, most of our Fish Crows retreat to the Atlantic Coastal Plain during the colder months.

The Fish Crows that return early stake claims on the best nest sites, often in lowland areas where they are sometimes in direct competition with a portion of the population of American Crows that commonly breeds here.

With the arrival of the spring equinox, longer periods of daylight will accompany the return of many more species. Be sure to get outside, then have a look around.

March 8, 2026March 8, 2026

Look, Up in the Sky, It’s a Bird, No, Wait, It’s a Bunch of Birds!

Step outside, take a listen, and look up. A substantial northward movement of early migrants is, at this writing, underway across the lower Susquehanna basin—primarily in the skies within five to maybe ten miles of the river corridor. Within the last hour, we witnessed a steady parade of geese, swans, and blackbirds in the skies above the headquarters garden. These are not birds that are staging or are in the midst of a stopover here during their journey north. They are instead flocks taking advantage of favorable conditions to make a big jump from Chesapeake Bay and adjacent areas of the Atlantic Coastal Plain into territory to our north and northwest that was just two weeks ago in the middle of a deep freeze. Compared to the slowpokes whose northbound movements are a bit more cautious, the shared determination of these birds to get to the nesting grounds first may be advantageous for their breeding success.

Canada Geese and Blackbirds — Below them, flocks of hundreds of blackbirds including these Common Grackles and Red-winged Blackbirds filtered through.

Tundra Swans — …because they’re gone in just moments for another year.

Winds from the southwest are forecast for the coming couple of days, so the movements could continue. Head outside, enjoy the weather, and look up.

March 2, 2026March 6, 2026

Do Chipmunks Really Eat All That Food They Stash Away in the Fall?

Eastern Chipmunks are familiar mammals of our deciduous forests and wooded neighborhoods. They are surprisingly solitary and territorial, defending their well-concealed underground excavations vigorously to protect them from would-be intruders—including other chipmunks. Their individual effort to stockpile a cache of seeds, nuts, and other non-perishable foods during the autumn will largely determine whether or not they survive winter’s worst.

Eastern Chipmunk gathering deeds in autumn — Everyone knows that Eastern Chipmunks spend much of the fall storing provisions for consumption as snacks during breaks in their winter slumbers, but did you realize that those chipmunks with the best inventory will have a pronounced advantage over less successful neighbors come late winter and spring?

Male Eastern Chipmunk — Upon exiting their subterranean shelters earlier this week, Eastern Chipmunks commenced the courting ritual which includes males like this one chasing other males away from both their dens…

Female Eastern Chipmunk — …and prospective mates like this female trying to escape notice by hiding in a hollow stump.

Eastern Chipmunks — Being well-nourished throughout the winter has adequately prepared this male (right) for the strenuous activity of securing both his territory and his mate against other males.

Eastern Chipmunks Copulating — …she becomes receptive to his advances. A well-fed pair of chipmunks can complete courtship and mating within hours of emerging from their winter abodes.

February 27, 2026February 27, 2026

It’s Snow Goose Time at Middle Creek

In case you haven’t already heard, the Snow Geese are at last filtering north from the Atlantic Coastal Plain to congregate at the Pennsylvania Game Commission’s Middle Creek Wildlife Management Area in Lancaster and Lebanon Counties.

Snow Geese at Middle Creek W.M.A. — As many as 60,000 Snow Geese have been enumerated in recent days at the refuge.

Tundra Swans at Midle Creek WMA — And more than 500 Tundra Swans are making a stopover.

Snow Geese at Willow Point — When not in the fields feeding, Snow Geese are concentrated around the small area of open water on the otherwise frozen lake, making them easily observed from the Willow Point viewing area. If you’re planning to visit and have a look, don’t wait. The urge to begin their 2,000-mile journey to breeding areas on the arctic tundra is strong, and as soon as conditions permit, they’ll be resuming their excursion. This could very well be an abbreviated stay.

February 25, 2026February 25, 2026

Start Your Own Tree Nursery

Just a reminder—there’s still time to order trees and shrubs from your local county conservation district’s annual sale, but you need to act soon…

Cumberland County Conservation District 48th Annual Tree Seedling Sale

Order by Friday, March 20, 2026

Pick Up on Thursday, April 16, 2026, or Friday, April 17, 2026

Dauphin County Conservation District Seedling Sale

Order by Monday, March 16, 2026

Pick Up on Thursday, April 23, 2026, or Friday, April 24, 2026

Franklin County Conservation District Tree Seedling Sale

Order by Tuesday, March 17, 2026

Pick Up on Thursday, April 23, 2026

Huntingdon County Conservation District Tree/Seedling Sale

Order by Friday, April 3, 2026

Pick Up on Thursday, April 16, 2026, or Friday, April 17, 2026

Lancaster County Conservation District Annual Tree Seedling Sale

Order by Friday, March 6, 2026

Pick Up on Friday, April 10, 2026

Lebanon County Conservation District ALL NATIVE! Tree & Plant Sale

Order by Monday, March 2, 2026

Pick Up on Friday, April 17, 2026

Mifflin County Conservation District Tree Sale

Order by Friday, March 6, 2026

Pick Up on Wednesday, April 15, 2026, or Thursday, April 16, 2026

Schuylkill County Conservation District/Sweet Arrow Lake Conservation Association 51st Annual Seedling Sale

Order by Saturday, March 21, 2026

Pick Up on Saturday, May 2, 2026

Snyder County Conservation District Tree Seedling Sale

Order by Monday, March 30, 2026

Pick Up on Wednesday, April 15, 2026

York County Conservation District Seedling Sale

Order by Sunday, March 15, 2026

Pick Up on Thursday, April 16, 2026

If maybe you would like to order trees but you’re not quite ready to put them in the ground, why not pot them up and start your own plant nursery. It’s a great way to build an inventory of hardy stock for planting around your own property or for use in community or civic conservation projects.

Potting Sweetgum Seedlings — Earlier this week we potted up some bare-root seedlings in a mix of compost and sand to give them a head start before planting them in the ground either during the coming fall or in years to come. These happen to be some young American Sweetgum trees we purchased from a nursery in Perkasie, Bucks County, Pennsylvania.

Native Tree Nursery — After watering them in, we added our new trees to the inventory we have available for stream buffers, rain gardens, reforestation, and other rewilding projects. We’ll either stake or trim them to remedy the curved stems.

Yellow Birch Sapling — In just a season or two, we have nice robust saplings ready to install in a project or in the headquarters garden. Starting plants in the nursery gives them the size they need to improve their chances of survival.

This is one of ten Norway Spruce trees we purchased in a pack from a local conservation district sale almost ten years ago. We started each two-year-old seedling in a pot, then transplanted them into the ground a year later. All have been thriving ever since.

Since being installed as a potted sapling reared in the headquarters nursery about fifteen years ago, this sturdy Eastern Sycamore has matured and is producing seeds relished by American Goldfinches and other birds.

Eastern Sycamore and Conifers — Growing in a streamside woodland, a really massive sycamore that got its start in your nursery could continue to provide valuable wildlife habitat over a lifespan extending one hundred, two hundred, maybe even three hundred years or more. These long-lived denizens of the floodplain provide homes for such beloved breeding birds as Baltimore Orioles, Bald Eagles, Warbling Vireos, Yellow-throated Warblers, and several species of owls,…

Great Horned Owl Nest in Eastern Sycamore — …including this Great Horned Owl, seen currently incubating eggs inside a legacy sycamore that has been an active nest site among its neighboring Norway Spruces and Eastern White Pines for decades.

Yellow-crowned Night Herons at Nest — Yellow-crowned Night Herons, an endangered species in Pennsylvania, nesting in an Eastern Sycamore planted during the early twentieth century as a street tree very near the Susquehanna in mid-town Harrisburg. Ordering and planting trees today is essential for their tomorrow.

February 14, 2026February 16, 2026

Adapting to Winter Extremes

During winter’s harshest conditions, one must frequently marvel at the methods various forms of wildlife have to survive. Take a look at some of the animals we found using their life-sustaining adaptations to find food amidst the snow-covered landscape and bitter cold air.

We watched this Blue Jay digging to retrieve an acorn from beneath the tuft of leaves and dried grasses where it had apparently concealed it earlier in the season.

Blue Jay Eating Acorn — It then carried it to a nearby limb and chiseled away the husk to devour the nutritious contents. Blue Jays are known to cache hundreds or even thousands of seeds, nuts, and acorns for winter consumption. Want to see it for yourself? Just put out some unshelled no-salt peanuts and watch the jays haul them away, that is if the hoarding squirrels don’t get them first!

Like other members of the Picidae family, Red-headed Woodpeckers pry and chisel away at decaying and insect-infested trees to find food during the winter.

First-winter Red-headed Woodpecker — Like jays, Red-headed Woodpeckers including this first-winter bird are very fond of acorns and will often collect them from the ground. And like jays, they’ll cache acorns for use as a backup supply when a blanket of snow may prevent them from gathering those that remain beneath the oaks.

Native to eastern Asia, Wintercreeper (Euonymus fortunei) has escaped from mostly urban cultivation to become naturalized and often invasive in some wooded areas of the lower Susquehanna River watershed. It can be quite aggressive, usually found growing as a climbing vine or less frequently as a shrub. In the absence of native and more palatable foods, the berries are an attractive survival fare for members of the Turidae (thrush) family and other birds.

We found this and several hundred more American Robins surviving the current winter weather while feeding on Wintercreeper in a suburban woods with a heavy growth of the invasive plant.

Several Eastern Bluebirds were seen among the Wintercreeper tangles as well. They too are relying upon this non-native plant to provide at least a portion of the energy they need to make through blustery February nights.

The Hermit Thrush, a species that nests in the coniferous and mixed forests of the northern United States and Canada, winters sparingly in the lower Susquehanna valley. We found this one among the robins and bluebirds of the Wintercreeper thicket where it too was probably attracted by the supply of berries.

Frequently escaping notice in the winter woods is the Brown Creeper, another species that nests primarily in coniferous and mixed forests to our north, though it does breed in our area at scattered locations, primarily in mountainous or swampy terrain.

The petite Winter Wren exhibits mouse-like behavior as it hops and crawls among logs, rocks, and brush along the banks of wooded waterways. Like the creeper, it is primarily an insectivore, spending much of its time escaping notice searching beneath streamside structure for its daily nourishment. In summer, Winter Wrens nest in damp coniferous forests.

Seeing a Red Fox repeatedly during daylight hours is typically considered to be a sign that one may be observing a diseased animal, but we soon determined that there was nothing at all wrong with this vulpid we found patrolling a large woodland lying along the outskirts of a lower Susquehanna city.

February 13, 2026February 14, 2026

Today’s Middle Creek Snow Goose Count: One

For those of you who may be wondering if there are Snow Geese at Middle Creek Wildlife Management Area, the answer is yes—just one!

So where are the thousands of Snow Geese we’ve grown accustomed to seeing during recent decades as they gather at the refuge in February while preparing to fly north for the summer?

With much of the river and nearly all of the lower Susquehanna basin’s lakes and ponds frozen, Snow Geese and many other migratory waterfowl remain concentrated on the Atlantic Coastal Plain where salty tidewater provides ice-free conditions for feeding and loafing. In fact, some ducks, particularly diving species, may still be evacuating freshwater locations to our north such as the Eastern Great Lakes where, during the past week, even more surface area has succumbed to freezing. Look for migrants to begin pushing north in bigger numbers as soon as rising temperatures start to melt local ice. (NOAA/U.S. National Ice Center image)

February 11, 2026February 11, 2026

To Stave Off Starvation, Nip It in the Bud

It looks like the worst of the cold may be behind us. With temperatures trending upwards during the coming days and weeks, some species of wildlife will soon find their search for food made a whole lot easier.

White-crowned Sparrows spend the winter seeking shelter in dense tangles of early successional growth, particularly among thorny shrubs and vines. Extended periods with snow cover can make their search for food a real challenge, but we spotted this one hitting the jackpot on a bare patch of sun-drenched ground along the edge of a thicket of briars. It has found the earliest green buds of a clover or other herbaceous plant. Many songbirds in the finch, cardinal, and sparrow families turn to buds in late winter and early spring as a source of energy-rich sugars.

In woodlands, sweet sap will soon swell the buds of maples, much to the delight of Eastern Gray Squirrels whose favorite dining spot will suddenly become the treetops instead of the leaf litter. Often selected by property owners for their colorful autumn foliage and fast growth, the prevalence of both native and non-native maples in the suburban landscape helps more squirrels survive the winter to expand their numbers in the spring.

Nibbling late-winter buds is a daylong pastime for the hungry White-tailed Deity. While high-intensity twig browsing can alter forest ecology and practically eliminate understory growth and regeneration, bud snacking only tends to make some of the trees more stout than others. It’s similar to the trimming and snipping a bonsai artist may do to maintain a prized specimen.

Tree Shelters Protecting Saplings — Those of you installing stream buffers or reforesting all or part of your property may not want your newly planted trees turned into bonsai or lost entirely to hungry ungulates. If you’re seeking some relief from a browsing problem, you’ve got to nip it in the bud. Tree shelters offer protection during the first half a decade or more of your sapling’s new life. You can find these tubes for sale from many online sources including some of the local county conservation districts during their annual spring tree sales (which happen to be underway right now, hint-hint). Installing these plastic protectors may not only relieve you from the frustration of worrying about your new trees, it might also excuse you from risking involvement in the sometimes heated quarrel between the worshipers of the White-tailed Deity who practice sacrifice and those who religiously oppose it.

February 5, 2026

An Intermission Between Deep Freezes

With another round of single-digit and possibly sub-zero temperatures on the way, birds and other wildlife are taking advantage of a break in the extreme conditions to re-energize. During the past day, these species were among those attracted to the food and cover provided by the habitat plantings in the susquehannawildlife.net headquarters garden…

Dark-eyed Juncos, one of our numerous species of native sparrows, are sometimes called “snowbirds”, and for good reason. They spend the majority of their time on the ground searching for seeds and are particularly noticeable when the landscape is blanketed in white.

To make it through the winter, a Northern Mockingbird is again defending the garden’s supply of fruits adorning Common Winterberry, American Holly, and Eastern Red Cedar. Robins, starlings, waxwings, and bluebirds must be stealthy and quick if they want to grab a snack before the ever-alert mockingbird aggressively moves them on their way.

As they mature, our plantings of junipers, hollies, Eastern Hemlock, Norway Spruce, and Eastern White Pine offer the environs needed by evergreen-loving species like this Red-breasted Nuthatch to remain as winter residents instead of just seasonal transients.

January 29, 2026

In the Frozen Foods Aisle

For overwintering birds and other animals, finding enough food is especially difficult when there’s snow on the ground. And nighttime temperatures in the single digits make critical the need to replenish energy during the daylight hours. Earlier this afternoon, we found these American Robins seizing the berry-like cones from ornamental junipers in a grocery store parking lot. It was an urgent effort in their struggle for survival.

American Robin on Juniper — Though seldom considered ideal wildlife plants, low-growing ornamental junipers often produce an abundance of seed-containing cones that resemble berries.

American Robins Eating Juniper — In a pinch, they’ll attract dozens of robins and other fruit-eating birds as a quick source of nourishment on a windy, bitter-cold day.

American Robins Feeding on Juniper "Berries" — After all, these landscape shrubs are often derived from native species including the Creeping Juniper (Juniperus horizontalis) of Canada and the northernmost United States, a plant resembling a recumbent version of the local Eastern Red Cedar (Juniperus virginiana) with which these birds are quite familiar.

County conservation district offices will soon be taking orders for their spring tree sales. Be sure to load up on plenty of the species that offer food, cover, and nesting sites for birds and other wildlife. These sales are an economical way of adding dense-growing clusters or temperature-moderating groves of evergreens to your landscape. Plus, selecting four or five shrubs for every tree you plant can help establish a shelter-providing understory or hedgerow on your refuge. Nearly all of the varieties included in these sales produce some form of wildlife food, whether it be seeds, nuts, cones, berries, or nectar. Many are host plants for butterflies too. Acquiring plants from your county conservation district is a great opportunity to reduce the amount of ground you’re mowing and thus exposing to runoff and erosion as well!

January 21, 2026January 27, 2026

Thirty Years Ago: The Ice-jam Floods of 1996

It all started rather innocently as a typically cold early January with sheets of ice covering the river and with soils on the lands in the remainder of the lower Susquehanna watershed frozen solid. Then came the “Blizzard of ’96”, blanketing much of the valley with between 20 and 30 inches of wind-driven snow.

"Blizzard of '96" — Snowfall totals for the “Blizzard of ’96”, January 6-8, 1996. (NOAA/National Weather Service image)

In affected areas of Pennsylvania, Governor Tom Ridge closed all state roads for the duration of the snowfall event. Many would remain closed for much of the following week as drifting hampered exhaustive efforts to get impassable routes open.

Just as the recovery entered its second week, a change in the weather pattern took hold as milder air and spring-like rains hastened the melt. Clogged by snow often several feet in depth, storm sewer inlets and other drainage features failed to collect the runoff. Street and urban flooding became widespread. Some buildings, particular those with large flat roofs, experienced structural damage due to any remaining snow soaking up the additional weight of the rain. As local creeks swelled to stain snowy meadows brown, attention shifted to the icy river.

On the Susquehanna, rising waters started moving ice into accumulating piles of car-sized chunks behind dams and at choke points along the river’s course. During warmer weather, stream gauges provide a depth of water reference known as a stage (measured in feet) that corresponds to a rate of flow passing the gauge site (measured in cubic feet per second). On occasions when ice and debris block river channels during winter, these readings can fluctuate wildly and the relationship between stage and flow can become dubious. When the water is running ice-free at Harrisburg for example, a gauge reading of about 11.1 feet is indicated when the river flow rate is approximately 162,000 cubic feet per second. But due to its impact on the capability of the river channels to pass water, the presence of slow-moving and jammed ice can cause rapid and sometimes unpredictable variations in gauge readings, even when the flow rate remains steady. Impaired by an ice jam at the gauging station or just downriver, a flow of 162,000 cubic feet per second could lead to a stage measurement significantly higher than 11.1 feet, and the area of adjacent floodplain inundated by rising waters will increase to a corresponding degree. Conversely, a jam upstream of the gauging station could cause the reading to drop below 11.1 feet—at least temporarily—then look out, a dangerous surge could be forthcoming!

At Harrisburg, the ice jam behind the Dock Street Dam in January, 1996, caused devastating flooding in the city’s Shipoke neighborhood, on City Island, and in low-lying areas along the river’s west shore.

USGS Gauging Station at Harrisburg — Just upriver from the Dock Street Dam at Harrisburg, the Susquehanna at the United States Geological Survey gauging station on the east side of City Island crested at 25.08 feet on January 20, 1996. As the rising waters finally began heaving the jammed ice up and over the dam, the scouring energy of the departing glacier-like mounds would carry away two spans of the truss-construction Walnut Street Bridge on the west side of the island, and eventually collapse a third. After receding during the remainder of the day and through the night, yet another aggregation of chunked ice would cause the river to crest again on January 21st, this time at 24.66 feet. Under free-flowing conditions, these readings would correspond to a river flow of just under 600,000 cubic feet per second; that’s more than 250 million gallons per minute!

Downriver at Conewago Falls, ice jams behind the York Haven Dam and at several choke points within the riverine archipelago that extends from Haldeman Island to Haldeman Riffles in Lancaster County would be relieved as the river crested there during the afternoon of January 21st. The following photograph accurately relates the scene, minus the stench of mammalian feces and petroleum emanating from the polluted water of course.

Our friends (L to R) Rick Morton, Bob Zeager, Dan Seitz and his daughter Sierra witness the ice-choked Susquehanna River cresting below Conewago Falls on January 21, 1996. Bob awoke the previous morning inside his mobile home (left rear) to discover he was rapidly being surrounded by fast-rising water. With the ice-covered road now submerged in over three feet of river, he had no hope of getting out with his van, so he started removing clothing and a few other essentials by canoe. Dan soon arrived to move a few of his things to higher ground and de-energize both properties. We did our best to lend a hand, then we all got out of the floodplain. A short time after we had departed, Rick arrived and became concerned when he saw Bob’s van, now in almost four feet of water alongside his home. Rick parked his conveyance, also a van, on a rise in the lowland terrain, then made his way back the old Pennsylvania Canal towpath to make sure Bob wasn’t stranded. After concluding that he had already evacuated, Rick returned via the towpath to his van. He then discovered that yet another surge of quickly rising water had inundated the ice-covered section of access road by which he had arrived, so he was forced to wade out, leaving his vehicle behind. A short time later, he reached us by telephone proclaiming, “I’m out!”, and filled us in on the details. As the flood receded, Rick was able to retrieve his van on January 22nd. Bob’s van was totally destroyed and both his and Dan’s mobile homes were left uninhabitable. Though by no means their first experience with river flooding, this event proved particularly costly and stressful for Bob and Dan…the effects life-altering. The moral of the story: floodplains are for flooding, not filling, not building, and certainly not dwelling. Floodplains happen to make outstanding wildlife preserves, and that’s what this water-purifying alluvial terrace wetland is today. (Vintage 35 mm image)

January 7, 2026January 8, 2026

The Variety of Medium and Large-size Gulls Visiting for the Winter

You may find this hard to believe, but during the colder months in the lower Susquehanna valley, gulls aren’t as numerous as they used to be. In the years since their heyday in the late twentieth century, many of these birds have chosen to congregate in other areas of the Mid-Atlantic region where the foods they crave are more readily available.

As you may have guessed, the population boom of the 1980s and 1990s was largely predicated on human activities. These four factors were particularly beneficial for wintering gulls…

- 1. Disposal of food-bearing waste in open landfills
  2. High-intensity agriculture with disc plowing
  3. Gizzard Shad population boom in nutrient-impaired river/Hydroelectric power generation
  4. Fumbled Fast Food

Earthworms lifted to the soil's surface by plowing attracted Ring-billed Gulls by the thousands to Susquehanna Valley farmlands during the late twentieth century. — Earthworms lifted to the soil’s surface by plowing attracted Ring-billed Gulls by the thousands to Susquehanna Valley farmlands during the late twentieth century. (Vintage 35 mm image)

Young Gizzard Shad — Filter-feeding Gizzard Shad populations thrive in nutrient-rich waters like the Susquehanna. Their rambunctious feeding style stirs up benthic sediment deposits to release more nutrients into the water column and promote the algal blooms that often lead to detrimental eutrophic conditions. Decades ago, hundreds and sometimes thousands of gulls gathered below the river’s hydroelectric dams to feed on the seemingly endless supply of small Gizzard Shad disoriented by their passage through the turbines during electric generation. (Vintage 35 mm image)

So what happened? Why are wintering gulls going elsewhere and no longer concentrating on the Susquehanna? Well, let’s look at what has changed with our four man-made factors…

1. 1. A larger percentage of the lower Susquehanna basin’s household and food industry waste is now incinerated/Landfills practice “cover as you go” waste burial.
  2. Implementation of “no-till” farming has practically eliminated availability of earthworms and other sub-surface foods for gulls.
  3. The population explosion of invasive Asiatic Clams has reduced the Gizzard Shad’s relative abundance and biomass among filter feeders.
  4. Hold on tight! Fast food has become too expensive to waste.

The non-native population of Asiatic Clams in the Susquehanna and most of its larger tributaries exploded during the last two decades of the twentieth century. Its present-day biomass in the river is exceeded by no other macroinvertebrate species. The share of plankton and other tiny foods that the Asiatic Clam harvests from the water column is no longer available to native filter-feeders including Gizzard Shad. Hence, Gizzard Shad biomass has been reduced and far fewer are available to attract amazingly enormous flocks of hungry gulls to hydroelectric dams. (Vintage 35 mm image)

GULLS THIS WINTER

Despite larid abundance on the lower Susquehanna not being the spectacle it was during the man-made boom days, an observer can still find a variety of medium and large-sized gulls wintering in the region. We ventured out to catch a glimpse of some of the species being seen both within the watershed and very nearby.

Ring-billed Gulls on Lake Clarke — By far, most of the gulls you’ll encounter in the Lower Susquehanna River Watershed right now are Ring-billed Gulls. Some of them still drop by at the business end of the drive-thru lane looking for a lost order of fries and maybe a cheeseburger in paradise.

Ring-billed Gulls in winter plumage. — First-winter (left), second-winter (center), and adult Ring-billed Gulls on the Susquehanna.

Ring-billed and American Herring Gulls — Nearly every flock of gulls found in our area right now is composed exclusively of Ring-billed Gulls. The trick to finding other species, particularly rarities, is to look for slightly larger birds mixed among them, particularly American Herring Gulls like the first-winter (back row left) and third-winter (back row right) birds seen here. Herring and other species of similar-sized gulls seem to prefer each other’s company while on the wintering grounds.

American Herring Gulls with Ring-billed Gulls — Five American Herring Gulls with smaller Ring-billed Gulls. The bird to the upper left and the bird hunkered down to its right are adult American Herring Gulls, the three brownish birds are in their first winter.

Non-adult American Herring Gulls in flight. Always look for birds with all-pale wing tips when encountering herring gulls in flight.

Four Species of Medium-sized Gulls — Midway in size between the Ring-billed Gulls in the foreground and the first-winter American Herring Gulls in the upper left and middle right of this image is a Lesser Black-backed Gull (dark-mantled bird resting at center). The similar-sized bird in the water behind it is a first-winter Iceland Gull (Larus glaucoides), a rare visitor from the arctic.

First-winter Iceland Gull — Another look at the first-winter Iceland Gull from the previous image. Did you notice the all-white primary feathers and compare them to the dark wing tips on the Ring-billed Gulls seen here in its company?

Iceland Gull Bathing — The conspicuously pale wings of the first-winter Iceland Gull, seen here bathing in the presence of two first-winter American Herring Gulls.

Lesser Black-backed Gulls like this one observed at Blue Marsh Lake are uncommon in the Lower Susquehanna River Watershed. They are progressively more likely as you travel east toward the aforementioned Bucks County landfills where hundreds of these birds make up a core Atlantic seaboard population.

Great-black-backed Gull with Ring-billed Gulls — Great Black-backed Gulls are the most frequently encountered large gull on the Susquehanna. They’re easily identified by their enormous size and, as adults, their dark mantle.

First-winter Glaucous Gull — Rivaling the Great Black-backed Gull in size is the Glaucous Gull (Larus hyperboreus), another rare arctic visitor with pale wing tips. There are numerous reports of these unusual winter visitors from sites on Delaware Bay north to the Tullytown landfills on Delaware River where half a dozen or more have been occurring. Seen near the mouth of the Susquehanna on Chesapeake Bay at North East, Maryland, has been a first-winter bird similar to this one that we photographed at Blue Marsh Lake in Berks County, Pennsylvania.

For us, seeing a Glaucous Gull brought back memories of the last time we saw the species. It was forty-five years ago on New Year’s Day 1981 that we discovered two first-winter birds feeding on Gizzard Shad in open water on an otherwise ice-choked Susquehanna below the York Haven Dam powerhouse at Conewago Falls. Hey Doc Robert, do you remember that day?

December 21, 2025December 21, 2025

Photo of the Day

The first day of winter is the darkest day of the year. In the midst of the cold weather that accompanies it, one hardly thinks of looking for insect activity. But in subterranean environs where the temperature remains relatively constant, life goes on. We recently discovered this handsome Camel Cricket while performing some maintenance in our below-grade utility entrance. Worldwide in distribution, Camel Crickets, also known as Cave Crickets, Sand Treaders, and Spider Crickets, include hundreds of species in the family Rhaphidophoridae. Most are omnivorous residents of caves, mines, cellars, hollow logs, wood piles, wells, and other dark, temperature-stable situations where they feel their way around with their antennae while searching for food. Camel Crickets usually escape notice, keeping only nocturnal hours when venturing out from light-deprived cover and lacking the organs to produce the familiar “chirps” that call attention to other crickets during the breeding season.

December 10, 2025December 11, 2025

Observing Susquehanna Bald Eagles: A Chart for Determining Age

As part of an update to our “Hawkwatcher’s Helper: Identifying Bald Eagles and other Diurnal Raptors” page, we’ve just added this chart for determining the age of the Bald Eagles you might observe on the lower Susquehanna River and elsewhere in coming weeks.

Bald Eagle age classes in late autumn in the Lower Susquehanna River Watershed. — Bald Eagle age classes as they typically appear during late autumn in the Lower Susquehanna River Watershed. (Click the image for a full-size PDF version of the chart)

Bald Eagles in each age class often retain their fall appearance through much of the winter. However, beginning January 1st, each bird is reclassified into the next in the series of chronological plumage designations. Consequently, during the early part of the new year until a new generation of eagles is hatched in late winter and spring, there are no birds in our area designated “hatch-year/juvenile”. After fledging, these youngest eagles, the new generation of juveniles, often show little change in appearance until after their first birthday, by which time they are already classified as second-year/Basic I immature birds. For birds other than the new generation of hatch-year/juvenile eagles, the majority of the molt that produces their new autumnal appearance each year occurs during spring and especially summer, when food is abundant and the bird’s energy needs for purposes other than growing feathers are at a minimum. Hence, by the time fall migration rolls around, the next in the successive progression of plumage changes is evident. For more details and year-round images of Bald Eagles, check out our “Hawkwatcher’s Helper: Identifying Bald Eagles and other Diurnal Raptors” page by clicking the tab at the top of this page.

December 8, 2025

Cuisine to Crow About!

Red-shouldered Hawk and thigh of frog (cuisses de grenouille). — Our VIP guest, a discerning Red-shouldered Hawk, dining yet again on cuisses de grenouille (thigh of frog) at susquehannawildlife.net headquarters.

December 6, 2025December 6, 2025

Eagle Time At Conowingo Dam’s Fisherman’s Park

Wintering Bald Eagles are again congregating on the lower Susquehanna River, particularly in the area of Conowingo Dam near Rising Sun, Maryland. To catch a glimpse of the action earlier this week, we took a drive on U.S. Route 1 atop Conowingo’s impounding structure to reach Fisherman’s Park on the river’s west shore below the powerhouse.

Eagle Watching at Conowingo Dam — Scores of dedicated eagle watchers and photographers brave the raw weather to see and document the concentration of eagles that gather to feed and roost in the vicinity of Exelon Energy’s Fisherman’s Park.

Susquehanna at Conowingo Dam — The panoramic view of the Susquehanna from Fisherman’s Park offers excellent opportunities to witness Bald Eagle activity.

Immature Bald Eagles — When you arrive, it’s not unusual to hear the sounds of squabbling eagles immediately upon exiting the shelter of your vehicle. During our visit, we sighted probably 60 to 80 individuals of various age classes among the rocks and trees along the river shorelines below the dam.

Second-year (Basic I) Bald Eagle — Soon enough, we experienced a close fly-by from this second-year Bald Eagle.

Hatch-year (Juvenile) Bald Eagle — We were a little bit concerned to see only one hatch-year (juvenile) Bald Eagle among the birds at Fisherman’s Park. Perhaps the aggressive behavior of the large number of older and more experienced eagles in the area has these first-year individuals shying away. We discerned no third-year birds either, though they may certainly have been present.

Fourth-year (Basic III) Bald Eagle — A probable fourth-year Bald Eagle shows a white head with the remains of a dark line through the eye, a trait often more conspicuous in third-year birds often known as “osprey face” eagles.

Fifth-year (Basic IV) Bald Eagle — This probable fifth-year Bald Eagle has nearly lost the dark markings on the head and tail that differentiate immature birds from adults. A molt during the coming year will yield adult plumage and mark the completion of this bird’s sexual maturity.

Eagle Photographers at Fisherman's Park — Meanwhile, a little action gets the shutters clicking,…

Eagle Dogfight in the Incipient Stage — …a fourth-year Bald Eagle (top) is drawing the ire of an adult bird,…

Eagle Dogfight — …necessitating a reprisal for the taunting behavior.

To the delight of photographers at Conowingo, some of the eagles can be seen grabbing fish, mostly Gizzard Shad, from the tailrace area of the river below the powerhouse. But Bald Eagles are opportunistic feeders, and their feeding habits are similar to those of numerous other birds found in the vicinity of the dam at this time of year—they’re scavengers. Here’s a glimpse of some of the other scavengers found in the midst of this Bald Eagle realm…

Fish Crows are recognized by their nasal call. They’ll eat almost anything they can find including garbage, fish remains, discarded bait, lunch scraps, road kill, and more.

Visitors to Fisherman’s Park are warned to keep out of sight any food they may have stored in their cars. Black Vultures are known to peel rubber away from windows as they search for something to eat, a habit they possibly learned during productive forays to landfills where the edges of rubber coverings sometimes hide a freshly dumped buffet of potential sustenance.

During our stop at Conowingo Dam earlier this week, we saw only one Turkey Vulture, though more are certainly in the vicinity feeding on road kill and other carrion.

Like eagles, Ring-billed Gulls are opportunistic feeders, seen here looking for disoriented Gizzard Shad and other fish,…

Ring-billed Gull — …then quickly changing focus to check the humans along the shoreline for discarded bait or fumbled snack foods.

Juvenile Ring-billed Gull — Even young Ring-billed Gulls learn the value of watching people for activities that provide an opportunity to scavenge food.

While Ring-billed Gulls and other scavengers aren’t particularly fussy about what they eat, Double-crested Cormorants are;…

Double-crested Cormorant — …they’re targeting Gizzard Shad and other fish in the waters below the dam. Thus, we would categorize cormorants as predators, eating mollusks and other aquatic organisms as well.

Bald Eagles at Heron Rookery — But if perhaps winter isn’t your thing, don’t despair. These Bald Eagles came upon last year’s Great Blue Heron rookery on the island below the dam and it seems to be giving them some ideas. If you think like an eagle, spring is just weeks away!

November 28, 2025

Maybe They’ll Stay, Maybe They Won’t

Here are a few more late-season migrants you might currently see passing through the lower Susquehanna valley. Where adequate food and cover are available, some may remain into part or all of the winter…

During the summer, Ruby-crowned Kinglets nest in northern coniferous forests. Through the colder months, these petite songbirds can often subsist on tiny insects and other invertebrates found among the bark, limbs, and buds of leafless deciduous trees and shrubs. In our region, look for wintering kinglets in woodlands that include at least a small percentage of evergreens to provide protection from frigid nighttime temperatures.

The Yellow-bellied Sapsucker is our shiest of woodpeckers. These migrants are still quite common among stands of deciduous and mixed woods, but local numbers will soon decrease as the majority of the population continues moving along to the forests of the southeastern United States for winter.

In case you were wondering…Yes, the adult Red-shouldered Hawk continues to visit the garden pond at susquehannawildlife.net headquarters. Earlier today, we watched it plunge into the shallows after a Green Frog. We’re enjoying the privilege of having it around, so we hope it decides to remain for as long as the food supply is accessible.

November 24, 2025November 24, 2025

Windy and Dark November Skies

Those cold, blustery days of November can be a real downer. But there’s a silver lining to those ominous clouds, and it comes with the waves of black and mostly dark-colored migrants that stream down the ridges of the Lower Susquehanna River Watershed on their way south at this time of year.

For protection from predators, blackbirds including these Common Grackles typically assemble into sizeable flocks numbering hundreds of birds following the nesting season. These noisy bands of passerines are currently being seen as they move south into the Piedmont and Atlantic Coastal Plain for winter.

American Crows are now working their way into the area. To avoid falling prey to owls and other predators during the night, they form often enormous roosts in well-lit urban areas. They spend their days fanning out across the landscape in search of food, primarily relying upon human-generated fare including road kill and scraps found among trash and litter for sustenance.

Formerly confined largely to remote mountainous terrain, the crow’s close relative the Common Raven has, during this century, become more widespread and tolerant of human activity.

Second Mountain Hawk Watch — Spending time at one or more of the regional hawk-counting stations during coming weeks will afford you not only the chance to see ravens, but many of our largest raptors as well. Their migration is just now reaching its peak.

Peak numbers of Red-tailed Hawks are migrating through the area right now. Though their population is in decline overall, they may appear very common along rural roadways and in suburbia during coming weeks as they try to find prey before continuing south. Inexperienced juvenile “red-tails” are particularly vulnerable to fatal traffic mishaps and other hazards during this time. Give them some room if you can.

Early November brings the last of the season’s Osprey down local ridges. Many, including this one seen earlier in the week, will fly right up until sunset to expedite their journey to warmer climes.

Bald Eagle — Always a crowd-pleaser among the observers on the lookouts are the eagles.

Juvenile Bald Eagle — Right now, migrating Bald Eagle numbers are often exceeding a dozen birds per day at local counting stations. They include those like this one in juvenile (hatch-year) plumage as well as the various molt sequences experienced by immature eagles prior to reaching maturity.

At present, Golden Eagle numbers are just starting to build. Look for the peak of their fall migration to arrive in coming weeks. Gusty days following passage of a cold front are often your best bet for seeing these regal raptors from local lookouts.

For more information on regional hawkwatching sites and raptor identification, click the “Hawkwatcher’s Helper: Identifying Bald Eagles and other Diurnal Raptors” tab at the top of this page. And for more on Golden Eagles specifically, click the “Golden Eagle Aging Chart” tab.

November 5, 2025November 5, 2025

Photo of the Day

During these last mild evenings of fall, the trilling call of the Narrow-winged Tree Cricket (Oecanthus niveus) can still be heard among the withering growth of thickets, fields, and forest edges. As the temperatures plummet, the pulsating rate of this insect’s song slows proportionally. Below about 40 degrees Fahrenheit, there is silence.

November 4, 2025November 5, 2025

The Guiding Light

October 25, 2025

Leaf ID

Out and about doing some autumn “leaf peeping” this week?

Well, you’ll certainly want to check out Uncle Tyler Dyer’s fall foliage collection to help identify your finds…

Click the Trees, Shrubs, and Woody Vines tab at the top of this page to take a leap over to Uncle Ty’s leaf spectacular!

October 23, 2025October 24, 2025

Photo of the Day

Painted Turtles and Invasive Red-eared Sliders — Invasive populations of Red-eared Sliders (right) continue to grow and threaten numbers of native freshwater testudines including the Painted Turtles seen here to the left. Introduced primarily as unwanted pets, sliders are now freely reproducing throughout much of the lower Susquehanna watershed. Their ability to feed aggressively and grow to sizes significantly larger than those of our most-imperiled wetland species including the Spotted Turtle (Clemmys guttata), Wood Turtle, and endangered Bog Turtle make Red-eared Sliders a menace rivaling habitat loss and illegal collecting.

October 21, 2025October 21, 2025

Photo of the Day

Small numbers of Rusty Blackbirds are currently moving south through the Lower Susquehanna River Watershed. Look for individuals and small flocks feeding in damp woods and along lake and river shorelines. These uncommon birds nest far to our north in wet coniferous and mixed forests as well as willow thickets, often in muskeg or beaver pond-created habitat. Rusty Blackbirds spend the colder months in the wooded swamps of the southeastern and south-central United States. Loss of habitat has reduced their numbers dramatically, as has their misfortune to occasionally join flocks of foraging Red-winged Blackbirds and Common Grackles on the wintering grounds where all of these species fall victim to avicide poisons placed on feedlots to eradicate European Starlings.

October 18, 2025October 28, 2025

Robinson’s Invasion

As we begin the second half of October, frosty nights have put an end to choruses of annual cicadas in the lower Susquehanna valley. Though they are gone for yet another year, they are not forgotten. Here’s an update on one of our special finds in 2025.

During late June of 1863, the beginning of the third summer of the American Civil War, there was great consternation among the populous of the lower Susquehanna region. Hoping to bring about Union capitulation and an end to the conflict, General Robert E. Lee and his 70,000-man Army of Northern Virginia were marching north into the passes and valleys on the west side of the river. The uncontested Confederate advances posed an immediate threat to Pennsylvania’s capital in Harrisburg and cities to the east. Marching north in pursuit of Lee was the First Corps of the Army of the Potomac, the lead element of the 100,000-man Union force under the direction of newly appointed commander General George G. Meade.

Upon belatedly learning of Meade’s pursuit, Lee hastily ordered the widely separated corps of his army to concentrate on the crossroads town of Gettysburg. As the southern army’s Third Corps under General A. P. Hill approached Gettysburg from the west, they were met by Union cavalry under the leadership of General John Buford. Dismounted and formed up south to north across the Chambersburg Pike, Buford’s men held off Confederate infantry until relieved by the arrival of the Union First Corps. As he deployed his men, the First Corps’ commander, General John F. Reynolds of Lancaster, was struck by a bullet and killed.

General John C. Robinson Monument at Gettysburg — During the first day’s fighting at Gettysburg on July 1, 1863, the northernmost position in the Union First Corps’ line was held by its Second Division commanded by General John C. Robinson. His men would defend their right flank against attacks from Confederate General Richard S. Ewell’s Second Corps as they arrived from the north to face off against the Union Eleventh Corps which had arrived to take positions north of the town. During the afternoon, upon becoming outnumbered and overwhelmed, the Union forces would retreat south through the town to take up positions on Cemetery Hill by nightfall. Deployments extending south and east of Cemetery Hill would ultimately prove victorious for Union forces during the battle’s final day on July 3.

Lee's 1863 Invasion of the North — John C. Robinson’s Second Division “invaded” Pennsylvania as one of Meade’s lead elements charged with intercepting Lee’s Confederate Army. (National Park Service image)

If you visit the Gettysburg battlefield, you can find the General John C. Robinson monument at the site of his division’s first-day position along Doubleday Avenue at Robinson Avenue near the Eternal Light Peace Memorial. But that’s not the Robinson we went to Gettysburg to see.

Following up on our sight and mostly sound experiences with some Robinson’s Cicadas, an annual species of singing insect we found thriving at Gifford Pinchot State Park in York County, Pennsylvania, during late July, we spent some time searching out other locations where this native invader from the southern United States could be occurring in the Lower Susquehanna River Watershed.

During mid-August, we stumbled upon a population of Robinson’s Cicadas east of the Susquehanna in the Conewago Creek (east) watershed in Londonderry Township, Dauphin County, and made some sound recordings.

After pondering this latest discovery, we decided to investigate places with habitat characteristics similar to those at both the new Londonderry Township and the earlier Gifford Pinchot State Park locations—successional growth with extensive stands of Eastern Red Cedar on the Piedmont’s Triassic Gettysburg Formation “redbeds”. We headed south towards known populations of Robinson’s Cicadas in Virginia and Maryland to look for suitable sites within Pennsylvania that might bridge the range gap.

Our search was a rapid success. On State Game Lands 249 in the Conewago Creek (west) watershed in Adams County, we found Robinson’s Cicadas to be widespread.

Robinson's Cicada Habitat — Eastern Red Cedar, a probable host tree for Robinson’s Cicada nymphs, among successional growth on State Game Lands 249. Cedar thickets often become established on shallow or depleted soils on lands originally cleared for farming. They provide excellent cover as well as much needed breeding and feeding areas for birds, mammals, insects, and other wildlife.

Following our hunch that these lower Susquehanna Robinson’s Cicadas extended their range north through the cedar thickets of the Gettysburg Basin as opposed to hopping the Appalachians from a population reported to inhabit southwest Pennsylvania, we made our way to the battlefield and surrounding lands. We found Robinson’s Cicadas to be quite common and widespread in these areas, even occurring in the town of Gettysburg itself.

Robinson's Cicada Range in Central Pennsylvania — Populations of Robinson’s Cicadas (red) in the lower Susquehanna valley and adjacent areas of the Potomac watershed near Gettysburg. The Triassic Gettysburg Basin is shown in white with intrusions of igneous Triassic-Jurassic diabase in dark green. (United States Geological Survey base image)

Robinson's Cicada Habitat on Gettysburg Battlefield — Robinson’s Cicadas are common on much of the Gettysburg National Military Park property, particularly in the southern reaches where outlying areas are dense with Eastern Red Cedar growth to within several miles of the Mason-Dixon Line. In these tall walnuts and cedars along Confederate Avenue (that’s Little Round Top and its diabase boulders in the background) we recorded the following sound clip of a singing male.

Robinson’s Cicada probably extended its range into the lower Susquehanna valley in much the same way General John C. Robinson and the rest of the Army of the Potomac marched into Pennsylvania to meet Lee’s Confederates, by following the terrain of the Triassic Gettysburg Basin. Got a big stand of cedars near you? Be sure to have a listen for Robinson’s Cicadas next summer! (United States Geological Survey base image)

October 10, 2025