Scenes from a Managed Grassland Ecosystem

Pretty pictures…

Veery — Photographing Neotropical migrants as they arrive to nest in our local forests can be frustrating under closed canopies and diffused light conditions. We instead decided to focus our efforts and lenses on the grassland species at Middle Creek Wildlife Management Area where, earlier this week, several prescribed fire burns were wrapping up the spring treatments for 2026.

Warm-season grassland — Managed warm-season grassland habitat at Middle Creek Wildlife Management Area.

Already tending nests containing eggs and young, Tree Swallows are scattered around the refuge’s grasslands to welcome newly arriving migrants, and human visitors!

Middle Creek is probably the best place in the lower Susquehanna valley to see ground-nesting Grasshopper Sparrows.

Grasshopper Sparrow and Tree Swallow — It’s a behavior that occasionally puts the newcomer Grasshopper Sparrow in conflict with a well-ensconced Tree Swallow guarding its nest box.

Eastern Bluebirds squeeze in among the Tree Swallows to find a vacant nest box within which they can raise their young.

Song Sparrows may be present year-round in grasslands with interspersed growth of early successional shrubs and briars, however the populations at a given location changes as birds migrate in and out of the area seasonally. Those individuals observed nesting here in the spring and summer are not usually the same birds seen during the late fall and winter.

As a species, the Savannah Sparrow, like the Song Sparrow, may be represented in the grasslands throughout the year, though the individuals vary with the changing seasons. Unlike the Song Sparrow which nests in shrubs, the Savannah Sparrow nests on the ground among thick grasses.

Still munching on the seeds of last year’s wildflowers, American Goldfinches are pairing up around the grasslands waiting for thistle down and other fibers to be available for nest construction. They will then build a small cup within the upper limbs of a small to medium-sized tree to shelter their eggs and nestlings.

The Common Yellowthroat, one of our Neotropical warblers, will reproduce in grasslands with scattered early successional thorny shrubs to afford a safe place to construct a nest. The males sing almost incessantly from the time they arrive in late April and early May until sometime in July, or even later.

Eastern Kingbirds are arriving from tropical wintering grounds to nest in grasslands and pastures throughout the lower Susquehanna region. They are a tyrant flycatcher that will ambush insects from a perch atop a tree, shrub, or tuft of tall grass.

Northern Mockingbirds are considered a resident species, though there may be some southward movement during severe winters when foods such as berries become scarce. At Middle Creek, some of these evacuees have returned to nest along the interface zone between the grassland and early successional shrub habitats.

Nesting Horned Larks apparently take advantage of the interface between the managed grasslands and nearly bare soils in spring-planted croplands at Middle Creek. They may be one of the few, possibly the only, species of bird life to take advantage of no-till farming for nesting on the ground.

Red-winged Blackbirds not only construct nests in cattails and other marsh growth, but in dense grasses and shrubs in and near grasslands and pastures. The males are easily seen displaying their plumage as they sing from a small tree, shrub, or a cattail seed spike.

Female Red-winged Blackbird — Less frequently seen is the female Red-winged Blackbird. She spends the majority of her time in the nest, but will periodically come out to join the ruckus when an intruder is being scolded into leaving the premises.

Another member of the blackbird family is the Eastern Meadowlark. It too is an energetic singer during the breeding season. Meadowlarks build their nests on the ground, often in pastures of cool-season grasses where harvests prior to August are fatal to eggs and young. Middle Creek’s managers delay harvests to allow the birds enough time to complete their reproduction cycle.

Another blackbird is the Bobolink, an obligate grassland specialist and a Neotropical migrant. One of its few uses for trees and shrubs is as a place to burst into display and song, though it will also perform these rituals on the wing and among the grass.

Bobolinks — As the males arrive, competition for suitable nesting sites among the grasses becomes intense, even before a female is anywhere in sight.

Did you know the Baltimore Oriole is a blackbird? Well, it is.

Baltimore Orioles — Competition for these ideal sites can get quite animated.

Western Cattle Egrets and Geese — It’s an unusual experience, watching Western Cattle Egrets feeding in a field of cultivated cool-season grasses alongside Snow Geese, though they certainly aren’t looking for the same thing.

We’ll have more on the Western Cattle Egrets and other interesting migrants at Middle Creek in an upcoming post. Check back soon!

May 8, 2026May 8, 2026

Common Dandelions Are as Good as Gold

American Goldfinches Feeding on Common Dandelion Seeds — Please tell us you’re not putting herbicides and other toxic chemicals on the dandelions and other antioxidant and anti-inflammatory plants in your lawn and garden,…

April 22, 2026April 22, 2026

The dynamics of water’s storage and movement on earth, as well as its transitions through the primary states of matter—gas, liquid, and solid—are known as the water cycle. Understanding how life-supporting water progresses through the global biosphere can provide each of us with a greater appreciation of how fragile a resource clean water is in the presence of 8.3 billion wasteful and polluting humans.

This graphic created by the United States Geological Survey illustrates many of the components of the water cycle’s complex processes. Have a look…

For a PDF version which includes a more detailed description along the bottom margin, click here. We like it so much, we’ve added it to this webpage’s sidebar for future reference.

April 14, 2026May 13, 2026

Managing a Grassland Ecosystem

If you’ve visited Middle Creek Wildlife Management Area anytime during the past month, you may have noticed quite a bit of activity around the large pole-mounted nest boxes placed out in the open fields.

American Kestrels at nest box — American Kestrels, a male and female, at a nest box at Middle Creek Wildlife Management Area.

Kestrels competing for nesting sites and territory. — Within the past week, we noticed that kestrels are still competing for nesting sites and territory, driving away unwanted trespassers. A pair of kestrels seemed to be occupying each of the four box sites we observed. That’s good news, but the presence of these man-made nest cavities is in no way wholly responsible for this positive response from these declining birds. It’s a matter of habitat, much needed grassland habitat.

Cool Season Grasses — Cool-season grasses including fescue (Lolium species) and non-native Orchard Grass (Dactylis glomerata) mature by late spring. If left standing, they continue to provide indispensable habitat for grassland wildlife through the summer. Mowing early and often for hay harvest has rendered most cool-season meadows death traps for nesting birds. By delaying cuttings until at least early August, ground-nesting birds are given adequate time to fledge their young and get the juvenile birds strong enough to fly away from a set of spinning blades.

Grasshopper Sparrow in Timothy — A male Grasshopper Sparrow sings to demarcate its nesting territory in a stand of Timothy, an introduced species cultivated for harvest as hay. An insectivore during the breeding season, he and his mate will attempt to raise their brood exclusively within the cover of these cool-season grasses.

Orchard Grass with Black-eyed Susans — Prior to being mowed, Orchard Grass provides the short, dense cover meadowlarks and other ground-nesting grassland birds need to successfully reproduce. Growing a cool season grassland can be as easy as delaying the mowing of a pasture, field, or oversize lawn until August, then have a farmer friend come and take off a cutting or two of hay or straw to prevent woody plants from becoming established.

Warm-season Grasses — More durable stands of native warm-season grasses including Big Bluestem, Indiangrass, Switchgrass, and Little Bluestem thrive in the summer heat and provide wildlife habitat throughout the year. These perennial “prairie grasses”, fed by root systems five to eight feet deep, are especially drought tolerant . From these entrenched anchors, the plants would quickly bounce back after the once great herds of hungry bison had grazed the landscape bare of surface vegetation before moving on. This adaptation also assured “prairie grass” regeneration following naturally occurring seasonal fires, events mimicked in eastern North America by its pre-Columbian human residents. They used recurrent fire to perpetuate early successional habitat for wildlife propagation, foraging, and agriculture. Today in the lower Susquehanna watershed, establishing warm-season grassland meadows requires soil prep and seeding to get things going again.

Precribed Burn — To prevent succession, warm-season grassland parcels are most commonly maintained using applications of prescribed fire every 3 to 5 years. Among their benefits, these burns invigorate native vegetation while inhibiting the invasive tendencies of many non-native plants. Well-planned periodic fire can significantly reduce fuel accumulations, particularly in tinderbox woodland tracts managed as fire-free zones for the past century or more. Many forest trees including oaks rely on sporadic fire events for regeneration.

LEARN HOW LAND MANAGERS UTILIZE PRESCRIBED FIRE

This coming Saturday, April 18, 2026, beginning at 10 A.M. (rain date April 25), the Pennsylvania Game Commission is hosting a “Prescribed Fire Festival” at Middle Creek Wildlife Management Area. Be certain to come out to the visitor’s center at 100 Museum Road, Stevens, PA, for this event. Land managers will be there to answer questions and to explain the planning and preparations involved in overseeing a prescribed burn. There will be guided walks of habitats preserved using fire of varying intensities. You’ll see the equipment and protective clothing used by certified personnel to administer a live prescribed fire burn right before your eyes. Then you can have lunch—food trucks will be available on site.

Prescribed Fire Demonstration — Visitors witness a prescribed fire demonstration at the Pennsylvania Game Commission’s Middle Creek Wildlife Management Area in 2025.

After the burn demonstration, why not go for a walk or drive around the refuge. You can take note of how grassland and early successional plant communities are responding to previous doses of prescribed fire…

Greening up a week or two after the burn, Wingstem is blooming by June in areas treated using prescribed fire earlier in the spring.

Another scene from June: Four-foot-tall Joe-Pye-Weed amidst lush growth of goldenrod in early successional habitat where a prescribed burn eliminated accumulating wildfire fuel and turned back the growth of invasive plant species in March.

And how the grassland animals respond as well…

Ring-necked Pheasants in early successional habitat maintained by the periodic application of prescribed fire.

Eastern Cottontails prosper in the mosaic of warm-season grasses and early successional thickets on lands sustained using prescribed fire. Rabbits are herbivores, primary consumers eating mostly legumes and other plants, the producers that through the process of photosynthesis convert the energy of the the sun into food energy.

Other small vegetation-eating rodents including mice and voles thrive in managed grasslands. Similar in appearance are the shrews. Though seldom noticed, Northern Short-tailed Shrews spend day and night foraging for food, even in the shallow waters of wet meadows and thickets. Unlike the aforementioned herbivorous rodents, shrews are insectivores, secondary consumers feeding mostly on primary consumers including a variety of insects and other arthropods.

Some years ago, we found this tiny Masked Shrew (Sorex cinereus) in a grassland area being preserved using prescribed fire. Like other shrews, Masked Shrews are secretive, but always on the go. They feed constantly to fuel their vast energy requirements, sometimes consuming three times their body weight in a single day. But their voracious appetite can get them into trouble, causing these incessant eaters to encounter numerous potentially infective parasites during their non-stop foraging missions.

Female American Kestrel — Patrolling the grasslands is the female American Kestrel, a secondary consumer. She’s on the lookout for primary consumers including large insects like grasshoppers or crickets. But perhaps more likely is a small rodent whose less-than-ideal vigor may cause it to slip up, creating an easy target. If she selects a careless shrew as her prey, she may be assuming the role of a tertiary consumer, eating a secondary consumer (the shrew) that fed on insects (the primary consumers) that derived their energy from photosynthesized plant matter.

The strictly nocturnal American Barn Owl (Tyto furcata), another secondary and sometimes tertiary consumer, takes the night shift, hunting unwary voles, mice, and shrews, often by sensing the sounds they make among runways in the grass. As a native predator in its favored habitat, the owl’s selection of each victim actually helps to keep the prey species’ population healthy, eliminating the weak and vulnerable to provide a qualitative service to the surviving wildlife of the grasslands. While we may not think of the barn owl as a direct consumer of insects, its positive influence on insectivorous shrew populations makes it an important functionary in maintaining balance in the ecosystems it calls home.

Male American Kestrel — As food becomes increasing plentiful in the grasslands, a female kestrel will remain mostly out of sight, performing the majority of the egg incubation duties while her colorful mate stands guard nearby.

The fate of an avian predator such as a kestrel lies at the mercy of the fate of its quarry. Because, you see, the sun’s energy, after being converted to chemical energy by photosynthesizing plants, flows upward through the trophic levels of the food chain—herbivores (primary consumers) such as rodents and insects to carnivores (secondary and tertiary consumers) including kestrels. Grasslands, when abundant and diverse, are correspondingly abundant and diverse with small mammals and insects and will therefore support thriving populations of American Kestrels and other predators. These secondary and sometimes tertiary consumers fulfill a role in cultivating healthier populations of their prey—the primary and secondary consumers in the food web—as a balanced component of a flourishing grassland ecosystem. Sparse and fragmented grasslands, on the other hand, beget negligible small mammal and insect populations, are stricken with broken food webs, and champion few if any American Kestrels or other predators. If the land it occupies is neat, tidy, manicured, exploited, or sprayed sterile and dead, the energy flow cycle of the ecosystem is dead as well. There’s nothing animal introductions, reintroductions, rescues, culling, stocking, or harvesting can do about it, because in the end, it’s all about the habitat.

April 1, 2026May 16, 2026

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 flow regime 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 must then 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 vast mosaic of riffles and pools in a river this size offers tremendous opportunities for a diverse array of aquatic 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 (fluvial) 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 provide essential habitat for a wide variety of small fish and invertebrates while also consuming 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 at Chiques Rock. 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 across the diabase boulders at the York Haven Dam and Conewago Falls, a high-gradient segment of the Susquehanna.

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

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

Susquehanna Flooding at Chiques Rock — As the flood surges through the riffle and pool complex at Chiques Rock, the high stream gradient maintains a velocity in the water column sufficient to keep additional sediments in suspension until they reach the low-gradient river segment just downstream at Washington Boro, site of a naturally occurring lateral bar area known as the Conejohela Flats. These bars now lie within the man-made depositional zone known as “Lake Clarke”. Created nearly a century ago by construction of the Safe Harbor Dam, this impoundment is accumulating astounding volumes of nutrient-loaded sediments that continue to encapsulate the flats within a stream-impairing delta.

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 both the river and its tributaries, smaller dams including dangerous low-head dams maintain water levels for boating and recreation. They too create 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 reservoirs. 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 Clarke”, the impoundment created by Safe Harbor Dam. While they may find this spot advantageous for loafing, the food supply over the sediment-buried 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 or continue downriver to the Chesapeake at full strength when the dams are full. Alleviating the sediment aggregation problem within the river’s impoundments is a 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, non-native Rusty Crayfish when they find them in our lotic waterways.

TIME TO CLEAN UP OUR ACT

WHERE DOES YOUR STORMWATER GO?

Channelized Urban Stream — **Channelized Urban/Suburban Streams Function as Sewers.** They have no attached lowlands or floodplains to absorb, purify, and infiltrate runoff from rain events. Pollutants including litter, pet waste, lawn chemicals, tire-wear particles, hazardous fluids, and sometimes untreated human excrement flush unchecked from the municipal storm drainage system into the waterway. Thermal shock from summer downpours washing across sun-heated pavements can kill temperature sensitive fishes and other aquatic life. Nutrient and sediment loads from these impaired tributaries later accumulate downstream in low-gradient segments of the Susquehanna, turning the river into an open-air cesspool. Aggressively working to implement projects that eliminate these sources of pollution are the only effective way to keep the problem from getting worse. Making things better requires a lot more dedication and effort. (United States Geological Survey image by Frank Ippolito)

RIPARIAN BUFFERS MAKE A DIFFERENCE…WIDER IS BETTER

FLOODPLAIN RESTORATION

Regardless OF HOW LONG YOU’VE BEEN CONDITIONED TO THINK OTHERWISE, THIS IS A DYSFUNCTIONAL, POLLUTED CREEK—AND IT NEEDS HELP

RESTORED TO ITS HISTORIC FUNCTIONS

Floodplain and Stream Restoration — On an adjacent segment of the same creek, this legacy sediment removal project restored a braided meandering channel and connected it to its newly liberated, historic floodplain. In just their second year, the fluvial wetlands are effectively absorbing stormwater and sequestering nutrients as an attached component of the stream’s riffle and pool complex. During our visit earlier this week, we found American Toads, Northern Leopard Frogs (Lithobates pipiens), and Northern Spring Peepers breeding here. It’s just as Castor canadensis would have it!

“STOP HEMMING AND HAWING AROUND ALREADY”

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

Impaired Stream — Here’s a polluted stream in a pasture with grazing livestock. The site is a former mill pond within which the creek eroded a channel following removal of the dam. The animals defecate and urinate where access to water is gained at a broken down embankment of the nutrient-loaded legacy sediments deposited in the pond more than a century ago. It’s a haphazard form of animal husbandry and a reminder that all it takes is just one stubborn jackass to foul up the whole waterway.

DIRECT SOURCES OF NITROGEN (AMMONIA) POLLUTION IN STREAMS

DID YOU KNOW that a dairy cow produces about 80 pounds of waste (excrement and urine) every day?

DID YOU KNOW that a horse produces about 50 pounds of waste (excrement and urine) every day?

DID YOU KNOW that a human produces about 3 to 4 pounds of waste (excrement and urine) every day? The exceptions, of course, are those who continue to insist that raising farm animals in and alongside a body of water is okey-doke—a harmless practice. These individuals tend to retain the former constituent of human waste and are thus full of it.

“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 creek segment’s pollution woes have been mitigated. Do you have a neighbor needing this type of remedial work on their farm? Encourage them to contact your local county conservation district office or volunteer waterways restoration organization for assistance. Various programs provide financial assistance covering all or most of the costs of stream improvement as well as monetary incentives for helping to clean up the water.

AND FINALLY

WHEN IT COMES TO BUILDING DAMS ON LOTIC FRESH WATERS…

…LEAVE IT TO THE BEAVERS

North American Beavers (Castor canadensis) create habitats that connect the riffle and pool regime of a low-gradient stream to a surrounding fluvial wetland that retains sediments, cycles nutrients, and provides essential habitat for hundreds of plant and animal species. Floodplains are for flooding, and if a beaver floods an area, you can be guaranteed that it was already part of a floodplain. You see, beavers don’t encroach upon humans, it’s humans engaging in the encroachment upon beavers. (National Park Service image)

MAD HATTERS

DID YOU KNOW that even before the landscape was cleared for farms and a supply of timber, and before mill dams on local creeks began accumulating soil runoff from the consequently barren hillsides, all the North American Beavers, the keystone species of lower Susquehanna stream ecology, were killed and sold to make hats? It’s no wonder things are fubar!

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

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.

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.

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.

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 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 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 21, 2025November 21, 2025

Photo of the Day

Peak numbers of Fox Sparrows are now moving through the lower Susquehanna valley on their way south. Nearly as large as our Catharus thrushes, these native songbirds are among the last of our regularly occurring autumn migrants. In tangled dense thickets along the edges of fields and woodlots, small numbers may linger into winter eating berries and the seeds of herbaceous plants.

November 17, 2025November 17, 2025

Photo of the Day…Again

November 17, 2025November 17, 2025

Photo of the Day

November 6, 2025November 8, 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 4, 2025November 5, 2025

The Guiding Light

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 10, 2025

Changes Following the Season’s First Frost

Having experienced our first frost throughout much of the lower Susquehanna valley last night, we can look forward to seeing some changes in animal behavior and distribution in the days and weeks to come. Here are a few examples…

Unlike their close relatives the Tree Swallows, which include berries as well as invertebrates in their diet, Northern Rough-winged Swallows are strictly insectivores and will find it necessary to promptly move south to assure a frost-free environment where they can secure an adequate supply of food. Their one alternative: find a local sewage treatment plant where warm water attracts populations of flying insects through the remainder of autumn and maybe into winter.

Warblers too are insect eaters. Look for most of our dozens of species to evacuate the area in coming days and leave behind only the Yellow-rumped Warbler, another bird with a fondness for berries during cold weather. Into the winter months, they remain in small numbers in habitats with an abundant supply of berries like Poison Ivy, holly, wild grape, bittersweet, and Eastern Red Cedar. For lingering Yellow-rumped Warblers, thickets of cedars and other evergreens provide essential protection from frigid nighttime winds.

This Eastern Chipmunk will soon feel the pinch. Instead of eating the sweet, fruity portions of Mile-a-minute Weed berries, it’ll have to get serious about stocking its den with larger seeds, acorns, hickory nuts, and other foods to snack on through the winter. Better get busy, little friend!

September 27, 2025

Photo of the Day

Juvenile Rose-breasted Grosbeaks — These juvenile Rose-breasted Grosbeaks are among the last big southbound push of Neotropical migrants we’ll see moving through the lower Susquehanna valley in coming days. Be certain to get outside and have a look.

September 22, 2025September 22, 2025

Migrants Seeking Shelter to Weather the Storm

Less than ideal flying conditions can cause some of our migrating birds to make landfall in unusual places. Clouds and gloom caused a couple of travelers to pay an unexpected visit to the headquarters garden earlier today.

Here in our urban oasis, this Northern Parula was our first warbler of the season. We noticed it gleaning small insects from the leaves and stems of the taller trees.

Our resident Carolina Chickadees made good foraging companions for our temporary guests.

Be sure to keep an eye open for visiting migrants in your favorite garden or park during the overcast and rainy days ahead. You never know what might drop by.

September 12, 2025September 12, 2025

Tropical Treats and an Early Surprise

Crisp cool nights have the Neotropical birds that visit our northern latitudes to nest during the summer once again headed south for the winter.

Flying through the night and zipping through the forest edges at sunrise to feed are the many species of migrating vireos, warblers, and other songbirds.

A Tennessee Warbler peers from the cover of a Staghorn Sumac (Rhus typhina), a small native tree which is not, as many assume, a poisonous plant. Staghorn Sumac is in fact an excellent wildlife species with brilliant autumn colors.

Though its breeding season has come to an end, this southbound Yellow-throated Vireo was found singing its heart out in the limbs of a Staghorn Sumac early this morning.

Black-throated Green Warblers are particularly numerous right now. To see them, visit a ridgetop forest clearing at sunrise.

As the nocturnal migrants fade into the foliage to rest for the day, the movement of diurnal migrants picks up the pace.

Southbound flights of Ruby-throated Hummingbirds are reaching their peak this week with chilly temperatures hustling them along. Remember to keep your feeders clean and your nectar fresh through at least early October; they may really need the supplemental energy.

Migrating Broad-winged Hawks, sometimes traveling in large flocks known as kettles, seek out thermal updrafts to gain altitude before gliding away on a southwest heading bound for Houston, Texas. Once there, they’ll make a turn to the south and follow the gulf coastline toward the tropics for winter.

While on the crest, you might notice that the Neotropicals aren’t the only bird species heading through. Migrants like this Sharp-shinned Hawk are beginning to show up in increasing numbers with a peak expected in about two to three weeks.

To find a hawk-counting station near you, check out our “Hawkwatcher’s Helper: Identifying Bald Eagles and other Diurnal Raptors” page by clicking the tab at the top of this page. And plan to spend some time on the lookout during your visit, you never know what you might see…

Second-year Golden Eagle — This very early Golden Eagle surprised observers at Second Mountain Hawk Watch in Lebanon County, Pennsylvania, this morning. It appears to be an immature, more specifically a second-year bird beginning molt (replacing its innermost primaries), so it may not have traveled all the way to the eastern population’s breeding areas in northern Canada for the summer. Instead, it may have wandered the vast wilderness hundreds of miles further south. Expect to see these regal eagles more regularly when adults and hatch-year juveniles from the nesting region start passing through our area, primarily during the period between Halloween and Thanksgiving. In the meantime, you’ll have time to check out our “Aging Golden Eagles” page by clicking the tab at the top of this page.