As they travel between coastal wintering ranges and breeding territories in Canada and Alaska, vast numbers of shorebirds pass through the lower Susquehanna region each spring and fall—though few stop here to rest, feed, and provide us with an opportunity to observe them. Prior to the construction of man-made dams and other alterations on our lotic (flowing) waterways including the river, shorebirds took advantage of lateral bars, stream deltas, and other alluvial deposits as places to loaf and re-energize. Before they were drained and filled, some of the valley’s wetlands probably included sparsely vegetated flats where shorebirds could drop in for a brief visit. Previous to their extirpation from our region, North American Beavers were the primary providers of quality habitat for shorebirds and other migrating waders on our lotic waters. Their widespread network of dams, pools, and marshes maximized floodplain function by keeping streams thoroughly connected to their wetlands, nurturing plant communities that not only provided food and shelter for the beavers and other wildlife, but provided superb buffering against erosion while protecting against sediment and nutrient imbalances in lower Susquehanna waterways.
Beaver dams need not be large, particularly on low-gradient streams where a structure like this is sufficient to create a pool with depth adequate for building and maintaining a lodge and transporting leafy branches and other food items by water.A beaver lodge assembled in a pool with less than three feet of water, deep enough to provide the family with a measure of protection against terrestrial predators.Beaver pool ecosystems provide homes for hundreds of species of plants and animals, including migrating shorebirds and other waders.Mud flats in the margins between emergent shrubs and herbaceous plant growth attract migrating shorebirds like this Solitary Sandpiper to the abundance of invertebrate life. Seasonal movements of migrating shorebirds regularly coincide with the reductions of water levels in beaver pools which typically occur between May and September each year.During its southbound migration in September, a Least Sandpiper searches for arthropods and annelids as it visits a food-rich puddle along the periphery of a beaver pool.A Pectoral Sandpiper feeds in shallow water near a stand of Common Cattails in a beaver pool.During migration, rails including the Sora are attracted to dense emergent vegetation in beaver pools. Some will nest in these rodent-managed refugia.Green Herons visit beaver pools during migration and, due to the reliability of the food supply, will often nest in their vicinity.
So how did this happen? How did the North American Beaver become a keystone species—an animal upon which the majority of other life forms within its ecosystem are so reliant? Well, it’s largely due to the fact that our beavers aren’t particularly fond of a constant stream of noise. More specifically, they don’t like the sound of running water in places where they intend to build and maintain a lodge. And so, as they begin to place sticks, mud, limbs, stones, and other materials within a noisy riffle on a stream, they create a dam, and behind it a pool—a pool that is particularly advantageous for protecting their home and providing a means of conveyance for their construction materials and food supplies.
On a high-gradient segment of stream, beavers will create a cascading series of pools. Because water filters through a beaver dam instead of spilling over it, the work of these meticulous rodents soon silences the sounds of water changing altitude. No more sonorous riffle.Quiet please. High seasonal stream flow and damage from storms may create areas where water begins to erode the structure of the dam. Where this condition persists, an adult beaver will soon mend the breach, just to quiet things down. Why would beavers demand such a hush upon their domain? Well, they have poor eyesight, but their hearing is excellent, and they rely upon it to detect danger.The Louisiana Waterthrush (Parkesia motacilla), one of our earliest-arriving warblers, nests in forests along clear, high-gradient streams. In mid-April, we found this individual and three others squabbling over a breeding territory adjacent to the series of cascading beaver pools shown in the previous images.Native denizens of coldwater streams, neither the Brook Trout nor the Eastern Blacknose Dace has any difficulty finding its way through the voids in beaver dams to ascend and descend the sequence of pools.On a low-gradient segment of stream, a dam just over a foot in height may be sufficient to create a beaver pool of considerable size. Resembling the water-logged muskeg of the far north, well-established beaver pools form boggy habitats familiar to migrating shorebirds.Water levels in the pools usually drop along with the stream’s base flow as soon as the effects of the spring thaw and rain showers subside. Feeding areas in shallow water and on muddy ground are often revealed just in time for northbound shorebirds and other waders to stop by in late April and May. These conditions often persist through the growing season and the fall migration of these birds which begins as early as late June and sometimes extends into October.Where the pool inundates standing timber such as Red Maple and other species not used by beavers, the dead snags provide vital feeding areas for birds and other wildlife. Cavity nesters like this Tree Swallow seldom find suitable natural housing elsewhere.The mosaic of marshlands and braided stream channels within the beaver pool complex supports an abundance of aquatic life including these breeding Eastern Newts, seen here surrounded by the exuvia left behind following a massive hatch of alderflies (Sialinae). Alderflies are a stream inhabitant during their larval stage and are indicator of clean water conditions.A modern-day example of the way fully functional stream floodplains used to look in the Lower Susquehanna River Watershed. Though the pools may appear pond-like during the cooler and wetter months of the year, by summer the water levels behind the beaver dams recede as the base flow of the stream wanes. Now the true nature of the marsh, shallow pool, and braided stream complex is revealed. Unlike most man-made dams that set a fixed pool elevation regardless of flow by discharging water over the top of the structure or through a spillway or gate, beaver dams merely throttle the flow through their porous construction. Unless the beaver begins plugging small leaks as fast as the stream flow ebbs, the water level in the pools will drop. So they’re not left high and dry, lodges are located in the deepest pools, usually in close proximity to the dam and/or one of the stream courses. Though not inundated during the dry season, the soil in the pool complex is almost always damp and plants grow vigorously there, sequestering nutrients and retaining sediments in beneficial deposition patterns that actually inhibit erosion of the riparian landscape. These streams and floodplains retain their hyporheic zone and freely exchange water with the underlying water table and aquifer. It’s the ultimate floodplain management system, and the beavers don’t even know their doing all the work. (Google Maps base image)Where another high-gradient segment of stream enters the main pool complex, beavers have created an additional series of cascading pools. The impoundments created by these dams help diffuse stormwater energy and process more nutrients and sediments within the floodplain’s wetland vegetation system. (Google Maps base image)Beaver pools often refill as stream flows increase following autumn rains. The stockpiles of vegetative foods that grew within the beaver’s domain through the summer then become flooded and are a prime source of nutrition for not only the beavers, but waterfowl during both their autumn and spring migrations. Gleaning and probing Sandhill Cranes often find these habitats to their liking as well.
While North American Beavers have returned to the region, most live as “bank beavers”, residing in the river and larger creeks of the valley where they excavate shelters among the roots of Black Willows and other shoreline trees and shrubs. Floodplain encroachment, legacy sediment deposits, and just plain human intolerance have all conspired to prohibit North American Beavers from performing their magic on smaller local streams. For migrating shorebirds, this continued absence of beaver dam ecosystems has turned much of the lower Susquehanna valley into “flyover country”. Those travelers that do stop to rest and feed concentrate at the few favorable locations such as the lateral bars and the hydroelectric dam-created delta at the Conejohela Flats on the river in Lancaster County. But centralization has its drawbacks. Migrants spending time at concentration points may have a greater chance of contracting and spreading disease. Protracted heavy foraging can degrade these habitats. And over time, features such the lateral bars and delta deposits, including those on the Conejohela Flats, transition into other habitats—riparian forests. A more widespread selection of favorable stopover points for shorebirds, waders, waterfowl, and other migrants is certainly desirable.
IMITATION IS THE SINCEREST FORM OF FLATTERY
Until public sentiment sways in favor of the North American Beaver, wildlife managers are mimicking some of the attributes of their sound-inspired installations.
Created by excavating a depression in heavy clay soils, this new impoundment at the Pennsylvania Game Commission’s Middle Creek Wildlife Management Area collects water directly from rainfall and from surface runoff. Its depth at no point is greater than about two or three feet. During the driest times of the year, this space will be a mudflat, and a haven for migrating shorebirds.
Shallow-water conservation impoundments designed, constructed, and managed for migratory waterfowl and waders including shorebirds are not what we typically refer to as ponds—though they are lentic (still) waters. Similar shallow freshwater impoundments at our National Wildlife Refuges are referred to as pools by the United States Fish and Wildlife Service, but smaller versions like this example at Middle Creek very closely resemble the prairie potholes created by glacial scour in the north-central United States and adjacent portions of Canada. Many populations of migratory birds are familiar with pothole ecosystems and, like the beaver pools and marshes, have relied upon them as waypoints along their journeys for centuries.
Impoundments most beneficial to migrating waterfowl and waders including shorebirds are shallow in depth. They lack the deeper waters of a pond or lake and thus have no limnetic (open water) or aphotic zones. Managed throughout as a littoral zone, impoundments grow plants in shallow water or on damp soil through the summer months to chew up nutrients accumulated in waste deposited by visiting birds. This vegetation is then flooded from late fall through early spring as forage habitat for migratory waterfowl. The timing of the fluctuations in water levels approximates those of the beaver pools and marshes on lotic (flowing) waters.A gate assembly is a water control structure installed to provide seasonal management of the water levels in a conservation impoundment. More than once, beavers have heard the sounds of tumbling waters inside these types of devices and tried to dam them up!
You’ve heard the line, “If you build it, they will come.” Well, it’s true. Here is a sample of the activity witnessed during the past two weeks at the new impoundment completed just several months ago at Middle Creek Wildlife Management Area along the tour route just beyond the “Stop 3” overlook.
The ubiquitous Snow Geese were among the first migratory occupants of the new impoundment. A few are currently lingering in the vicinity.Ducks soon followed. These Blue-winged Teal were among the last to pass through earlier this month.Wilson’s Snipe were among the first species of migratory shorebirds to visit the new impoundment at Middle Creek……as were Killdeer, a species which nests nearby.Then, earlier this month, flocks of shorebirds including these Least Sandpipers were arriving to feed and rest.Least Sandpipers search for small invertebrates in shallow water and exposed soil.A Least Sandpiper (left) and a Semipalmated Sandpiper (right).Not all shorebirds seen by themselves are alone, and that includes the Solitary Sandpiper.Here’s a Solitary Sandpiper (right) feeding alongside a Least Sandpiper (center) and a White-rumped Sandpiper (left).A Least Sandpiper (left) and a White-rumped Sandpiper (right).Rare in our area during spring, the White-rumped Sandpiper (Calidris fuscicollis) flies north using the central flyway, then heads south along the Atlantic flyway in the fall, when it tends to be more regular here.Rocking and teetering along as it looks for food, the Spotted Sandpiper may be one of the easiest of shorebirds to identify.Chunky little Dunlin (Calidris alpina) with their conspicuously down-curved bills are another easy-to-identify species, particularly in the spring when their breeding (alternate) plumage includes a black belly.Black-bellied Plovers acquire a handsome set of plumage in the spring as well.Killdeer too are plovers and this pair appears to have taken up residence on barren ground along the periphery of the new impoundment.The Semipalmated Plover doesn’t have nearly the flair for ornament its close relatives the Killdeer do; these little shorebirds wear only one ring around their neck instead of two. Think this plover is cute?,……then check out this newly hatched Killdeer. It starts life with just one necklace too, but acquires a second as it grows. Look at those legs! (If you visit the new impoundment at Middle Creek, drive slowly and please watch where you’re going. Baby Killdeer and other young birds, as well as mammals and turtles, are commonly crossing the paved surfaces right now.)Speaking of legs, here’s one of dozens of Lesser Yellowlegs that visited the new impoundment during their recent northbound travels.Though less numerous than the smaller Lesser Yellowlegs, a Greater Yellowlegs seldom goes unnoticed when dropping by the man-made pothole habitat.Have trouble telling a Greater Yellowlegs like this one from a Lesser Yellowlegs? Look for the heavier, longer bill on the former, as well as dark barring along its flanks below the wings while the bird is in breeding (alternate) plumage during the spring migration.Everyone likes to see something unusual every now and then, and this impoundment delivers. Just yesterday, we photographed this migrating Wilson’s Phalarope (top center) among two Least Sandpipers (top left and right), a Lesser Yellowlegs (left and slightly forward of the phalarope), and a White-rumped Sandpiper (foreground).Renowned for spinning in circles as they feed in shallow water, Wilson’s Phalaropes (Phalaropus tricolor) passing through the lower Susquehanna basin are headed toward nesting areas in the prairie wetlands, including potholes, of the northern United States and adjacent sections of southern Canada.
Species of wildlife in addition to shorebirds and waterfowl have already found the new impoundment favorable…
Pairs of breeding Spot-winged Gliders (Pantala hymenaea), seen here in tandem while ovipositing, were swarming the impoundment after arriving earlier this week. These dragonflies are ofttimes unpredictable nomads and are similar in appearance to the usually more numerous Wandering Gliders. To recolonize seasonal portions of their range, both are famous for hitching a ride en masse on storm systems. They share the behavior of finding ephemeral and new bodies of water favorable for egg laying due to their low density of aquatic predators.We watched this Snapping Turtle arrive to apparently find the newly created waters to its liking. Snapping Turtles are important consumers in a wetland ecosystem. Larger specimens may fill the role of an upper trophic level or apex predator, eliminating vulnerable mid-level consumers including other Snapping Turtles.Because it bounces its tail up and down like a Spotted Sandpiper, you may at first glance mistake an American Pipit for a shorebird. Long known as the Water Pipit, these songbirds have been visiting the impoundment while migrating north and stopping to feed in nearby croplands.Seen here with Least Sandpipers is a visiting Glossy Ibis.Sometimes twenty or more of these mostly coastal waders have made a pit stop at the “new Middle Creek pothole”, though none have thus far chosen to remain long. Apparently, food sources sufficient to sustain a bird of their size have yet to develop in its benthos.Western Cattle Egrets visiting Middle Creek this spring have been frequenting the new impoundment.With still little in the way of insects such as grasshoppers available in the surrounding landscape,……cattle egrets are looking to find prey like this Green Frog.Many have been observed hunting the adjacent grasslands..Where small mammals, mostly Meadow Voles, are being taken in abundance.
Managing saturation levels in shallow-water impoundments to resemble the seasonal variations in beaver pool and marsh systems can create lush growth and wildlife-rich environments. Take a look at some images from a project in a headwaters area of a tributary to Conewago Creek (west)…
By late July, southbound shorebirds were already using these mudflats to feed and rest. Other sections of the impoundment were dense with emergent and aquatic plants, the latter kept hydrated in deeper pools of the project by the inflow from several captured springs that supplement direct rainfall and sheet runoff to supply its water. During a seasonal drawdown, the exposure of the impoundment’s soils to direct sunlight can provide a measure of disinfection to reduce the chances of disease transmission among its populations of visiting birds and other animals.In the deeper pools of the impoundment, water lilies and other aquatic plants grow in lush mats to provide cover and feeding areas for resident populations of breeding reptiles and amphibians.An abundance of foods are available for waders including this Green Heron……and this immature Little Blue Heron, a wanderer typical of more southern latitudes.While walking the road among tall grasses in the supporting landscape surrounding this impoundment, we were at first startled when these Sandhill Cranes strode by going the other direction. We quietly kept moving,……then spotted them again as we looked across the impoundment to realize they weren’t alone, but were escorting a colt.The hatching of this colt is testimony to the vital role wetland ecosystems play in the lives of hundreds of species. Whether they be beaver pools and marshes on lotic waters or man-made shallow lentic waters, each of these habitats is filling a void that left floodplains and other critical lowland biomes faltering. While they can’t replace the full-function floodplain management provided by an active beaver colony, shallow-water impoundments can provide relief for habitat-starved populations of the animals and plants that rely upon them. A constellation of these projects on lands public or private across the lower Susquehanna watershed could help provide refuge for many of our flora and fauna with the most desperately fragmented of ranges.
So that you can relax while observing the comings and goings at a pair of the lower Susquehanna valley’s man-made impoundments, the Pennsylvania Game Commission has erected two viewing pavilions for public use on its lands…
The Haldeman Island observation pavilion is located on State Game Lands 290 just upstream from the Juniata River’s mouth on the Susquehanna at Clark’s Ferry in Dauphin County.It overlooks not only the island’s man-made shallow-water impoundments and neighboring grasslands, but the tower used in the 1970s to reintroduce Bald Eagles from Saskatchewan to the lower Susquehanna. Interpretive signs explain the conservation stories of habitats and the eagle reintroduction program.The observation pavilion at Middle Creek Wildlife Management Area is of similar construction to the one at Haldeman Island. It is accessed from the parking pull-off along the tour road at its intersection with Chapel Road, just before the right turn and incline that leads to the “Stop 3” grassland overlook.It too includes numerous interpretive signs to help visitors understand impoundment management.
During the next two weeks, the exodus of migrating shorebirds now staged and feeding upon Atlantic Horseshoe Crab eggs on Delaware Bay will commence. During the evening of their departure from the bay, many of these birds cross portions of the Lower Susquehanna River Watershed, particularly east of the river. Stormy weather and other climatic conditions may force some of them to seek a place to put down temporarily, so keeping a close eye on the new pothole-like impoundment at Middle Creek may be a prudent move. After that, waders known as “post-breeding wanderers” can show up at any time. Then, beginning as early as late June, shorebirds begin moving south on a migration that can provide us with viewing opportunities into September and beyond. See you out there!
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.Migrating American Robins are still transiting region, but an abundance of wild fruits can prompt hundreds to linger through winter. Look for them near supplies of wild grape, Poison Ivy, dogwood, Virginia Creeper, hackberry, hawthorn, American Holly,……Eastern Red Cedar,……and Common Winterberry.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.
Back for an afternoon visit on a limb above the pond, our surprise guest seems to find our dining experience irresistible. During recent winters, the Green Frogs in the headquarters habitat have continued to be active through at least New Year’s Day. If it appears we’re going to have a Red-shouldered Hawk lingering that long, perhaps we’ll be motivated to clean our windows so we might get an even better look.
Earlier this morning, we photographed this adult Red-shouldered Hawk as it took a break from its southbound journey to eye up the Green Frogs in the susquehannawildlife.net headquarters pond. Hunger must surely outweigh timidity because this bird persisted in its hunt despite the activity of a crew of contractors noisily grinding up asphalt in the street just 40 feet away!
It begins on a sunny morning in spring each year, just as the ground temperature reaches sixty degrees or more…
Eastern Subterranean Termites emerge in unison from a nest located in the soil beneath a log. Each of these swarming “alates” is a potential king or queen seeking to find a location with an ample supply of fallen timber to provide food for establishment of a new colony. They are escorted to the surface by a soldier (lower center) equipped with powerful jaws for protecting the existing nest. Similar-looking worker termites tend the nest, the queen, her eggs, and their siblings, but usually remain hidden from view. The workers feed upon wood, hosting cellulose-digesting protozoa and bacteria in their guts to break down the fibers. This symbiotic relationship is an important mode of decomposition in the forest, the process that turns wood into the organic matter that enriches soil and helps it to retain more moisture.Termites are among the numerous arthropods that join fungi and a variety of microbes to decompose dead wood and other plant matter into the nutrients and organic materials used by living plants to thrive and grow.Within moments of emerging, swarming “alates” ascend a tree trunk or other vertical surface from which they can take flight.Eastern Subterranean Termite “alates” gather atop a stump before launching skyward.Termites swarm in massive numbers in an attempt to overwhelm the predators that are inevitably attracted to their sudden appearance. The few “alates” that survive to find a source of rotting wood in which to begin a new colony are the only hope for continuing their king and queen’s legacy.Soon after lift off, the majority of swarming termites are consumed by swallows, swifts, and other birds, but some are discovered at ground level.A lightning-fast strike with its tongue and this Green frog has snatched up yet another termite. Those that slip by the dragnet of terrestrial and aerial predators can sometimes start a new colony in the ground beneath a dead tree or in a vulnerable house or other wooden structure. To keep a small clan from invading your home, be certain the wood elements of your building(s) are kept dry and are not in contact with dirt, soil, bark mulch, etc. Regular inspections for evidence of their presence can head off the long-term damage termites can inflict on the stuff we construct with tree skeletons.A Green Frog wearing its breakfast. Its next chance for a termite feast may come during the autumn when the Drywood Termites (Kalotermitidae) swarm.
Of course, termites aren’t the only groups of insects to swarm. As heated runoff from slow-moving thundershowers has increased stream temperatures during the past couple of weeks, there have occurred a number of seasonal mayfly “hatches” on the Susquehanna and its tributaries. These “hatches” are actually the nuptial flights of newly emerged imago and adult mayflies. The most conspicuous of these is the Great Brown Drake.
Seen here with a much smaller and more typical regional mayfly to its left, the Great Brown Drake was for several years infamous for swarming the lights and creating traffic hazards on bridges spanning the Susquehanna. During the past two weeks, nighttime flights of these giants have ventured out to gather at well lit locations in housing and business districts more than a dozen miles from the river. Earlier this century, this proclivity to wander probably led the Great Brown Drake to first invade silty segments of the Susquehanna as a colonizer from its native range in the Mississippi watershed.
Swarms of another storm-related visitor are being seen throughout the lower Susquehanna valley right now. Have you noticed the Wandering Gliders?
Throughout the month, swarms of Wandering Gliders, the most widespread dragonflies in the world, descended on areas hit by localized slow-moving thundershowers. Large numbers of these global travelers are known to get swept up within the thermal air masses that lead to these storms. In suitable terrain within the path of the downpours, they linger to search for flooded places where they can mate and deposit eggs. Wandering Gliders frequently mistake large parking lots at shopping malls, grocery stores, etc. for wetlands and will be seen in these areas depositing eggs upon the hoods and roofs of shiny motor vehicles, surfaces which appear puddle-like in their eyes.More dragonfly swarms are yet to come. Adult Common Green Darners are presently in the Lower Susquehanna River Watershed mating and depositing eggs within vegetated ponds, lakes, and wetlands. Beginning in August, adult Common Green Darners and other migratory species including Black Saddlebags, Carolina Saddlebags, Wandering Gliders, and Twelve-spotted Skimmers will begin swarming as they feed on flying insects (including lots of mosquitos and gnats) and start working their way toward the Atlantic Coastal Plain. Along the barrier islands by September, concentrations of southbound dragonflies can reach the thousands, particularly at choke points like Cape May, New Jersey, and Cape Charles, Virginia. So be sure to keep an eye on the sky for swarms of dragonflies during coming weeks. And don’t forget to check out our “Damselflies and Dragonflies” page by clicking the tab at the top of this page.
2025 begins as the fourth consecutive New Year’s Day with the Green Frogs out and about in the water garden at susquehannawildlife.net headquarters. As colder weather arrives during the next 48 hours, these native amphibians will retreat to the bottom of the ponds and become motionless. The breathing of atmospheric air through their lungs will cease and they will instead exchange oxygen and carbon dioxide by diffusion through their skin. During this time, the pond must not freeze all the way to the bottom and dissolved oxygen levels in the water beneath the ice must remain sufficient to support the hibernating frogs and other life.
Among the Green Frogs in the ponds at susquehannawildlife.net headquarters, a specific recessive allele is present among the population of these native amphibians. On occasions when male and female carriers of this particular recessive allele get together to produce offspring, about one quarter of the progeny will receive a copy of this mutated version of a gene from each parent. The rare recipient of this pair of recessive alleles that happens to survive the process of hatching from its egg and metamorphosing through the tadpole stage to adulthood will reveal the uncommon appearance of an amphibian with the condition resulting from this inheritance—axanthism.
Axanthic Green Frogs and other amphibians do not produce yellow pigment, therefore the normally yellow surfaces of their bodies appear white, the green surfaces blue. Axanthism is expressed only in individuals possessing a pair of specific recessive alleles for a gene that affects the cells that produce the yellow pigment. For the trait to be expressed, a frog must receive one copy of the recessive allele from each parent.The last axanthic Green Frog we saw in the headquarters ponds was this male (seen here with a typical male Green Frog) found back in July, 2008. Green Frogs that receive two copies of a dominant allele or a copy of a dominant and a recessive allele from their parents will not express the recessive trait for the axanthism gene. Making observation of cases of axanthism even rarer is the fact that blue coloration can make these frogs exceptionally susceptible to predation. Few live long enough to reproduce and thus increase the occurrence of the mutation in a population of frogs*. This cyanic individual was present during a time when “outdoor” Domestic Cats were killing frogs to take home to their misguided humans. After this brief sighting and single photograph, this blue Green Frog was never seen again.
*The incidence of axanthic frogs can increase when a blue parent, which has a pair of the recessive alleles and is therefore said to be homozygous recessive, mates with a typical-looking frog that carries both a dominant and a recessive allele for the axanthism gene and is therefore said to be heterozygous. Approximately 50% of the young from this pairing will express axanthism. By comparison, a pair of frogs that are both heterozygous will produce 25% axanthic young, and a pair of frogs that are both blue (homozygous) will yield 100% axanthic young. A pair of frogs that includes an individual that is herterozygous and a mate that is homozygous dominant for the gene will produce no axanthic frogs, but 50% of the young will be carriers of the recessive allele. A pair of homozygous dominant frogs produces no axanthic young and no carriers of the recessive allele.
It’s been a green Christmas at susquehannawildlife.net headquarters. Among thick growth of Lesser Duckweed and other aquatic plants in the garden ponds, the Green Frogs and their tadpoles remain active. The water’s open…still no ice here.
When you were young, you may have selected your tennis shoes because they promised to make you run faster and jump higher. Remember those? Then as you got a bit older, you may have really wanted the brand that would get you noticed—those overpriced status-symbol athletic shoes. As the years went by and you put on the extra pounds in all the wrong places, maybe it occurred to you that it might be a really good idea to get some exercise. So you went out and bought some stylish and expensive fitness footwear that promised to help you run faster and jump higher—and wore that pair to go shopping at the grocery store. Then you finally realized…
…that the best sneakers are just something comfortable to loaf around in.Wisdom does come with age.
Flies? Cabbage White butterflies? Can it really be a late-February day? It certainly is. Here are a few more signs of an early spring.
Green Frogs were out and about on this balmy February day trying to latch on to one of those flying insects. Their long winter’s nap lasted just over six weeks.Approximately two hundred Common Grackles passed by susquehannawildlife.net headquarters today. This one stopped to have a look around before continuing its northbound expedition.Difficult to spot, hundreds of high-flying Canada Geese were seen in the hazy sky above the headquarters garden during the late morning. These migrants are working their way north from Chesapeake Bay and won’t be seen again in our region until fall.
Following the deep freeze of a week ago, temperatures soaring into the fifties and sixties during recent days have brought to mind thoughts of spring. In the pond at susquehannawildlife.net headquarters, Green Frogs are again out and about.
A pair of Green Frogs seen today alongside the headquarters pond. A sign of spring?
But is this really an early spring? Migrating waterfowl indicate otherwise. Having been forced south from the Great Lakes during the bitter cold snap, a variety of our tardy web-footed friends belatedly arrived on the river and on the Susquehanna Flats of upper Chesapeake Bay about ten days ago. Now, rising water from snow melt and this week’s rains have forced many of these ducks onto local lakes and ponds where ice coverage has been all but eliminated by the mild weather. For the most part, these are lingering autumn migrants. Here’s a sample of some of the waterfowl seen during a tour of the area today…
Like other late-season migrants, Snow Geese take advantage of open water on area lakes until ice forces them south to the Atlantic Coastal Plain. In a little more than a month from now, they’ll begin working their way north again.Tundra Swans and American Black Ducks loafing on an ice-free lake.The non-native Mute Swan has become an invasive species. Because they are predominantly non-migratory, groups of Mute Swans congregating in valuable wetland habitat can decimate these aquatic ecosystems with their persistent year-round feeding. Their long necks help them consume enormous quantities of benthic foods that would otherwise be available to migratory diving ducks during their autumn and spring stopovers.Small flocks of Gadwalls will sometimes spend the winter on ice-free vegetated ponds in the lower Susquehanna region.A mixed flock of diving ducks on a small lake. Let’s take a closer look!Six Redheads, three Lesser Scaup (top row left), and a Canvasback (upper right).Redheads.Buffleheads.An adult male Lesser Scaup.A female (right) and a first-winter male (left) Lesser Scaup.Canvasbacks and a Ruddy Duck.
With the worst of winter’s fury still to come, it’s time to say farewell to most of these travelers for a little while. With a little luck, we’ll see them again in March or April.
Our official susquehannawildlife.net prognosticator climbed out of its winter hideout today to have a look around. Then, without hesitation, the forecast for 2023 was issued, “Winter Stinks!”
A bit on the mild side for the final days of December, wouldn’t you say? This Green Frog living in the pond at the susquehannawildlife.net headquarters certainly thinks so.
The mild winter has apparently minimized weather-related mortality for the local Green Frog population. With temperatures in the seventies throughout the lower Susquehanna valley for this first full day of spring, many recently emerged adults could be seen and, on occasion, heard. Yellow-throated males tested their mating calls—reminding the listener of the sound made by the plucking of a loose banjo string.
Here’s a gathering of Green Frogs seen this afternoon along the edge of a small pond. How many can you find in this photograph?
If you venture out, keep alert for the migrating birds of late winter and early spring.
Yellow-bellied Sapsuckers are moving through on their way north. Look for them in mature trees in woodlands, suburbs, and city parks.The Fox Sparrow (Passerella iliaca), our largest sparrow, is a thrush-like denizen of shrubby forest understories and field edges. It is an early spring and late autumn transient in the lower Susquehanna valley.While stopping to rest and feed during their northbound spring journey, Ring-necked Ducks and other diving duck species visit wetlands and flooded timber along the Susquehanna River as well as clear ponds and lakes elsewhere in the watershed.Eastern Bluebirds are presently migrating through the area. Some will stay to breed where nest boxes or natural cavities are available in suitable habitat.Tree Swallows are now arriving. In open grasslands, pastures, and adjacent to almost any body of water, they will nest in boxes like those placed for bluebirds.Keep that bird bath clean and fill it with fresh water, the American Robin flights are peaking right now. Breeding males like this one are starting to sing and defend nesting territories.Red-winged Blackbirds, like other native blackbirds, are moving through in a fraction of the numbers that were seen in the lower Susquehanna valley during the latter decades of the twentieth century. They remain a common breeding species in pastures and cattail wetlands.And of course, keep an eye to the sky. There are still thousands of Snow Geese in the area.
If you’re staying close to home, be sure to check out the changing appearance of the birds you see nearby. Some species are losing their drab winter basic plumage and attaining a more colorful summer breeding alternate plumage.
European Starlings are losing their spotted winter (basic) plumage and beginning to display a glossy multicolored set of breeding feathers.An American Goldfinch in transition from winter (basic) plumage to bright yellow, black, and white summer colors.
So just how many Green Frogs were there in that first photograph? Here’s the answer.
If you counted seven, you did really well. Numbers eight and nine are very difficult to discern.
Happy Spring. For the benefit of everyone’s health, let’s hope that it’s a hot and humid one!
Inside the doorway that leads to your editor’s 3,500 square foot garden hangs a small chalkboard upon which he records the common names of the species of birds that are seen there—or from there—during the year. If he remembers to, he records the date when the species was first seen during that particular year. On New Year’s Day, the results from the freshly ended year are transcribed onto a sheet of notebook paper. On the reverse, the names of butterflies, mammals, and other animals that visited the garden are copied from a second chalkboard that hangs nearby. The piece of paper is then inserted into a folder to join those from previous New Year’s Days. The folder then gets placed back into the editor’s desk drawer beneath a circular saw blade and an old scratched up set of sunglasses—so that he knows exactly where to find it if he wishes to.
A quick glance at this year’s list calls to mind a few recollections.
The 2019 bird list included 48 species, the 47 on the board plus Ruby-throated Hummingbird, which was logged on a slip of paper found tucked into the edge of the frame.
This Green Frog, photographed on New Year’s Day 2019, was “out and about” along the edge of the editor’s garden pond. Due to the recent mild weather, Green Frogs were active during the current New Year’s holiday as well.On a day with strong south winds in late February or during the first two weeks of March, there is often a conspicuous northbound spring flight of migrating waterfowl, gulls, and songbirds that crosses the lower Susquehanna valley as it departs Chesapeake Bay. These Tundra Swans were among the three thousand seen from the garden patio on March 13, 2019. A thousand migrating Canada Geese, 500 Red-winged Blackbirds, numerous Ring-billed Gulls, and some American Herring Gulls were seen during the same afternoon.This juvenile Cooper’s Hawk was photographed through the editor’s kitchen window. From its favorite perch on this arbor it would occasionally find success snagging a House Sparrow from the large local flock. It first visited the garden in November, the species being absent there since early spring. Unlike previous years, there was no evidence of a breeding pair in the vicinity during 2019.Plantings that provide food and cover for wildlife are essential to their survival. Native flowers including Trumpet Vine (Campsis radicans) and Partridge Pea provide nourishment for the Ruby-throated Hummingbirds that visit the editor’s garden, but they really love a basket or pot filled with Mexican Cigar (Cuphea ignea) too. The latter (seen here) can be grown as a houseplant and moved outdoors to a semi-shaded location in summer and early fall. But remember, it’s tropical, so you’ll need to bring it back inside when frost threatens.A Swamp Sparrow is an unusual visitor to a small property surrounded by paved parking lots and treeless lawns. Nevertheless, aquatic gardens and native plants helped to attract this nocturnal migrant, seen here eating seeds from Indiangrass. It arrived on September 30 and was gone on October 2.
Before putting the folder back into the drawer for another year, the editor decided to count up the species totals on each of the sheets and load them into the chart maker in the computer.
Despite the habitat improvements in the garden, the trend is apparent. Bird diversity has not cracked the 50 species mark in 6 years. Despite native host plants and nectar species in abundance, butterfly diversity has not exceeded 10 species in 6 years.
It appears that, at the very least, the garden habitat has been disconnected from the home ranges of many species by fragmentation. His little oasis is now isolated in a landscape that becomes increasingly hostile to native wildlife with each passing year. The paving of more parking areas, the elimination of trees, shrubs, and herbaceous growth from the large number of rental properties in the area, the alteration of the biology of the nearby stream by hand-fed domestic ducks, light pollution, and the outdoor use of pesticides have all contributed to the separation of the editor’s tiny sanctuary from the travel lanes and core habitats of many of the species that formerly visited, fed, or bred there. In 2019, migrants, particularly “fly-overs”, were nearly the only sightings aside from several woodpeckers, invasive House Sparrows (Passer domesticus), and hardy Mourning Doves. Even rascally European Starlings became sporadic in occurrence—imagine that! It was the most lackluster year in memory.
The Tufted Titmouse was a daily visitor to the garden through 2018. This one was photographed investigating holes in an old magnolia there during the spring of that year. There were no Tufted Titmouse sightings in the garden in 2019. This and other resident species, especially cavity nesters, appear to be experiencing at least a temporary decline.Breeding birds including Northern Cardinals may have had a difficult year. In the editor’s garden, a pair were still feeding and escorting one of their young in early October. The infestation of the editor’s town by domestic house and feral cats may have contributed to the failure of earlier broods, but a lack of food is also a likely factor.
If habitat fragmentation were the sole cause for the downward trend in numbers and species, it would be disappointing, but comprehensible. There would be no cause for greater alarm. It would be a matter of cause and effect. But the problem is more widespread.
Although the editor spent a great deal of time in the garden this year, he was also out and about, traveling hundreds of miles per week through lands on both the east and the west shores of the lower Susquehanna. And on each journey, the number of birds seen could be counted on fingers and toes. A decade earlier, there were thousands of birds in these same locations, particularly during the late summer.
At about the time of summer solstice in June each year, Common Grackles begin congregating into roving summer flocks that will grow in size to assure their survival during the autumn migration, winter season, and return north in the spring. From his garden, the editor saw just one flock of less than a dozen birds during the summer of 2019. He saw none during his journeys through other areas of the Susquehanna valley. Flocks of one hundred birds or more did not materialize until the southbound movements of grackles passed through the region in October and November.
In the lower Susquehanna valley, something has drastically reduced the population of birds during breeding season, post-breeding dispersal, and the staging period preceding autumn migration. In much of the region, their late-spring through summer absence was, in 2019, conspicuous. What happened to the tens of thousands of swallows that used to gather on wires along rural roads in August and September before moving south? The groups of dozens of Eastern Kingbirds (Tyrannus tyrannus) that did their fly-catching from perches in willows alongside meadows and shorelines—where are they?
Several studies published during the autumn of 2019 have documented and/or predicted losses in bird populations in the eastern half of the United States and elsewhere. These studies looked at data samples collected during recent decades to either arrive at conclusions or project future trends. They cite climate change, the feline infestation, and habitat loss/degradation among the factors contributing to alterations in range, migration, and overall numbers.
There’s not much need for analysis to determine if bird numbers have plummeted in certain Lower Susquehanna Watershed habitats during the aforementioned seasons—the birds are gone. None of these studies documented or forecast such an abrupt decline. Is there a mysterious cause for the loss of the valley’s birds? Did they die off? Is there a disease or chemical killing them or inhibiting their reproduction? Is it global warming? Is it Three Mile Island? Is it plastic straws, wind turbines, or vehicle traffic?
The answer might not be so cryptic. It might be right before our eyes. And we’ll explore it during 2020.
A clean slate for 2020.
In the meantime, Uncle Ty and I going to the Pennsylvania Farm Show in Harrisburg. You should go too. They have lots of food there.
