Grasshoppers are perhaps best known for the occasions throughout history when an enormous congregation of these insects—a “plague of locusts”—would assemble and rove a region to feed. These swarms, which sometimes covered tens of thousands of square miles or more, often decimated crops, darkened the sky, and, on occasion, resulted in catastrophic famine among human settlements in various parts of the world.
The largest “plague of locusts” in the United States occurred during the mid-1870s in the Great Plains. The Rocky Mountain Locust (Melanoplus spretus), a grasshopper of prairies in the American west, had a range that extended east into New England, possibly settling there on lands cleared for farming. Rocky Mountain Locusts, aside from their native habitat on grasslands, apparently thrived on fields planted with warm-season crops. Like most grasshoppers, they fed and developed most vigorously during periods of dry, hot weather. With plenty of vegetative matter to consume during periods of scorching temperatures, the stage was set for populations of these insects to explode in agricultural areas, then take wing in search of more forage. Plagues struck parts of northern New England as early as the mid-1700s and were numerous in various states in the Great Plains through the middle of the 1800s. The big ones hit between 1873 and 1877 when swarms numbering as many as trillions of grasshoppers did $200 million in crop damage and caused a famine so severe that many farmers abandoned the westward migration. To prevent recurrent outbreaks of locust plagues and famine, experts suggested planting more cool-season grains like winter wheat, a crop which could mature and be harvested before the grasshoppers had a chance to cause any significant damage. In the years that followed, and as prairies gave way to the expansive agricultural lands that presently cover most of the Rocky Mountain Locust’s former range, the grasshopper began to disappear. By the early years of the twentieth century, the species was extinct. No one was quite certain why, and the precise cause is still a topic of debate to this day. Conversion of nearly all of its native habitat to cropland and grazing acreage seems to be the most likely culprit.
In the Mid-Atlantic States, the mosaic of the landscape—farmland interspersed with a mix of forest and disturbed urban/suburban lots—prevents grasshoppers from reaching the densities from which swarms arise. In the years since the implementation of “Green Revolution” farming practices, numbers of grasshoppers in our region have declined. Systemic insecticides including neonicotinoids keep grasshoppers and other insects from munching on warm-season crops like corn and soybeans. And herbicides including 2,4-D (2,4-Dichlorophenoxyacetic acid) have, in effect, become the equivalent of insecticides, eliminating broadleaf food plants from the pasturelands and hayfields where grasshoppers once fed and reproduced in abundance. As a result, few of the approximately three dozen species of grasshoppers with ranges that include the Lower Susquehanna River Watershed are common here. Those that still thrive are largely adapted to roadsides, waste ground, and small clearings where native and some non-native plants make up their diet.
Here’s a look at four species of grasshoppers you’re likely to find in disturbed habitats throughout our region. Each remains common in relatively pesticide-free spaces with stands of dense grasses and broadleaf plants nearby.
Protein-rich grasshoppers are an important late-summer, early-fall food source for birds. The absence of these insects has forced many species of breeding birds to abandon farmland or, in some cases, disappear altogether.
To pass the afternoon, we sat quietly along the edge of a pond created recently by North American Beavers (Castor canadensis). They first constructed their dam on this small stream about five years ago. Since then, a flourishing wetland has become established. Have a look.
Isn’t that amazing? North American Beavers build and maintain what human engineers struggle to master—dams and ponds that reduce pollution, allow fish passage, and support self-sustaining ecosystems. Want to clean up the streams and floodplains of your local watershed? Let the beavers do the job!
At Lake Redman just to the south of York, Pennsylvania, a draw down to provide drinking water to the city while maintenance is being performed on the dam at neighboring Lake Williams, York’s primary water source, has fortuitously coincided with autumn shorebird migration. Here’s a sample of the numerous sandpipers and plovers seen today on the mudflats that have been exposed at the southeast end of the lake…
Not photographed but present at Lake Redman were at least two additional species of shorebirds, Killdeer and Spotted Sandpiper—bringing the day’s tally to ten. Not bad for an inland location! It’s clearly evident that these waders overfly the lower Susquehanna valley in great numbers during migration and are in urgent need of undisturbed habitat for making stopovers to feed and rest so that they might improve their chances of surviving the long journey ahead of them. Mud is indeed a much needed refuge.
Your best bet for finding migrating shorebirds in the lower Susquehanna region is certainly a visit to a sandbar or mudflat in the river. The Conejohela Flats off Washington Boro just south of Columbia is a renowned location. Some man-made lakes including the one at Middle Creek Wildlife Management Area are purposely drawn down during the weeks of fall migration to provide exposed mud and silt for feeding and resting sandpipers and plovers. But with the Susquehanna running high due to recent rains and the cost of fuel trending high as well, maybe you want to stay closer to home to do your observing.
Fortunately for us, migratory shorebirds will drop in on almost any biologically active pool of shallow water and mud that they happen to find. This includes flooded portions of fields, construction sites, and especially stormwater retention basins. We stopped by a new basin just west of Hershey, Pennsylvania, and found more than two dozen shorebirds feeding and loafing there. We took each of these photographs from the sidewalk paralleling the south shore of the pool, thus never flushing or disturbing a single bird.
So don’t just drive by those big puddles, stop and have a look. You never know what you might find.
Have you purchased your 2023-2024 Federal Duck Stamp? Nearly every penny of the 25 dollars you spend for a duck stamp goes toward habitat acquisition and improvements for waterfowl and the hundreds of other animal species that use wetlands for breeding, feeding, and as migration stopover points. Duck stamps aren’t just for hunters, purchasers get free admission to National Wildlife Refuges all over the United States. So do something good for conservation—stop by your local post office and get your Federal Duck Stamp.
Still not convinced that a Federal Duck Stamp is worth the money? Well then, follow along as we take a photo tour of Bombay Hook National Wildlife Refuge. Numbers of southbound shorebirds are on the rise in the refuge’s saltwater marshes and freshwater pools, so we timed a visit earlier this week to coincide with a late-morning high tide.
As the tide recedes, shorebirds leave the freshwater pools to begin feeding on the vast mudflats exposed within the saltwater marshes. Most birds are far from view, but that won’t stop a dedicated observer from finding other spectacular creatures on the bay side of the tour route road.
No visit to Bombay Hook is complete without at least a quick loop through the upland habitats at the far end of the tour route.
We hope you’ve been convinced to visit Bombay Hook National Wildlife Refuge sometime soon. And we hope too that you’ll help fund additional conservation acquisitions and improvements by visiting your local post office and buying a Federal Duck Stamp.
Visitors stopping by Middle Creek Wildlife Management Area this week found yet another post-breeding wanderer feeding in the shallows of the main lake and adjacent pond along Hopeland Road—a juvenile Little Blue Heron.
The juvenile Little Blue Heron is a white bird resembling an egret during its first year. At about one year of age, it begins molt into a deep blue adult plumage. Young birds are notorious for roaming inland and north from breeding areas along the Atlantic coast and throughout the south. They are a post-breeding wanderer nowhere near as rare as the Limpkin seen at Middle Creek a week ago; a few are found each summer in the Lower Susquehanna River Watershed.
As oft times happens, birders attracted to see one unusual bird find another in the vicinity. So with fall shorebird migration ramping up, the discovery of something out of the ordinary isn’t a total surprise, particularly where habitat is good and people are watching.
The arrival of a Hudsonian Godwit is not an unheard of occurrence in the lower Susquehanna region, but locating one that sticks around and provides abundant viewing opportunities is a rarity. This adult presumably left the species’ breeding areas in Alaska or central/western Canada in recent weeks to begin its southbound movement. Hudsonian Godwits pass through the eastern United States only during the autumn migration, and the majority fly by without being noticed along a route that mostly takes them offshore of the Mid-Atlantic States.
Mid-summer can be a less than exciting time for those who like to observe wild birds. The songs of spring gradually grow silent as young birds leave the nest and preoccupy their parents with the chore of gathering enough food to satisfy their ballooning appetites. To avoid predators, roving families of many species remain hidden and as inconspicuous as possible while the young birds learn how to find food and handle the dangers of the world.
But all is not lost. There are two opportunities for seeing unique birds during the hot and humid days of July.
First, many shorebirds such as sandpipers, plovers, dowitchers, and godwits begin moving south from breeding grounds in Canada. That’s right, fall migration starts during the first days of summer, right where spring migration left off. The earliest arrivals are primarily birds that for one reason on another (age, weather, food availability) did not nest this year. These individuals will be followed by birds that completed their breeding cycles early or experienced nest failures. Finally, adults and juveniles from successful nests are on their way to the wintering grounds, extending the movement into the months we more traditionally start to associate with fall migration—late August into October.
For those of you who find identifying shorebirds more of a labor than a pleasure, I get it. For you, July can bring a special treat—post-breeding wanderers. Post-breeding wanderers are birds we find roaming in directions other than south during the summer months, after the nesting cycle is complete. This behavior is known as “post-breeding dispersal”. Even though we often have no way of telling for sure that a wandering bird did indeed begin its roving journey after either being a parent or a fledgling during the preceding nesting season, the term post-breeding wanderer still applies. It’s a title based more on a bird sighting and it’s time and place than upon the life cycle of the bird(s) being observed. Post-breeding wanderers are often southern species that show up hundreds of miles outside there usual range, sometimes traveling in groups and lingering in an adopted area until the cooler weather of fall finally prompts them to go back home. Many are birds associated with aquatic habitats such as shores, marshes, and rivers, so water levels and their impact on the birds’ food supplies within their home range may be the motivation for some of these movements. What makes post-breeding wanderers a favorite among many birders is their pop. They are often some of our largest, most colorful, or most sought-after species. Birds such as herons, egrets, ibises, spoonbills, stilts, avocets, terns, and raptors are showy and attract a crowd.
While it’s often impossible to predict exactly which species, if any, will disperse from their typical breeding range in a significant way during a given year, some seem to roam with regularity. Perhaps the most consistent and certainly the earliest post-breeding wanderer to visit our region is the “Florida Bald Eagle”. Bald Eagles nest in “The Sunshine State” beginning in the fall, so by early spring, many of their young are on their own. By mid-spring, many of these eagles begin cruising north, some passing into the lower Susquehanna valley and beyond. Gatherings of dozens of adult Bald Eagles at Conowingo Dam during April and May, while our local adults are nesting and after the wintering birds have gone north, probably include numerous post-breeding wanderers from Florida and other Gulf Coast States.
So this week, what exactly was it that prompted hundreds of birders to travel to Middle Creek Wildlife Management Area from all over the Mid-Atlantic States and from as far away as Colorado?
Was it the majestic Great Blue Herons and playful Killdeer?
Was it the colorful Green Herons?
Was it the Great Egrets snapping small fish from the shallows?
Was it the small flocks of shorebirds like these Least Sandpipers beginning to trickle south from Canada?
All very nice, but not the inspiration for traveling hundreds or even thousands of miles to see a bird.
It was the appearance of this very rare post-breeding wanderer…
…Pennsylvania’s first record of a Limpkin, a tropical wading bird native to Florida, the Caribbean Islands, and South America. Many observers visiting Middle Creek Wildlife Management Area had never seen one before, so if they happen to be a “lister”, a birder who keeps a tally of the wild bird species they’ve seen, this Limpkin was a “lifer”.
The Limpkin is an inhabitant of vegetated marshlands where it feeds almost exclusively upon large snails of the family Ampullariidae, including the Florida Applesnail (Pomacea paludosa), the largest native freshwater snail in the United States.
Observations of the Limpkin lingering at Middle Creek Wildlife Management Area have revealed a pair of interesting facts. First, in the absence of Florida Applesnails, this particular Limpkin has found a substitute food source, the non-native Chinese Mystery Snail (Cipangopaludina chinensis). And second, Chinese Mystery Snails have recently become established in the lakes, pools, and ponds at the refuge, very likely arriving as stowaways on Spatterdock (Nupharadvena) and/or American Lotus (Nelumbo lutea), native transplants brought in during recent years to improve wetland habitat and process the abundance of nutrients (including waterfowl waste) in the water.
The Middle Creek Limpkin’s affinity for Chinese Mystery Snails may help explain how it was able to find its way to Pennsylvania in apparent good health. Look again at the map showing the range of the Limpkin’s primary native food source, the Florida Applesnail. Note that there are established populations (shown in brown) where these snails were introduced along the northern coast of Georgia and southern coast of South Carolina…
…now look at the latest U.S.G.S. Nonindigenous Aquatic Species map showing the ranges (in brown) of established populations of non-native Chinese Mystery Snails…
…and now imagine that you’re a happy-go-lucky Limpkin working your way up the Atlantic Coastal Plain toward Pennsylvania and taking advantage of the abundance of food and sunshine that summer brings to the northern latitudes. It’s a new frontier. Introduced populations of Chinese Mystery Snails are like having a Waffle House serving escargot at every exit along the way!
Be sure to click the “Freshwater Snails” tab at the top of this page to learn more about the Chinese Mystery Snail and its arrival in the Lower Susquehanna River Watershed. Once there, you’ll find some additional commentary about the Limpkin and the likelihood of Everglade Snail Kites taking advantage of the presence of Chinese Mystery Snails to wander north. Be certain to check it out.
It’s been more than a year and a half since Uncle Tyler Dyer has been on one of our outings. He’s been laying low, keeping to himself—to protect his health. So he was quite excited when we made our way to the Delaware coast to have a look at some marine and beach life at Cape Henlopen State Park.
Uncle Ty hadn’t visited the Atlantic shoreline here for almost two decades, and he was more than a bit startled at what he saw…
A nearly sterile beach might be delightful for barefoot sunbathers and the running of the dogs, but Uncle Ty isn’t the barefoot type. He likes his sandals and a slow peaceful stroll with plenty of flora and fauna to have a look at. We could tell he was getting bored. So we headed home.
Along the way, Uncle Ty asked to stop at the Post Office. He wanted to get a stamp. Thinking he was going to fire off a terse letter of protest to the powers that be about what he saw at the beach, we obliged.
Soon, Uncle Ty trotted down the steps of the Post Office with his stamp.
Uncle Ty bought a duck stamp, so naturally we asked him when he decided to take up hunting. He explained, “Man, I gave that stuff up when I was thirteen. I’ve got the Thoreau/Walden mindset—hunting is something of an adolescent pursuit.”
It turns out Uncle Ty bought a duck stamp to support wetland acquisition and improvements, not only to benefit ducks and other wildlife living there, but to improve water quality. In Delaware, tidal estuary restoration work is underway at both the Prime Hook and Bombay Hook National Wildlife Refuges on Delaware Bay. These projects will certainly enhance the salt marsh’s filtration capabilities and just might improve the populations of benthic life in the bay and adjacent ocean at Cape Henlopen.
Uncle Ty tossed the stamp atop the dashboard and we were again on our way, but we weren’t going directly home. We made a stop along the way. A stop we’ll share with you next time.
Late August and early September is prime time to see migrating shorebirds as they pass through the lower Susquehanna valley during their autumn migration, which, believe it or not, can begin as early as late June. These species that are often assumed to spend their lives only near the seashore are regular visitors each fall as they make their way from breeding grounds in the interior of Canada to wintering sites in seacoast wetlands—many traveling as far south as Central and South America.
Low water levels on the Susquehanna River often coincide with the shorebird migration each year, exposing gravel and sand bars as well as vast expanses of muddy shorelines as feeding and resting areas for these traveling birds. This week though, rain from the remnants of Tropical Storm Fred arrived to increase the flow in the Susquehanna and inundate most of the natural habitat for shorebirds. Those on the move must either continue through the area without stopping or find alternate locations to loaf and find food.
The draining and filling of wetlands along the river and elsewhere in the region has left few naturally-occurring options. The Conejohela Flats south of Columbia offer refuge to many migrating sandpipers and their allies, the river level there being controlled by releases from the Safe Harbor Dam during all but the severest of floods. Shorebirds will sometimes visit flooded fields, but wide-open puddles and farmland resembling mudflats is more of springtime occurrence—preceding the planting and growth of crops. Well-designed stormwater holding facilities can function as habitat for sandpipers and other wildlife. They are worth checking on a regular basis—you never know what might drop in.
Right now, there is a new shorebird hot spot in the Lower Susquehanna River Watershed—Middle Creek Wildlife Management Area. The water level in the main impoundment there has been drawn down during recent weeks to expose mudflats along the periphery of nearly the entire lake. Viewing from “Stop 1” (the roadside section of the lake in front of the refuge museum) is best. The variety of species and their numbers can change throughout the day as birds filter in and out—at times traveling to other mudflats around the lake where they are hidden from view. The birds at “Stop 1” are backlit in the morning with favorable illumination developing in the afternoon.
Have a look at a few of the shorebirds currently being seen at Middle Creek…
The aquatic environs at Middle Creek attract other species as well. Here are some of the most photogenic…
You’ll want to go for a walk this week. It’s prime time to see birds in all their spring splendor. Colorful Neotropical migrants are moving through in waves to supplement the numerous temperate species that arrived earlier this spring to begin their nesting cycle. Here’s a sample of what you might find this week along a rail-trail, park path, or quiet country road near you—even on a rainy or breezy day.
After nearly a full week of record-breaking cold, including two nights with a widespread freeze, warm weather has returned. Today, for the first time this year, the temperature was above eighty degrees Fahrenheit throughout the lower Susquehanna region. Not only can the growing season now resume, but the northward movement of Neotropical birds can again take flight—much to our delight.
A rainy day on Friday, May 8, preceded the arrival of a cold arctic air mass in the eastern United States. It initiated a sustained layover for many migrating birds.
Freeze warnings were issued for five of the next six mornings. The nocturnal flights of migrating birds, most of them consisting of Neotropical species by now, appeared to be impacted. Even on clear moonlit nights, these birds wisely remained grounded. Unlike the more hardy species that moved north during the preceding weeks, Neotropical birds rely heavily on insects as a food source. For them, burning excessive energy by flying through cold air into areas that may be void of food upon arrival could be a death sentence. So they wait.
Today throughout the lower Susquehanna region, bird songs again fill the air and it seems to be mid-May as we remember it. The flights have resumed.
You need to get outside and go for a walk. You’ll be sorry if you don’t. It’s prime time to see wildlife in all its glory. The songs and colors of spring are upon us!
If you’re not up to a walk and you just want to go for a slow drive, why not take a trip to Middle Creek Wildlife Management Area and visit the managed grasslands on the north side of the refuge. To those of us over fifty, it’s a reminder of how Susquehanna valley farmlands were before the advent of high-intensity agriculture. Take a look at the birds found there right now.
And remember, if you happen to own land and aren’t growing crops on it, put it to good use. Mow less, live more. Mow less, more lives.
The NOAA National Weather Service radar images from last evening provided an indication that there may be a good fallout of birds at daybreak in the lower Susquehanna valley. The moon was bright, nearly full, and there was a gentle breeze from the north to move the nocturnal migrants along. The conditions were ideal.
The Riparian Woodlands at Conewago Falls were alive with migrants this morning. American Robins and White-throated Sparrows were joined by new arrivals for the season: Brown Creeper (Certhia americana), Ruby-crowned Kinglets (Regulus calendula), Golden-crowned Kinglets (Regulus satrapa), Dark-eyed Junco (Junco hyemalis), and Yellow-rumped Warbler (Setophaga coronata). These are the perching birds one would expect to have comprised the overnight flight. While the individuals that will remain may not yet be among them, these are the species we will see wintering in the Mid-Atlantic states. No trip to the tropics for these hardy passerines.
The humid rainy remains of Hurricane Nate have long since passed by Pennsylvania, yet mild wet weather lingers to confuse one’s sense of the seasons. This gloomy misty day was less than spectacular for watching migrating birds and insects, but some did pass by. Many resident animals of the falls are availing themselves of the opportunity to continue active behavior before the cold winds of autumn and winter force a change of lifestyle.
Warm drizzle at daybreak prompted several Northern Spring Peepers (Pseudacris crucifer crucifer) to begin calling from the wetlands in the Riparian Woodlands of Conewago Falls. An enormous chorus of these calls normally begins with the first warm rains of early spring to usher in this tiny frog’s mating season. Today, it was just a few “peeps” among anxious friends.
Any additional river flow that resulted from the rains of the previous week is scarcely noticeable among the Pothole Rocks. The water level remains low, the water column is fairly clear, and the water temperatures are in the 60s Fahrenheit.
It’s no real surprise then to see aquatic turtles climbing onto the boulders in the falls to enjoy a little warmth, if not from the sun, then from the stored heat in the rocks. As usual, they’re quick to slide into the depths soon after sensing someone approaching or moving nearby. Seldom found anywhere but on the river, these skilled divers are Common Map Turtles (Graptemys geographica), also known as Northern Map Turtles. Their paddle-like feet are well adapted to swimming in strong current. They are benthic feeders, feasting upon a wide variety of invertebrates found among the stone and substrate of the river bottom.
Adult Common Map Turtles hibernate communally on the river bottom in a location protected from ice scour and turbulent flow, often using boulders, logs, or other structures as shelter from strong current. The oxygenation of waters tumbling through Conewago Falls may be critical to the survival of the turtles overwintering downstream. Dissolved oxygen in the water is absorbed by the nearly inactive turtles as they remain submerged at their hideout through the winter. Though Common Map Turtles, particularly males, may occasionally move about in their hibernation location, they are not seen coming to the surface to breathe.
The Common Map Turtles in the Susquehanna River basin are a population disconnected from that found in the main range of the species in the Great Lakes and upper Mississippi basin. Another isolated population exists in the Delaware River.
Committee on the Status of Endangered Wildlife in Canada. 2002. Status Report of the Northern Map Turtle. Canadian Wildlife Service. Ottawa, Ontario.
A moderate breeze from the south placed a headwind into the face of migrants trying to wing their way to winter quarters. The urge to reach their destination overwhelmed any inclination a bird or insect may have had to stay put and try again another day.
Blue Jays were joined by increasing numbers of American Robins crossing the river in small groups to continue their migratory voyages. Killdeer (Charadrius vociferous) and a handful of sandpipers headed down the river route. Other migrants today included a Cooper’s Hawk (Accipiter cooperii), Eastern Bluebirds (Sialia sialis), and a few Common Mergansers (Mergus merganser), House Finches (Haemorhous mexicanus), and Common Grackles (Quiscalus quiscula).
The afternoon belonged to the insects. The warm wind blew scores of Monarchs toward the north as they persistently flapped on a southwest heading. Many may have actually lost ground today. Painted Lady (Vanessa cardui) and Cloudless Sulphur butterflies were observed battling their way south as well. All three of the common migrating dragonflies were seen: Common Green Darner (Anax junius), Wandering Glider (Pantala flavescens), and Black Saddlebags (Tramea lacerata).
The warm weather and summer breeze are expected to continue as the rain and wind from Hurricane Nate, today striking coastal Alabama and Mississippi, progresses toward the Susquehanna River watershed during the coming forty-eight hours.
The Neotropical birds that raised their young in Canada and in the northern United States have now logged many miles on their journey to warmer climates for the coming winter. As their density decreases among the masses of migrating birds, a shift to species with a tolerance for the cooler winter weather of the temperate regions will be evident.
Though it is unusually warm for this late in September, the movement of diurnal migrants continues. This morning at Conewago Falls, five Broad-winged Hawks (Buteo platypterus) lifted from the forested hills to the east, then crossed the river to continue a excursion to the southwest which will eventually lead them and thousands of others that passed through Pennsylvania this week to wintering habitat in South America. Broad-winged Hawks often gather in large migrating groups which swarm in the rising air of thermal updrafts, then, after gaining substantial altitude, glide away to continue their trip. These ever-growing assemblages from all over eastern North America funnel into coastal Texas where they make a turn to south around the Gulf of Mexico, then continue on toward the tropics. In the coming weeks, a migration count at Corpus Christi in Texas could tally 100,000 or more Broad-winged Hawks in a single day as a large portion of the continental population passes by. You can track their movement and that of other diurnal raptors as recorded at sites located all over North America by visiting hawkcount.org on the internet. Check it out. You’ll be glad you did.
Nearly all of the other migrants seen today have a much shorter flight ahead of them. Red-bellied Woodpeckers (Melanerpes carolinus), Red-headed Woodpeckers (Melanerpes erythrocephalus), and Northern Flickers (Colaptes auratus) were on the move. Migrating American Robins (Turdus migratorius) crossed the river early in the day, possibly leftovers from an overnight flight of this primarily nocturnal migrant. The season’s first Great Black-backed Gulls (Larus marinus) arrived. American Goldfinches are easily detected by their calls as they pass overhead. Look carefully at the goldfinches visiting your feeder, the birds of summer are probably gone and are being replaced by migrants currently passing through.
By far, the most conspicuous migrant today was the Blue Jay. Hundreds were seen as they filtered out of the hardwood forests of the diabase ridge to cautiously cross the river and continue to the southwest. Groups of five to fifty birds would noisily congregate in trees along the river’s edge, then begin flying across the falls. Many wary jays abandoned their small crossing parties and turned back. Soon, they would try the trip again in a larger flock.
A look at this morning’s count reveals few Neotropical migrants. With the exception of the Broad-winged Hawks and warblers, the migratory species seen today will winter in a sub-tropical temperate climate, primarily in the southern United States, but often as far north as the lower Susquehanna River valley. The individual birds observed today will mostly continue to a winter home a bit further south. Those that will winter in the area of Conewago Falls will arrive in October and later.
The long-distance migrating insect so beloved among butterfly enthusiasts shows signs of improving numbers. Today, more than two dozen Monarchs were seen crossing the falls and slowly flapping and gliding their way to Mexico.
A few nocturnal migrants flew through the moonlit night to arrive at Conewago Falls for a sunrise showing this morning. A dozen warblers were in the treetops and a Wood Thrush (Hylocichla mustelina) chattered away in the understory of the Riparian Woodlands. Three species of shorebirds were in the falls and on the Pothole Rocks: Least Sandpiper (Calidris minutilla), Lesser Yellowlegs (Tringa flavipes), and Greater Yellowlegs (Tringa melanoleuca).
The diurnal migration was highlighted by a Merlin (Falco columbarius), an Osprey, and a Bald Eagle, each flying down the river. Most of the other birds in the falls seemed content to linger and feed. There’s no need to hurry folks, only trouble lurks down there in paradise at the moment.
A couple of inches of rain this week caused a small increase in the flow of the river, just a burp, nothing major. This higher water coincided with some breezy days that kicked up some chop on the open waters of the Susquehanna upstream of Conewago Falls. Apparently it was just enough turbulence to uproot some aquatic plants and send them floating into the falls.
Piled against and upon the upstream side of many of the Pothole Rocks were thousands of two to three feet-long flat ribbon-like opaque green leaves of Tapegrass, also called Wild Celery, but better known as American Eelgrass (Vallisneria americana). Some leaves were still attached to a short set of clustered roots. It appears that most of the plants broke free from creeping rootstock along the edge of one of this species’ spreading masses which happened to thrive during the second half of the summer. You’ll recall that persistent high water through much of the growing season kept aquatic plants beneath a blanket of muddy current. The American Eelgrass colonies from which these specimens originated must have grown vigorously during the favorable conditions in the month of August. A few plants bore the long thread-like pistillate flower stems with a fruit cluster still intact. During the recent few weeks, there have been mats of American Eelgrass visible, the tops of their leaves floating on the shallow river surface, near the east and west shorelines of the Susquehanna where it begins its pass through the Gettysburg Basin near the Pennsylvania Turnpike bridge at Highspire. This location is a probable source of the plants found in the falls today.
The cool breeze from the north was a perfect fit for today’s migration count. Nocturnal migrants settling down for the day in the Riparian Woodlands at sunrise included more than a dozen warblers and some Gray Catbirds (Dumetella carolinensis). Diurnal migration was underway shortly thereafter.
Four Bald Eagles were counted as migrants this morning. Based on plumage, two were first-year eagles (Juvenile) seen up high and flying the river downstream, one was a second-year bird (Basic I) with a jagged-looking wing molt, and a third was probably a fourth year (Basic III) eagle looking much like an adult with the exception of a black terminal band on the tail. These birds were the only ones which could safely be differentiated from the seven or more Bald Eagles of varying ages found within the past few weeks to be lingering at Conewago Falls. There were as many as a dozen eagles which appeared to be moving through the falls area that may have been migrating, but the four counted were the only ones readily separable from the locals.
Red-tailed Hawks (Buteo jamaicensis) were observed riding the wind to journey not on a course following the river, but flying across it and riding the updraft on the York Haven Diabase ridge from northeast to southwest.
Bank Swallows (Riparia riparia) seem to have moved on. None were discovered among the swarms of other species today.
Ruby-throated Hummingbirds, Caspian Terns, Cedar Waxwings (Bombycilla cedrorum), and Chimney Swifts (Chaetura pelagica) were migrating today, as were Monarch butterflies.
Not migrating, but always fun to have around, all four wise guys were here today. I’m referring to the four members of the Corvid family regularly found in the Mid-Atlantic states: Blue Jay (Cyanocitta cristata), American Crow (Corvus brachyrhynchos), Fish Crow (Corvus ossifragus), and Common Raven (Corvus corax).
Klots, Elsie B. 1966. The New Field Book of Freshwater Life. G. P. Putnam’s Sons. New York, NY.
Rain from the remnants of Hurricane/Tropical Storm Harvey ended just after daybreak this morning. Locally, the precipitation was mostly absorbed into the soil. There was little runoff and no flooding. The river level at Conewago Falls is presently as low as it has been all summer. Among the pools and rapids of the Pothole Rocks, numbers of migrating birds are building.
Mist and a low cloud ceiling created poor visibility while trying to see early morning birds, but they’re here. The warblers are moving south and a small wave of them was filtering through the foliage on the edge of the Riparian Woodlands. One must bend backwards to have a look, and most could not be identified due to the poor lighting in the crowns of the trees where they were zipping about. Five species of warblers and two species of vireos were discerned.
There are increasing concentrations of swallows feeding on insects over the falls. Hundreds were here today, mostly Tree Swallows (Tachycineta bicolor). Bank Swallows (Stelgidopteryx riparia) numbered in the hundreds, far below the thousands, often 10,000, which staged here for migration and peaked during the first week of September annually during the 1980s and 1990s. Their numbers have been falling steadily. Loss of nesting locations in embankments near water may be impacting the entire population. A reduction in the abundance of late-summer flying insects here on the lower Susquehanna River may be cause for them to abandon this area as a migration staging point.
Clear weather in the coming nights and days may get the migrants up and flying in large numbers. For those species headed to the tropics for winter, the time to get moving has arrived.
When we look at birds, we are fascinated by the unique structure and appearance of their feathers. They set birds apart from all other life forms on the planet. Feathers enable most birds to achieve a feat long envied by humans…flight. Birds on the wing awaken a curiosity in man. They are generally the largest animals one will see in the air. People want to know the name of a bird they see flying by, and want to know more about it. The method and style of bird flight can aid an observer who attempts to determine which of the world’s 10,000 bird species he or she is studying. Body shape and bird sounds often tell us a lot about the birds we encounter. But most often, we rely on the unique colors, patterns, and shapes of the feathers, the plumage, to identify the bird we are seeing.
To birds, feathers are survival. They are lightweight and strong to support the mechanics of flight. Feathers are superb insulators against the elements, and provide additional buoyancy for birds spending time on the water. For most birds, feathers provide a coloration and a texture similar to their surroundings, enabling them to hide from predators or to stalk prey. In the case of some species, extravagant showy plumage is acquired, at least during the breeding season, and often only by males, as a way to attract a mate, intimidate rivals, defend a territory, or lure an intruder away from a nest site. Because they become worn and damaged, all feathers are periodically molted and replaced by fresh plumage.
The feathers worn by a young bird leaving the nest are called the juvenile plumage. Typically, this is followed by a molt into a basic (non-breeding) plumage. The oft times extravagant breeding feathers are the result of a molt into an alternate (breeding) plumage.
While making field observations, the species, subspecies, gender, age, and other vital statistics of a bird can often by discerned easily by noting the plumage. In the case of some other birds, diligence, experience, research, and an exceptionally good look and/or a photograph may be required to interpret these particulars. In still other instances, a trained expert with a specimen in the hand is the only method of learning the bird’s identity and background.
The age at which birds acquire adult breeding and non-breeding plumages varies by species. Many juvenile birds resemble adults in basic (non-breeding) plumage as soon as they leave the nest. For these birds, there is little difference between their juvenile plumage and the appearance of the feathers which follow the molt into their first basic (non-breeding) plumage. Bird species which sexually mature within their first year may acquire their first basic (non-breeding) plumage before arrival of their first winter, followed by an alternate (breeding) plumage by their first spring. This is particularly true for smaller short-lived birds. Other species, normally larger long-lived ones, may experience a sequence of molts through multiple basic (non-breeding) plumages over a period of years prior to resembling an adult. Some of these species, such as eagles, retain their juvenile plumage for as long as a year before extensive molting into a first basic (non-breeding) plumage begins. Still others, including many gulls, attain a first-winter (formative) plumage prior to molting into their first basic (non-breeding) set of feathers. Sexual maturity and initiation of an annual molt to alternate (breeding) plumage, if there is one, may take as long as three to five years for these bigger birds.
For nearly all species of birds, the molts which produce basic (non-breeding) plumage occur on at least an annual basis and include a total replacement of feathers. This process renews worn and missing plumes including the flight feathers of the wings and tail. Any molt to alternate (breeding) plumage often excludes the replacement of the feathers of the wings and tail. There are many exceptions to these generalities.
The Juvenile and non-breeding (basic) plumages of late-summer may seem drab and confusing, but learning them is a worthwhile endeavor. Consider that most of the birds coming south during the migration will be adorned in this fashion. The birds of North America are in their greatest numerical mass of the year right now, and nearly all are females, juveniles, other non-adults, or molting males. There are few males in breeding plumage among the autumn waves of migrants. In the coming months, there will be an abundance of opportunities to enjoy these marvels on wings, so getting to know the birds in non-breeding feathers is time well spent. Make haste and get ready. For our feathered friends, it’s autumn and they’re on their way south.
Dunne, Pete. 2006. Pete Dunne’s Essential Field Guide Companion. Houghton Mifflin Company. New York.
Hayman, Peter; John Marchant, and Tony Prater. 1986. Shorebirds, An Identification Guide to the Waders of the World. Houghton Mifflin Company. New York.
Kauman, Kenn. 1996. Lives of North American Birds. Houghton Mifflin Company. New York.
McCullough, Mark A. 1989. Molting Sequence and Aging Of Bald Eagles. The Wilson Bulletin. 101:1-10.