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…
One of a hundred or more Least Sandpipers seen on mudflats at Lake Redman today.A Semipalmated Plover and a Least SandpiperPectoral Sandpipers.A Pectoral Sandpiper and two Least Sandpipers.A Semipalmated Sandpiper.A Stilt Sandpiper feeding.Stilt Sandpiper consuming an edible.Stilt Sandpiper at rest.A Solitary SandpiperA Lesser Yellowlegs.A Greater Yellowlegs.Stirring up the shorebird crowd every now and then were several Ospreys, but all would soon be back to the business of feeding in the mud.An Osprey hovers above shallow water near the mudflats as it searches for fish.
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.
Designed to prevent stream flooding and pollution, this recently installed stormwater retention basin along US 322 west of Hershey, Pennsylvania, has already attracted a variety of migrating plovers and sandpipers.Killdeer stick close to exposed mud as they feed.Two of more than a dozen Least Sandpipers found busily feeding in the inch-deep water.A Lesser Yellowlegs searching for small invertebrates.Two Lesser Yellowlegs work out a disagreement.Male Twelve-spotted Skimmers patrol the airspace above a pair of Least Sandpipers. Dragonflies and other aquatic insects are quick to colonize the waters held in well-engineered retention basins. Proper construction and establishment of a functioning food chain/web in these man-made wetlands prevents them from becoming merely temporary cesspools for breeding mosquitos.
So don’t just drive by those big puddles, stop and have a look. You never know what you might find.
A Semipalmated Sandpiper (middle right) joins a flock of Least Sandpipers.Pectoral Sandpipers (two birds in the center) are regular fall migrants on the Susquehanna at this time of year. They are most frequently seen on gravel and sand bars adjacent to the river’s grassy islands, but unusually high water for this time of year prevents them from using this favored habitat. As a result, you might be lucky enough to discover Pectoral Sandpipers on almost any mudflat in the area.Two Pectoral Sandpipers and five smaller, but otherwise very similar, Least Sandpipers.A Killdeer (right), a Semipalmated Plover (upper right), and Least and Pectoral Sandpipers (left).
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.
Your Federal Duck Stamp is your admission ticket for entry into many of the country’s National Wildlife Refuges including Bombay Hook National Wildlife Refuge on Delaware Bay near Smyrna, Delaware.
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.
This pair of Northern Bobwhite, a species now extirpated from the Lower Susquehanna River Watershed and the rest of Pennsylvania, escorted us into the refuge. At Bombay Hook, they don’t waste your money mowing grass. Instead, a mosaic of warm-season grasses and early successional growth creates ideal habitat for Northern Bobwhite and other wildlife.Twice each day, high tide inundates mudflats in the saltwater tidal marshes at Bombay Hook prompting shorebirds to move into the four man-made freshwater pools. Birds there can often be observed at close range. The auto tour route through the refuge primarily follows a path atop the dikes that create these freshwater pools. Morning light is best when viewing birds on the freshwater side of the road, late-afternoon light is best for observing birds on the tidal saltwater side.A Great Blue Heron at high tide on the edge of a tidal creek that borders Bombay Hook’s tour route at Raymond Pool.Semipalmated Sandpipers stream into Raymond Pool to escape the rising tide in the salt marsh.More Semipalmated Sandpipers and a single Short-billed Dowitcher (Limnodromus griseus) arrive at Raymond Pool.Two more Short-billed Dowitchers on the way in.Recent rains have flooded some of the mudflats in Bombay Hook’s freshwater pools. During our visit, birds were often clustered in areas where bare ground was exposed or where water was shallow enough to feed. Here, Short-billed Dowitchers in the foreground wade in deeper water to probe the bottom while Semipalmated Sandpipers arrive to feed along the pool’s edge. Mallards, American Avocets, and egrets are gathered on the shore.More Short-billed Dowitchers arriving to feed in Raymond Pool.Hundreds of Semipalmated Sandpipers gathered in shallow water where mudflats are usually exposed during mid-summer in Raymond Pool.Hundreds of Semipalmated Sandpipers, several Short-billed Dowitchers, and some Forster’s Terns (Sterna forsteri) crowd onto a mud bar at Bear Swamp Pool.A zoomed-in view of the previous image showing a tightly packed crowd of Semipalmated Sandpipers, Forster’s Terns, and a Short-billed Dowitcher (upper left).Short-billed Dowitchers wading to feed in the unusually high waters of Raymond Pool.Short-billed Dowitchers, American Avocets, and a Snowy Egret in Raymond Pool. A single Stilt Sandpiper (Calidris himantopus) can been seen flying near the top of the flock of dowitchers just below the egret.Zoomed-in view of a Stilt Sandpiper (Calidris himantopus), the bird with white wing linings.American Avocets probe the muddy bottom of Raymond Pool.Among these Short-billed Dowitchers, the second bird from the bottom is a Dunlin. This sandpiper, still in breeding plumage, is a little bit early. Many migrating Dunlin linger at Bombay Hook into October and even November.This Least Sandpiper found a nice little feeding area all to itself at Bear Swamp Pool.Lesser Yellowlegs at Bear Swamp Pool.Lesser Yellowlegs at Bear Swamp PoolA Greater Yellowlegs at Bear Swamp Pool.A Caspian Tern patrolling Raymond Pool.The chattering notes of the Marsh Wren’s (Cistothorus palustris) song can be heard along the tour road wherever it borders tidal waters.This dome-shaped Marsh Wren nest is supported by the stems of Saltwater Cordgrass (Sporobolus alterniflorus), a plant also known as Smooth Cordgrass. High tide licks at the roots of the cordgrass supporting the temporary domicile.By far the most common dragonfly at Bombay Hook is the Seaside Dragonlet (Erythrodiplax berenice). It is our only dragonfly able to breed in saltwater. Seaside Dragonlets are in constant view along the impoundment dikes in the refuge.Red-winged Blackbirds are still nesting at Bombay Hook, probably tending a second brood.Look up! A migrating Bobolink passes over the dike at Shearness Pool.Non-native Mute Swans and resident-type Canada Geese in the rain-swollen Shearness Pool.A pair of Trumpeter Swans (Cygnus buccinator) as seen from the observation tower at Shearness Pool. Unlike gregarious Tundra and Mute Swans, pairs of Trumpeter Swans prefer to nest alone, one pair to a pond, lake, or sluggish stretch of river. The range of these enormous birds was restricted to western North America and their numbers were believed to be as low as 70 birds during the early twentieth century. An isolated population consisting of several thousand birds was discovered in a remote area of Alaska during the 1930s allowing conservation practices to protect and restore their numbers. Trumpeter Swans are slowly repopulating scattered east coast locations following recent re-introduction into suitable habitats in the Great Lakes region.A Great Egret prowling Shearness Pool.A Snowy Egret in Bear Swamp Pool.Wood Ducks in Bear Swamp Pool.A Bombay Hook N.W.R. specialty, a Black-necked Stilt and young at Bear Swamp Pool.
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.
Bombay Hook National Wildlife Refuge protects a vast parcel of tidal salt marsh and an extensive network of tidal creeks. These areas are not only essential wildlife habitat, but are critical components for maintaining water quality in Delaware Bay and the Atlantic.The shells of expired Atlantic Horseshoe Crabs were formerly widespread and common among the naturally occurring flotsam along the high tide line on Delaware Bay. We found just this one during our visit to Bombay Hook. Man has certainly decimated populations of this ancient crustacean during recent decades.As the tide goes out, it’s a good time for a quick walk into the salt marsh on the boardwalk trail opposite Raymond Pool.Among the Saltmarsh Cordgrass along the trail and on the banks of the tidal creek there, a visitor will find thousands and thousands of Atlantic Marsh Fiddler Crabs (Minuca pugnax).Atlantic Marsh Fiddler Crabs and their extensive system of burrows help prevent the compaction of tidal soils and thus help maintain ideal conditions for the pure stands of Saltwater Cordgrass that trap sediments and sequester nutrients in coastal wetlands.A male Atlantic Marsh Fiddler Crab peers from its den.Herons and egrets including this Great Egret are quite fond of fiddler crabs. As the tide goes out, many will venture away from the freshwater pools into the salt marshes to find them.A Green Heron seen just before descending into the cordgrass to find fiddler crabs for dinner.A juvenile Clapper Rail (Rallus crepitans crepitans) emerges from the cover of the cordgrass along a tidal creek to search for a meal.Glossy Ibis leave their high-tide hiding place in Shearness Pool to head out into the tidal marshes for the afternoon.Great Black-backed Gulls, Herring Gulls, and possibly other species feed on the mudflats exposed by low tide in the marshes opposite Shearness Pool.An Osprey patrols the vast tidal areas opposite Shearness Pool.
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.
Indigo Buntings nest in areas of successional growth and yes, that is a Spotted Lanternfly on the grape vine at the far right side of the image.Blue Grosbeaks (Passerina caerulea) are common nesting birds at Bombay Hook. This one was in shrubby growth along the dike at the north end of Shearness Pool.These two native vines are widespread at Bombay Hook and are an excellent source of food for birds. The orange flowers of the Trumpet Vine are a hummingbird favorite and the Poison Ivy provides berries for numerous species of wintering birds.The Pileated Woodpecker is one of the numerous birds that supplements its diet with Poison Ivy berries. The tree this individual is visiting is an American Sweetgum (Liquidambar styraciflua), a species native to the Atlantic Coastal Plain in Delaware. The seed balls are a favorite winter food of goldfinches and siskins.Finis Pool has no frontage on the tidal marsh but is still worth a visit. It lies along a spur road on the tour route and is located within a deciduous coastal plain forest. Check the waters there for basking turtles like this giant Northern Red-bellied Cooter (Pseudemys rubiventris) and much smaller Painted Turtle.The White-tailed Deity is common along the road to Finis Pool.Fowler’s Toads (Anaxyrus fowleri) breed in the vernal ponds found in the vicinity of Finis Pool and elsewhere throughout the refuge.The National Wildlife Refuge System not only protects animal species, it sustains rare and unusual plants as well. This beauty is a Turk’s Cap Lily (Lilium superbum), a native wildflower of wet woods and swamps.Just as quail led us into the refuge this morning, this Wild Turkey did us the courtesy of leading us to the way out in the afternoon.
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.
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.
Bank and Tree Swallows by the hundreds were feeding upon flying insects above the waters of Conewago Falls today. Lesser numbers of Northern Rough-winged Swallows (Stelgidopteryx serripennis) and Barn Swallows (Hirundo rustica) joined the swarm.
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.
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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.
This juvenile House Wren (Troglodytes aedon) left the nest wearing plumage very similar to that of its parents. In lieu of bright colors, the male House Wren relies upon a vigorous bubbly song and a scrappy demeanor to defend its breeding territory. This species nests in cavities on the edges of the Riparian Woodlands of Conewago Falls. Males may have more than one mate. House Wrens probably migrate at night and will winter in the southern border states and further south.
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.
A mid-summer nesting species, the American Goldfinch, Spinus tristis, male (left and right) molts into a glamorous alternate plumage for the breeding season. The adult female’s alternate plumage (top) is a subdued green-yellow and black. Her feathers resemble the foliage around the nest and offer protection from discovery during incubation. Juvenile plumage (bottom) is similar to that of the female, but duller with a buffy tone. By November each of these birds will have molted into a tan-buff basic (non-breeding) plumage, the male’s with a slight yellow hue. During their first spring, juveniles attain sexual maturity and, like the adults from the previous year, molt into alternate (breeding) plumage. The breeding birds seen here will probably winter in the southern United States, and birds that nested to our north will arrive to remain as winter residents. Various stages of molt can be seen simultaneously during spring and autumn migrations as populations of goldfinches from multiple latitudes intermingle as they pass through the Susquehanna River watershed.This juvenile Spotted Sandpiper (Actitis macularius), lacks the namesake dark markings on its white underside, thus it presently resembles an adult in basic (non-breeding) plumage. Upon reaching sexual maturity, it will molt into a spotted alternate (breeding) plumage for the nesting season during each remaining year of its life. Females of this species defend a territory and lay eggs in a nest located among cover near the shoreline. A female may have as many as five mates. Males alone incubate the eggs, usually four, for 20-24 days. The young leave the nest upon hatching and are escorted by the male for about two to three additional weeks. They are the only sandpiper to nest on the Susquehanna River shoreline. Spotted Sandpipers migrate to the southern border states and further south for winter. At Conewago Falls, they arrive in late April to nest, with birds, possibly migrants from further north, remaining until well into October. In any plumage, you can easily recognize the Spotted Sandpiper by its habit of teetering its body at the hips to pump the tail up and down.Bald Eagles go through a series of five molts before reaching adult plumage. The first plumage, Juvenile, is nearly all dark brown with white linings along the forward underside of the wings. The wing and tail feathers are a bit longer than in later plumages to aid the inexperienced birds during their clumsy first flights. Due to the additional feather length, Juveniles look larger than older birds, but they are not as heavy as their seniors. The bird seen here flying above Conewago Falls is probably in its second year. This plumage, Basic I, also known as “White Belly I”, is characterized by a nearly full set of new flight feathers. Note that some of the longer Juvenile feathers are still present, giving the wings a jagged sloppy look, particularly near the center of the trailing edge. Third-year (Basic II) birds often have at least some white belly feathers and are sometimes known as “White Belly II” Bald Eagles. Basic II birds typically possess a complete set of adult flight feathers, so the trailing edge of the wing has a neater and more uniform appearance.
The Bald Eagle in the two photographs above is in its first year. This plumage, known as “Juvenile”, is characterized by dark flight feathers which appear uniformly long in length when the bird is airborne. The eye is dark brown. The iris of the eye will lighten in the second year (Basic I) and will become cream-colored by the third year (Basic II). The bill, which is all dark gray when the bird is in the nest, has begun the slow progression to a yellow color that will be complete in the bird’s fifth year (Basic IV). Third year (Basic II) birds molt to white crown and throat feathers, but have a dark set of feathers through the eye producing an “Osprey face” in most individuals. In its fourth year (Basic III), this eagle will molt to a white tail with just a thin dark brown terminal band. The head will become nearly all white except for a few dark spots through the eye, which will have a yellow iris. A cleaner white head and tail will develop during the fifth year (Basic IV) and will persist through the familiar adult Bald Eagle plumages (Definitive Plumage) for the remainder of its life.
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.
Here come the confusing fall migrants. Twelve Semipalmated Sandpipers (Calidris pusilla) and sixteen unidentified “peep” sandpipers (Calidris species) were seen feeding in Conewago Falls on August 27. This Semipalmated Sandpiper is either an adult in worn alternate (breeding) plumage or a Juvenile. Adults of this species molt into basic plumage on the wintering grounds. The Semipalmated Sandpiper breeds in the high arctic tundra and winters in the West Indies and northern South America.CLICK ON THE LOGO FOR TODAY’S MIGRATION COUNT TOTALS
SOURCES
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.
