It may seem hard to believe, but the autumn migration of shorebirds and many Neotropical songbirds is now well underway. To see the former in what we hope will be large numbers in good light, we timed a visit to the man-made freshwater impoundments at Bombay Hook National Wildlife Refuge near Smyrna, Delaware, to coincide with a high-tide during the mid-morning hours. Come along for a closer look…
Along a large portion of its route, the tour road at Bombay Hook N.W.R. sits atop the man-made dikes that create several sizeable freshwater pools (left) along the inland border of one of the largest remaining salt marsh estuaries in the Mid-Atlantic States (right).Twice daily, the rising tide from Delaware Bay flows along the tidal creeks to flood Bombay Hook’s extensive marshes.At high tide, mudflats in Bombay Hook’s coastal estuary become inundated by salt water, forcing migratory shorebirds to relocate to bay side beaches or other higher ground to rest and feed for several hours.At Bombay Hook, migratory shorebirds, waterfowl, and waders can find refuge from high tide in the freshwater impoundments created by capturing water along the inland west side of a system of earthen dikes.Mechanical or stacked-board gate systems are used to control water depth in the impoundments. Levels can be adjusted seasonally to manage plant growth and create conditions favorable for use by specific groups of birds and other wildlife.A map at Shearness Pool, the largest impoundment on the refuge, shows the location of other freshwater pools at Bombay Hook.A mix of mudflats and shallow water on Raymond Pool provides ideal habitat for a variety of shorebirds forced from the vast tidal marshes by the rising tide. For us, a mid-morning high tide places these birds in perfect light as they feed and loaf in the pools to the west of the tour road located atop the dikes.Migrating shorebirds arrive on Raymond Pool to find refuge from the rising tide to the east. Showing a single ring around their breast, many Semipalmated Plovers can be seen here among the Semipalmated Sandpipers, the latter the most abundant shorebird presently populating Bombay Hook. Feeding in deeper water in the background are Short-billed Dowitchers. All of these birds consume a variety of invertebrates they find both in and on the mud.Semipalmated Plovers and Semipalmated Sandpipers arriving on a mudflat at Raymond Pool.A Short-billed Dowitcher glides in from the salt marsh to visit the shallows of Raymond Pool for a couple of hours.A Short-billed Dowitcher feeding among Semipalmated Plovers and Semipalmated Sandpipers.Short-billed Dowitchers in water almost too deep for the Semipalmated Sandpipers in their company.A lone Black-bellied Plover (Pluvialis squatarola) among the abundance of Short-billed Dowitchers.Short-billed Dowitchers probe the mud with their sewing machine-like feeding style.Seldom do they take a break long enough for an observer to their bill in its entirety.A Lesser Yellowlegs arrives at Raymond Pool as a high-tide refugee.Another Lesser Yellowlegs on a mudflat.A Greater Yellowlegs wades into shallow water to feed.It’s difficult to estimate just how many Semipalmated Plovers and Semipalmated Sandpipers were seen. There were at least 500 plovers, and they were very vocal. The latter species was present in numbers measurable in the thousands. We don’t think 10,000 Semipalmated Sandpipers is an overestimate.Searching through the Semipalmated Sandpipers, one could regularly find a very similar species among them.We identified the longer-billed and slightly larger Western Sandpiper (Calidris mauri) and found the species to be present possibly by the hundreds among the masses of thousands of Semipalmated Sandpipers. These seem to be unusually high numbers for this more western species, but who’s complaining?As we sifted through these groups of tiny shorebirds known as “peeps”, we found Western Sandpipers (top) regularly distributed among the multitudes of Semipalmated Sandpipers (bottom) we encountered.A Western Sandpiper (top) photographed with a Semipalmated Sandpiper (bottom) in Bear Swamp Pool.Of course, shorebirds aren’t all there is to see at Bombay Hook. More than 100 Snowy Egrets were found on the freshwater pools alongside birds like this Semipalmated Plover.Great Egrets could be seen stalking small fish in the channels of the pools.And a few Green Herons were found lurking in the vegetation.This Osprey briefly startled the shorebirds on Raymond Pool until they realized it posed no threat.By early afternoon, we noticed the tide beginning to retreat from the saltwater marsh and mudflats opposite Shearness Pool. As shorebirds began returning there to feed, we decided to make our way to Raymond Pool to watch the exodus.With the high tide receding from the coastal estuary back into Delaware Bay, shorebirds promptly departed their concentrated environs on Raymond Pool to spread out over thousands of acres of salt marsh to feed.More shorebirds exit Raymond Pool en route to the adjacent tidal areas to feed. This outbound group includes two Black-bellied Plovers (top center and four birds to the right).These migrants have just begun their autumn journey from breeding grounds in Canada and Alaska to wintering areas located as far south as southern South America. For them, Bombay Hook and other refuges are irreplaceable feeding and resting locations to help them refuel for their long journey ahead. For them, a little vacation along the coast is a matter of life and death.A goodwill ambassador bids us farewell at the end of our visit to Bombay Hook. Remember to support your National Wildlife Refuges by purchasing your annual Federal Duck Stamp. They’re available right now at your local United States Post Office, at the Bombay Hook visitor’s center, or online at the United States Fish and Wildlife Service website.
Planning a visit? Here are some upcoming dates with morning high tides to coax the birds out of the tidal estuary and into good light in the freshwater impoundments on the west side of the tour road…
Tuesday, August 19 at approximately 07:00 AM EDT
Wednesday, August 20 at approximately 08:00 AM EDT
For migrating birds, the spring season is drawing to a close. The last of the Neotropical songbirds are now trickling through while the final waves of sandpipers and other shorebirds may have already cleared our region to continue their long journey north to breeding grounds in Canada and Alaska. From earlier this week…
A northbound Semipalmated Plover during a stopover in the Lower Susquehanna River Watershed. These smaller cousins of our local double-banded Killdeer are a tundra nesting species.A Semipalmated Plover and a small flock of Least Sandpipers feed and recharge on a mudflat.A Semipalmated Sandpiper (left) and a Least Sandpiper during a migration break. The latter species is on its way to taiga wetlands in Canada and Alaska to breed. Like the Semipalmated Plover, the Semipalmated Sandpiper continues beyond the taiga regions to nest in the tundra of the far north.This Greater Yellowlegs needs to hustle if it’s going to reach the species’ nesting grounds in the taiga of Canada in time to participate in this year’s breeding cycle. Otherwise, it may be among the early birds we see coming back south through our area as soon as late June, during the start of the fall migration.
You read it right. “Fall migration” often gets going by the first day of summer—southbound birds, less than a month away!
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).
Shorebird identification can be notoriously difficult, but it’s a skill best learned with practice. Now is a good time to become familiar with the two most common species of plovers found in the lower Susquehanna valley. Numbers of both are increasing on local mudflats as waves of southbound migrants begin to arrive. The Killdeer in the lower left is a familiar nesting species of barren fields, stone parking lots, and gravel roofs. Its numbers swell during spring and fall migration, with some lingering into winter until either snow cover or a hard freeze prompts them to finally depart for milder climes. The Semipalmated Plovers in the upper right are strictly a migratory species in our area, nesting in northern Canada and Alaska and wintering along the American coastlines from Oregon and Delmarva south to Chile and Argentina. You’ll notice that the Semipalmated Plover has just a single neck ring while the Killdeer has two. That’s how you can tell them apart in a jiffy. It’s that easy.
The southbound bird migration of 2020 is well underway. With passage of a cold front coming within the next 48 hours, the days ahead should provide an abundance of viewing opportunities.
Here are some of the species moving through the lower Susquehanna valley right now.
Blue-winged Teal are among the earliest of the waterfowl to begin southward migration.Sandpipers and plovers have been on the move since July. The bird in the foreground with these Killdeer is not one of their offspring, but rather a Semipalmated Plover (Charadrius semipalmatus), a regular late-summer migrant in the Lower Susquehanna River Watershed.Hawk watch sites all over North America are counting birds right now. The Osprey is an early-season delight as it glides past the lookouts. Look for them moving down the Susquehanna as well.Bald Eagles will be on the move through December. To see these huge raptors in numbers, visit a hawk watch on a day following passage of a cold front when northwest winds are gusting.Merlins were seen during this past week in areas with good concentrations of dragonflies. This particular one at Middle Creek Wildlife Management Area in Lancaster and Lebanon Counties……was soon visited by another.Check the forest canopy for Yellow-billed Cuckoos. Some local birds are still on breeding territories while others from farther north are beginning to move through.Ruby-throated Hummingbirds are darting through the lower Susquehanna valley on their way to the tropics. This one has no trouble keeping pace with a passing Tree Swallow.Nocturnal flights can bring new songbirds to good habitat each morning. It’s the best time of year to see numbers of Empidonax flycatchers. But, because they’re often silent during fall migration, it’s not the best time of year to easily identify them. This one lacking a prominent eye ring is a Willow Flycatcher (Empidonax traillii).During the past two weeks, Red-eyed Vireos have been numerous in many Susquehanna valley woodlands. Many are migrants while others are breeding pairs tending late-season broods.During mornings that follow heavy overnight flights, Blackburnian Warblers have been common among waves of feeding songbirds.Chestnut-sided Warblers are regular among flocks of nocturnal migrants seen foraging among foliage at sunrise.Scarlet Tanagers, minus the brilliant red breeding plumage of the males, are on their way back to the tropics for winter.While passing overhead on their way south, Bobolinks can be seen or heard from almost anywhere in the lower Susquehanna valley. Their movements peak in late August and early September.During recent evenings, Bobolinks have been gathering by the hundreds in fields of warm-season grasses at Middle Creek Wildlife Management Area.If you go to see the Bobolinks there, visit Stop 3 on the tour route late in the afternoon and listen for their call. You’ll soon notice their wings glistening in the light of the setting sun as they take short flights from point to point while they feed. Note the abundance of flying insects above the Big Bluestem and Indiangrass in this image. Grasslands like these are essential habitats for many of our least common resident and migratory birds.
