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
