Delaware Bay
Description: Delaware Bay is a major spring migration site for shorebirds on the Atlantic
flyway. The bay shorelines in New Jersey and Delaware provide feeding, resting and
roosting habitat for shorebirds during migration. In Delaware, this shoreline is made up
of narrow sandy beaches and low tide flats including dunes, sandy/muddy mouths of
rivers, adjacent tidal salt marshes and saltwater impoundments. The area comprises
approximately fifty miles of shoreline, stretching from Woodland Beach to Cape
Henlopen. In addition, there are extensive freshwater and saltwater wetlands throughout
the Delaware River and Bay estuary.
Ownership along the bay shoreline is a mix of private, state and federal land. The bay
shoreline is not heavily developed and many towns along the bay are fishing villages
inhabited more heavily in the summer. On the Delaware side of the Bay, about 50% of
the coastline, 20,670 hectares (51,054 acres) of wetlands are in state or federal ownership
and thus protected. Delaware Wildlife Management Areas include: Woodland Beach,
Little Creek, Ted Harvey, Milford Neck and Cape Henlopen. Federal areas under
protection include Bombay Hook and Prime Hook National Wildlife Refuges, managed
by the U.S. Fish and Wildlife Service.
Delaware is a very important state for migrating shorebirds. The spring migration of
shorebirds coincides with horseshoe crab spawning in Delaware Bay. Shorebirds have
been found to feed mostly on horseshoe crab eggs on the bay beaches, but surveys by NJ
Department of Fish and Wildlife indicate some species, such as the Semipalmated
Sandpiper, Dunlin and Short-billed Dowitcher, rely heavily on marsh habitats. Shorebirds
move between the beaches and marshes for feeding, resting and roosting. The most
abundant shorebird species in Delaware Bay during migration are: Semipalmated
Sandpipers, Ruddy Turnstones, Red Knots, Sanderlings, Dunlin and Short-billed
Dowitchers.
The movement patterns on Delaware Bay beaches are known to be very complex, with
much movement between sites and even between states at least during spring. According
to Bruce Peterjohn, there have been color-banded birds observed in DE, then in NJ a few
days later and then back in DE before they departed for points north.
Shorebird use of Delaware Bay beaches is also fairly significant during fall migration,
especially through late August and into early September, when the adults are moving
south. Use diminishes greatly after Labor Day, but small numbers occur throughout
autumn. Fall surveys along the Delaware Bay beaches are definitely necessary. Unless
aerial surveys are conducted in fall, as occurs during spring, fall ground surveys should
include all of the important beaches for roosting and foraging shorebirds.
The highest concentration of shorebirds on the bay shoreline occurs from the southern tip
of Bombay Hook at Port Mahon to the southern edge of Slaughter Beach. There are seven
major survey areas within this area: Port Mahon, Little Creek SWA, Pickering Beach,
Ted Harvey SWA, Bowers Beach to South Bowers, Brockonbridge Gut and the
Mispillion River Mouth to Slaughter Beach. Another shorebird hotspot in this area is
Kitts Hummock.
Maximum count data from ISS records were available for the following sites in Delaware
Bay:
Kitts Hummock/Ted Harvey WMA: BBPL (104), SEPL (1,476), DUNL (3,000), GRYE
(130), LESA (2,650), SESA (10,600), REKN (5,147), RUTU (3,000) and SBDO (3,360).
Little Creek WMA Beach: LESA (320), SESA (2,508), REKN (900), RUTU (2,200) and
SBDO (68).
Little Creek WMA Impoundment: DUNL (216), GRYE (449), LEYE (544), LESA (100),
SESA (300) and SBDO (500).
The Delaware Department of Fish and Wildlife Nongame and Endangered Species
Program, in conjunction with the NJ Division of Fish and Wildlife (NJ DFW), conducts
annual ground and aerial surveys of shorebird abundance on beaches. The Delaware work
involves ground counts of shorebirds and cannon netting for color banding and research.
The aerial surveys are conducted by NJ DFW biologist, Kathleen Clark. These surveys
occur once a week from the beginning of May to mid-June and cover the bay shoreline of
New Jersey (Cohansey River to Cape May Canal) and Delaware (Woodland Beach to
Cape Henlopen).
Survey Method: Ground, boat and aerial surveys are needed to cover extensive areas.
The NJ DFW aerial surveys covering Woodland Beach to Cape Henlopen are done on
early falling tides when crab eggs are exposed for feeding. During autumn migration,
ground surveys should be conducted of all important bayshore beaches.
Selection Bias: Spring survey work covers the bay beaches, but not the marshes. The bay
marshes are inaccessible except by air or boat and boat surveys only cover the marsh
edges.
Measurement Error/Bias: During the spring aerial surveys, some ground surveys
should be conducted at the same time to establish measurement error and bias from the
air. One cannot assume that the aerial surveys are detecting every individual, and
detection rates are likely to be species specific. Hence, the need for coordinated spring
ground surveys for developing aerial detection rates and more robust estimates of
population size.
Pilot Studies: Karen Bennett, Delaware Division of Fish & Wildlife, coordinated Fall
2003 surveys of the Delaware bayshore, Atlantic coast and impoundments. The surveys
were done to help determine what areas shorebirds use during fall migration and to
determine juvenile to adult ratios for selected species. The survey work was done in
conjunction with New Jersey Division of Fish and Wildlife, involving aerial surveys of
the entire bay and Atlantic coasts of both states.
Local Contacts: Karen Bennett, Natural Heritage and Endangered Species, DNREC
David Carter, Delaware Coastal Programs, DNREC
Bruce Peterjohn, USGS Patuxent Wildlife Research Center
Site 1: Port Mahon Beach
Description: Port Mahon beach comprises a 1 to 1 ½ mile stretch of beach below the
mouth of the Mahon River in Delaware Bay. A pipeline runs along the county road here
and provides the main jet fuel supply for Dover Air Force Base to the southwest. There is
a public boat launch at the end of the road and this spot is popular with bank fishermen
and crabbers. In the past, the road was lined with fishing shacks, docks, oyster shucking
houses and some residences, but these have long since eroded into the bay. The site
attracts large numbers of migrant shorebirds that feed and concentrate along the entire
length of the beach.
Access to Port Mahon is by Route 89 (Port Mahon Road) east out of the town of Little
Creek. The dirt portion of this road is very narrow in places and subject to seasonal
flooding. Note: using the road during or after a hard or long rain is not recommended
since it may become impassible. The entire area should be considered Type1 habitat.
Survey Method: Driving Port Mahon Road or walking the length of the beach. The tidal
flats are extensive at low tide and birds are too widely dispersed to survey adequately.
Surveys should be conducted during the first hour of falling tide, when birds are active
but still concentrated in easily viewed locations near the road.
Fishermen use this site heavily on weekends, which disturbs shorebirds and may cause
them to move. Therefore, surveys should be conducted on weekdays whenever possible.
Selection Bias: Not applicable, all areas should be accessible.
Measurement bias: Public use of this site is a significant factor that can lead to a
resulting bias. Such use should be documented during surveys so that changes in
shorebird disturbance are not confounded with changes in shorebird populations.
Measurement Error: Obtaining accurate counts of birds actively feeding at this site can
be difficult, especially when large numbers of multiple species are present.
Pilot Studies: A pilot study may be needed to determine how measurement error varies
among species at this site.
Site 2: Little Creek State Wildlife Area
Description: Little Creek State Wildlife Area consists of over 4,500 acres on the
Delaware coast and is broken up into two sections, the smaller of which adjoins Bombay
Hook NWR. Little Creek SWA is owned and managed by Delaware Division of Fish and
Wildlife. The shorebird survey areas are the impoundments near the town of Little Creek:
the northern one is known as Port Mahon impoundment and the southern one is called
Little Creek impoundment. Alternately, they are referred to as Little Creek north and
Little Creek south. There is also a small, center impoundment located in between. Large
numbers of shorebirds concentrate at this site in the fall.
Access: To access the north impoundment, take Port Mahon Road (county road 89) east
from the town of Little Creek. The impoundment is on the right. There is a small platform
in one corner that provides a vantage point for a portion of the impoundment. Views here
are limited to access points at the northeast and northwest corners and along a dike
bordering the western margin of the impoundment. Much of the dike is covered with
Phragmites and essentially impassible, with views into the impoundment through the tall
grass difficult to obtain.
The central and south impoundments may be accessed from headquarters of Little Creek
SWA, located just south of the town of Little Creek off Route 9. The entrance is well
marked; it looks private, but isn’t. After passing the buildings here, the road narrows and
enters a wooded area. Further on is a small parking lot and boardwalk that travels through
woods to an observation tower. Here you can park, walk out between impoundments or
take the boardwalk to the observation tower overlooking Little Creek south. The tower
gives views onto part of the impoundment, but the bulk of it is removed from this vantage
point. The dikes of Little Creek south are also covered with Phragmites, reducing access
in much of the surrounding area.
Most numerous species from International Shorebird Survey (ISS) records for the
following sites within Little Creek SWA are:
Little Creek, north impoundment: BBPL (100), SEPL (182), AMAV (180), GRYE
(1,000), LEYE (1,600), WILL (750), RUTU (400), REKN (100), SESA (3,800), LESA
(300), DUNL (5,000), SBDO (760), PEEP (8,000).
Little Creek, center impoundment: SEPL (45), AMAV (225), GRYE (454), LEYE (100),
SESA (800), LESA (60), SBDO (50), PEEP (200).
Little Creek, south impoundment: BBPL (129), SEPL (523), GRYE (870), LEYE (523),
REKN (150), SESA (6,500), DUNL (5,025), SBDO (2,000).
Survey Method: Ground surveys should be conducted within two hours of high tide.
These are large impoundments lacking good access, and may require surveyors to
negotiate dense Phragmites.
According to Kevin Kalasz, Delaware Division of Fish and Wildlife, shorebirds may be
viewed by walking along the levee which loops around Little Creek south, particularly
where it bends sharply on the northern edge and heads due east for the bay shore. Here
one can glass back into Little Creek south with a scope.
However, sun is a problem at both of these large impoundments. In the south
impoundment, lighting conditions are generally best in late afternoon/evening. For the
north impoundment, some vantage points will be in bad light regardless of when the
surveys are conducted. So survey timing for the north impoundment should depend upon
where birds are concentrated within it and the extent of cloud cover, as opposed to tidal
stage, which is not as important here.
Another confounding factor is the presence of a Peregrine Falcon nesting tower adjacent
to the south impoundment. Falcons regularly hunt both impoundments, raising havoc and
chasing birds out of the impoundments for long periods of time.
Selection Bias: Selection bias will be a factor as vegetation prevents one from seeing far
into the impoundments. Surveyors should attempt to see into all or as much of them as
possible with the aid of observation platforms and a scope, but even then this may prove
very difficult.
Furthermore, changes in vegetation within the pools could reduce the amount of suitable
habitat available to shorebirds. These changes need to be recorded to determine the extent
to which such bias is occurring.
Measurement Error: This may vary among species viewed at a distance within the large
impoundments for which generic identifications (i.e., “peeps”) may be the norm.
Measurement Bias: Any shift from specific to generic identifications (or vice versa)
could result in significant bias.
Pilot Studies: Pilot studies are needed to determine the extent of low detection rates due
to visibility problems at the large impoundments. Aerial surveys may be needed to
establish the accuracy of ground surveys.
Site 3: Pickering Beach
The description for this site is in the process of being refined and completed. We would
welcome any information by those with knowledge of the area.
Site 4: Ted Harvey State Wildlife Area
Description: Ted Harvey State Wildlife Area is located between Kitts Hummock and
Bowers Beach where the St. Jones River flows into Delaware Bay. It is owned and
managed by Delaware Division of Fish and Wildlife. Access is from the intersection of
US 113 and Del 9. Take county road 68 (Kitts Hummock Road). Turn south following
signs for Ted Harvey SWA, about 3 miles east of Dover Air Force Base or 2 miles west
of Kitts Hummock. There is a private house about 1/4 to 1/2 mile down the road. Just
before it, there is a side road to the left that leads to the bay. Near the end of the road,
there is a parking lot and small sign forbidding further passage by car. There is a gate and
the rule is enforced. Park here and walk along the levee to the beach (100 yards or so) to
an observation platform overlooking the bay and mud flats.
Shorebird survey areas include the bay shore, impoundments and the many shallow pools
located in the northerly section of Ted Harvey. These can be viewed by walking north
along the beach or the levee overlooking the shore. To reach the impoundments, return to
the house just before the parking area and turn left on the main road. Where the road
takes a sharp left (with a smaller road going straight) take the left fork to the
impoundment at the end of this road.
Survey Method: The mud flats along the bay shore at Ted Harvey are very extensive at
low tide and shorebirds are too far out to survey adequately. The best times for surveying
the bay shore is during the last hour of the rising tide or the first hour of the falling tide,
when shorebirds are on the beach and relatively close to observers.
The freshwater impoundments are large with relatively poor access and visibility; only
portions are visible from the ground. Additionally, vegetation within the impoundments
limits visibility of birds from the few vantage points. Shorebirds move from the bayshore
into the freshwater impoundments at Ted Harvey, so the surveys of the impoundments
should occur during a 2-hour period centered on high tide. Lighting conditions are not a
problem at the north impoundment, but can be a problem at the south impoundment,
where viewing from the north and east can be difficult during much of the day. Vantage
points from the south dike tend to be very distant from where the shorebirds congregate
and may not allow for accurate identification of most birds present in the impoundment.
Selection Bias: The north impoundment has only one accessible vantage point and birds
at the north side of the impoundment are difficult to view at all times. Vegetation also
obscures portions of this impoundment. The south impoundment has dense vegetation
growing along the margins, limiting visibility of the center where most shorebirds occur.
Both impoundments have areas that cannot be surveyed and could contribute to selection
bias, especially if there is a trend in the use of these areas over time.
Measurement Error: This may vary among species viewed distantly within the large
impoundments for which generic identifications (i.e., “peeps”) may be the norm.
Measurement Bias: Emergent vegetation continues to encroach onto the south
impoundment, reducing shorebird use of the area. Changes in vegetation need to be
recorded to determine the extent to which a resulting bias is occurring.
Pilot Studies: A pilot study is needed to establish how measurement error varies among
species viewed distantly at this site. Another is needed to calculate low detection rates at
inaccessible impoundment areas that receive high shorebird use. Periodic aerial surveys
may be needed to help adjust survey data taken from the ground.
Local contacts: Wayne Lehman, Regional Biologist, Ted Harvey SWA
(302) 653 - 2079
Site 5: Bowers Beach (North and South)
The description for this site is in the process of being refined and completed. We would
welcome any information by those with knowledge of the area.
Site 6: Brockonbridge Gut
The description for this site is in the process of being refined and completed. We would
welcome any information by those with knowledge of the area.
Site 7: Slaughter Beach/Mispillion River Mouth
The description for this site is in the process of being refined and completed. We would
welcome any information by those with knowledge of the area.