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The Importance of Migratory Stopovers

Delaware Bay, New Jersey

General Information

Stopover habitats are essential to successful bird migrations. Migrating birds need these critical stopover locations in the same way we need gas stations, restaurants, hotels and rest areas when we take long trips. Strategically located patches of woods, wetlands, mudflats, and beaches with adequate food and shelter ensure the survival of a species. As development continues to remove such habitats from our landscape, it becomes increasingly difficult for exhausted migrants to find suitable areas to rest and refuel.

 

Reed's Beach, and a few other stretches of beach along the southern shores of Delaware Bay, are one such migratory stopover. In the spring, millions of shorebirds leave their winter homes in South America and time their arrival on these beaches to coincide with the prehistoric mating ritual of the Horseshoe Crab. As seen in this photo, vast numbers of shorebirds compete for space and food where development has already occurred.

 

Reed’s Beach
Figure 1 - Reed’s Beach,
Delaware Bay, New Jersey

Horseshoe Crabs -
Figure 2 - Horseshoe Crabs -
Male and Female

In May, coinciding with the high tides that accompany the full moon, Horseshoe Crabs respond to a primitive urge to leave the depths of Delaware Bay and move to the shallows to mate and lay their eggs.

Bird banding studies show that each year, with impeccable timing, virtually the entire east coast population of Sanderlings, Semipalmated Sandpipers, Ruddy Turnstones, and Red Knots, leave their South American homes and arrive on these beaches on their journey to their breeding grounds in the far north. Estimates are that the survival of 4/5ths of the east coast population of Red Knots is dependent on the abundance of Horseshoe Crab eggs found on these few miles of beach.

 

Shown here among the sand grains and shell fragments are the small green eggs of the Horseshoe Crab. Billions of these eggs, laid in the sand, become the food for migrating shorebirds. Those eggs that survive this feathered banquet become the crabs for future generations.

 

Horseshoe Crab Eggs in Sand
Figure 3 - Horseshoe Crab Eggs in Sand

Gulls in a Feeding Frenzy
Figure 4 - Gulls in a Feeding Frenzy

The Laughing Gull has an unusual and comical feeding strategy. Instead of digging or probing for Horseshoe Crab eggs, they stand in one place and quickly stomp their feet up and down to force the Horseshoe Crab eggs from the sand. They then sip the eggs from the water.

 

Horseshoe Crabs stranded above the tide line can survive the exposure until the next high tide, but they often become prey to foraging birds such as this Greater Black-backed Gull.

Greater Black-backed Gull
Figure 5 - Greater Black-backed Gull

 

Underside of Horseshoe Crab
Figure 6 - Underside of Horseshoe Crab

 

Although the many sets of claws look formidable, the Horseshoe Crab is harmless, and quite helpless when stranded.

Many migrating birds that do find suitable beaches to feed and rest suffer harassment from beachwalkers, joggers, pet dogs, off-road vehicles, fishermen and even well meaning birdwatchers. These birds, on an already tight time and energy budget, must continually interrupt their feeding to flee, then return to resume their feeding.

 

 Shorebirds in Flight
Figure 7 - Shorebirds in Flight

 Efforts to Protect Critical Habitats
Figure 8 - Efforts to Protect Critical Habitats

 

The importance of Delaware Bay Beaches and other migratory stopovers are now recognized. Educational efforts to minimize disturbance to migrating birds have met with success, but much more needs to be done.

Volunteers from the Cape May Bird Observatory explain these critical ecological relationships to visitors.

Conservation Programs to Educate
Figure 9 - Conservation Programs to Educate

 

 Piping Plover
Figure 10 - Piping Plover

Some species, like this Piping Plover, are dependent on quiet beach habitats for breeding. Their preference for nesting on open beaches has brought them into conflict with man’s summertime beach activities, and this species has been driven close to extinction. As man’s beach-loving activities increase, many nests are destroyed by pets, off-road vehicles and other forms of disturbance.

 

Another beach nester, now endangered in some areas, is the Black Skimmer. These birds prefer open beaches and sandbars, making them vulnerable to human disturbance. Reproductive success is reduced by even slight human disturbance. These magnificent birds, with their ability to flawlessly skim the surface even in high winds over rough seas, have written their own chapter into the annals of flight. There are only three species of skimmers in the world. It would be a tragedy indeed if future generations lost the opportunity to witness this unique spectacle.

 

Black Skimmers
Figure 11 - Black Skimmers

Laughing Gulls Mate
Figure 12 - Laughing Gulls Mate

The lengthening days of spring, and the abundance of food, signals the time to renew life. These Laughing Gulls will soon be raising a brood.

We have within our grasp the knowledge and the ability to preserve these interesting creatures that share our planet. Many are now working toward that end. Whether or not enough of us have the will to exercise this knowledge as good stewards of our world awaits to be seen. Those of us alive today may not know if our efforts were adequate, but future generations will know how we did.

 

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