Large numbers of northbound shorebirds stopover at Delaware Bay during spring migration on their way from South American wintering areas to arctic breeding grounds. Their migration coincides with the spawning of the horseshoe crabs, whose eggs constitute the bulk of the shorebird diet, allowing them to refuel to complete the 4,000+ mile journey to their arctic breeding grounds. In recent years, horseshoe crab and shorebird populations have experienced significant declines, and there is strong evidence that these shorebird declines are related to the decreased availability of horseshoe crab eggs. Other anthropogenic factors such as exposure to contaminants may also be impacting the shorebird populations.
Contaminant exposure can have negative effects on reproduction, egg hatchability, hatchling and adult survivorship, and neurobehavior. In 2011 and 2012, scientists from NJ Audubon (Nellie Tsipoura) and Rutgers University (Joanna Burger) have been conducting research on metal levels in Semipalmated Sandpiper, Sanderling, and Red Knot. Working closely with other shorebird scientists, they have collected blood and feathers from these shorebirds along the Delaware Bay shore of Cumberland and Cape May counties during the month of May. Samples are being analyzed at Rutgers University to determine levels of lead, mercury, and other contaminants.