Shorebirds and Horseshoe Crab Studies on Delaware Bay 2024 – Part 1

Larry Niles – May 13, 2024

This week, Susan Linder and her team surveyed horseshoe crab egg densities on all the Delaware Bay beaches along the Cape May Peninsula. They found the densities of egg clusters equal to the seasonal high of the last few years – two weeks earlier than usual.  This is excellent news for the many semipalmated sandpipers, dunlin and short-billed dowitchers that arrived in early May and the red knots, ruddy turnstones and sanderlings just now arriving.

Peak horseshoe crab egg cluster densities from 2015-2023 averaging all beaches compared to cluster density this week.

What does the early spawn mean?

The short answer is it is too early to tell, but one thing is clear: this year will likely differ from all the previous years of our 28 years of research and protection.

Most of the fundamentals of the stopover will be the same. The agencies are still allowing the killing of nearly a million Delaware Bay crabs for bait and blood.

Why is a big question?

Indeed, the prey caught with the crab bait, American eels, and two species of the whelk are in a difficult state. Eels were once proposed for federal listing, and the whelk population is rapidly declining in size, a key indicator of overharvest. Multinational companies are still bleeding crabs for biochemical lysate, which until recently was seen as essential to keep the world drug supply safe from contamination. Today, it is starting to be replaced by a synthetic that is both cheaper and has great potential to be much more effective because it is manufactured, sustainable, and not sucked out of an overharvested wild animal.

What happens to the world’s supply of injectable medicines and vaccines if there is an oil spill in Delaware Bay? Agencies avoid these questions in their policy choices.

An oil tanker moving down the Delaware Bay channel. There are 5 refineries on the river in the port of Philadelphia.

Meanwhile, the horseshoe crab egg densities on the bay remain too low to support a restoration of the shorebird stopover. Whenever the peak of spawning occurs, it will likely be a fraction of the densities we saw before the overharvest. Worse, the peak of egg density comes and goes in a flash, unlike in the past when egg density remained high all through May and early June. No matter when they arrived then, they were sure to build weight and move on. Now, in the years when the crab spawn is early or late, shorebirds could miss the spawn altogether.

The abundant early spawn of this year could be a sign of greater abundance. Or it could be the usual spike coming early. We can only wait and see.

But all that is background for the next three weeks. For the 28th year, our team will study both birds and crabs. We will do our best to catch red knots, ruddy turnstones and sanderlings, assess their condition, and tag them with bands, flags, and 30 satellite transmitters purchased with funding from a variety of sources including the Environment Canada.

Stephanie Feigin attaches a satellite transmitter to red knot.

This year, we will also begin a pilot project using acoustic transmitters to track horseshoe crabs from spawning areas to the ocean. If successful, we plan to conduct a full investigation next year to help define areas important to crabs both in the bay and outside on the continental shelf. The project is possible because of receivers scattered throughout the bay by the Division of Fish and Wildlife and other organizations.

Also, this year, we are collaborating with Citizens United to Protect the Maurice River to field volunteers in a new effort to protect shorebirds from disturbance. This effort will add to an existing effort conducted by Larissa Smith of Conserve Wildlife Foundation. Dr. Joanna Burger will lead the effort to implement new methods based on her two-year study of bird protection on the bay.

An aerial view of Egg Island Marsh on Delaware Bay. Egg Island is a remote marsh inaccessible from land and home of one of the largest staging areas for red knots in the east coast of the US.

Humphrey Sitters and his daughter Phillipa arrived this week. Humphrey belongs to a rapidly diminishing group, those of us who have come to the bay for the entire 28 years of our project, one of the longest bird investigations in the world. As we drove down the Bayshore road, I realized that although the bay’s resources are taxed to the extreme, the Bayshore remains one of the wildest places in the mid-Atlantic. It’s a little-known achievement of all the people at the NJ Division of Fish and Wildlife, NJ DEP, and the state’s many conservation groups that had the foresight to protect the Bayshore for the public and wildlife.

That hard work pays off now and creates a solid platform for restoring horseshoe crabs and the stopover.

Red Knots at East Point