ALL CREATURES GREAT AND SMALL

 

Some of you know by now that I am an amateur birder – I think I’ll probably always be an amateur, because there is no end to the learning in this field. One of the greatest challenges and delights for birders is the identification of shorebirds, although I’m beginning to see that it’s not as difficult as it once seemed. It takes time, experience and a friend who knows them well going with you often.

Before we get into the specific topic of red knots and horseshoe crabs, some words about migration. It is one of the true mysteries and miracles of nature. If you haven’t seen the documentary film "Winged Migration" yet, please proceed at once to wherever you obtain your DVDs or videos for home viewing, bring it home and watch it. Invite your kids to watch it with you. It will show you what I’m talking about. Seldom do I feel that a film is a life-changing experience. For me, this one was.

There are two yearly migrations, in spring and in fall. It’s the spring northbound journey I’m looking at here. This is a hurried trip: millions of shorebirds driven by hormonal urges fly nonstop for forty to eighty hours at a time, at speeds well over forty miles an hour, at altitudes of 18, 000 feet, for thousands of miles until they reach their summer breeding grounds. On this journey north the birds depend on staging areas to survive. Staging areas are food-rich stopover areas where the birds gather for several days to two weeks and ravenously feed, depositing layers of fat that fuel the next leg of their journey.

I am currently living near one of the eight major staging areas for migratory shorebirds in the United States: the Delaware Bay. Delaware and New Jersey are important staging areas for many shorebirds, and, because of that, important birding sites for serious and amateur birders from around the world. The food that provides this rest stop for the birds? Freshly-laid eggs of the horseshoe crab.

So, now we come to the red knots and the horseshoe crabs, as I promised with the pictures yesterday. The mysteries and miracles of nature are all tightly interwoven, something we humans often neglect to take into consideration. Thus, the fact that the spring shorebird migration takes place at the same time as the mating and egg-laying of the Limulus Polyphemus, the horseshoe crab. This creature is all on its own one of nature’s miracles. Older than the dinosaurs, it is a member of the group Arthropod, and has more in common with spiders and scorpions than with crabs. They congregate along the DE Bay in late April, early May. The female swims to shore with a male in tow. She scratches a shallow hole in the sand and deposits thousands of eggs. The male send out a jet of sperm to fertilize the nest. The eggs of this primitive-looking armored creature are full of fats and lipids, the very food the birds need for their long-distance flight.

Red knots fly from the tip of South America to our Bay beaches, a 4,500 mile trip. It takes the birds about the same amount of time it would take to drive from Lewes, on the DE coast, to Los Angeles. They make this trip without any staging areas, short stops to rest only. By the time they reach our shores, usually in mid-May, they are very thin and hungry. (I’d be pretty hungry if I drove from Lewes to LA without eating, I’m quite sure. Although I would have expended very little energy, so I wouldn’t be much thinner. If you watch Winged Migration you will vividly see the energy it takes to beat those wings. Think of running from Lewes to LA w/out eating! ) They eat and rest for ten days to two weeks, and at the end of this time have more than doubled their body weight.

Red knots (Calidris Canutus) are short-necked, stocky shorebirds who breed in the high arctic regions. The North American birds nest and breed in Alaska and far northern Canada after making their amazing flight north. Here at the Delaware Bay staging grounds scientists from all over the world are studying the red knot population, as they also are in Tierra del Fuego, Argentina. In both places the population has sharply declined. In Argentina in 2000, 52,000 red knots were observed. Two years later, the number dropped to 26,000.

Many other shorebird species stop at this staging ground, but the redknot makes a good indicator of the health of all of them because it is one of the largest, has such a long migratory route and puts on such large amounts of weight here. Their decline could be an early signal of trouble for many other bird species. Scientists suspect that the main reason for the decline is the thinning of the horseshoe crab population. More than ten years ago Bill Hall, a marine education specialist at the University of DE, began to track a decline in horseshoe crabs. Hall’s Sea Grant program has a terrific website where you can learn about this truly astounding denizen of the deep. Here you will learn the many uses they have had over the years, from fertilizer on the fields in colonial times until the present times, to biomedical wonders currently. We owe most of what we know about the function of the human eye to studies of the compound eye of the horseshoe crab. The creatures also contain a substance called chitin which has wound-healing, antibacterial, tumor-inhibiting, and waste-water treatment properties. It makes me want to go back to school and start all over again as a marine biologist. (More can be found on this whole topic here.)

Their diminishing numbers have been blamed on watermen, as they are used by commercial fishermen as bait for conch, catfish and many other fish and their commercial harvests in this area have more than doubled.

Wild creatures, including birds, are losing habitat at an enormous rate all over the world. Anything that depends on coastal property for the continuation of life is in big trouble. We humans want the beaches for our condos, golf resorts, tennis clubs, marinas. We also want our livelihoods if we are commercial fishermen. If we are seafood eaters we want our blackened catfish and conch fritters, don’t we? We also want our medical miracles.

What’s the answer? There is some good news here: three years ago federal fisheries managers set up a protected thirty-square-mile sanctuary for horseshoe crabs at the mouth ofthe Delaware Bay. This year a ban was added on harvests from the water and from the shore from May through early June in Delaware and New Jersey. Officials in these two states and nearby Maryland also dramatically cut annual harvest limits. New Jersey’s Audubon Society wants the U.S. Fish and Wildlife Service to list the red knots as an endangered or a threatened species, which would force a recovery plan to be drawn up. Such a plan would affect beach replenishment, limit disturbance in feeding areas (as is now done with the plovers during nesting and breeding season), and put more controls on horseshoe crab harvests by the fishing and biomedical industries.

However, the Delaware Bay is the largest oil transfer port-of-entry on the East Coast. An oil spill of any magnitude here would be devastating to the hundreds of thousands of shorebirds dependent on the horseshoe crab eggs. We had a small one last year, a large one can always happen. The Delaware River and Bay are also growing increasingly more polluted from the industries along the banks.

The International Shorebird Survey (ISS) gathers data from both amateur and professional researchers which they supply to a number of refuges, works with governmental and conservation agencies on specific shorebird conservation issues. The Western Hemisphere Shorebird Reserve Network (WHSRN) is a voluntary collaboration of private and government organizations committed to protecting shorebirds and their wetland habitats. Wetlands for the Americas is expanding programsin South America, the wintering grounds for most of our migratory shorebirds.

You can help by supporting agencies like the Nature Conservancy, the Audubon Society, Natural Resources Defense Council with your donations. If you are a birder you can keep accurate field notes and forward your counts to the ISS. You can look for colorbanded shorebirds, try to record the complete band combination and be sure to note the color of the leg flag (Delaware’s color flag is pale green) .

Perhaps the first step in helping to save nesting, breeding and staging habitat is for all of us to become aware of how important it is. It’s why I said invite your kids to watch Winged Migration with you – you can’t start too early to foster awareness of the interconnectedness of the world around us, of the miracles and mysteries of the natural world. Ask your kids (as well as yourselves!) to ponder questions such as these raised by Arthur Morris in Shorebirds, Beautiful Beachcombers:  how does a young Pectoral Sandpiper raised in central-northern Russia find its way to Argentina? How does a baby American Golden Plover elude a hungry arctic fox? How does a driveway-raised Killdeer chick evade the wheels of the family car?

And – what does a returning Willet think when it finds that the marsh it bred in last year is now a shopping mall?

Some of the information for this article came from:
Shorebirds: Beautiful Beachcombers, by Arthur Morris  and from "Birds' decline not a good sign: Scientists converge on Delaware Bay to study links between horseshoe crabs, migratory birds" by Molly Murray, Wilmington News Journal Online, 5/26/04.