Delaware Bay Shorebirds


In the spring of 1999, I came across a call for volunteers from the New Jersey Fish and Wildlife's Endangered and Non-game Species Program (NJ ENSP); they wanted people to help with an international shorebird banding program. You see, the Delaware Bayshore—little more than a stone's throw from my house—is one of only two major locations where certain species of birds stop on their journey from "wintering" grounds in southern South America to their breeding grounds in the Arctic. Why stop here? We have the world's largest population of horseshoe crabs that lay millions of eggs during high spring our tides—just when the birds are passing through on their tight schedule and are in desperate need of food...

With recent years of heavy harvesting of horseshoe crabs for eel and whelk bait, and the continuing human development of coastal habitat, there has been great concern that a decline in horseshoe crab numbers and a loss of their nesting beaches will result in too few crab eggs being laid to feed the birds when they arrive. Not enough food means the birds can't put on weight; not enough weight means they either don't make it to the Arctic with enough energy to breed, or they might not even make it there at all. No breeding birds mean no new birds to replace the ones that die, resulting in declining populations.

Numerous local, national and international teams are in the field around the world throughout the year collecting data in order to better understand this phenomenon, what impacts it and how, how resilient the system is to natural and man-made influences (both positive and negative) and more in order that this annual spectacle is preserved.

Making a judgment call on when and where to fire a net involves much deliberation. The number of birds present, their species (there are target species and numbers established for each study period), timing of tides, surf condition, wind speed and direction are all factors that determine whether a catch should be attempted.

A group of experienced shorebird enthusiasts and avian biologists from Australia, Britain, Scotland, Brazil, Argentina, Canada, New Zealand and elsewhere have been coming here for the past years to join the NJ ENSP staff in banding these birds and collecting data in an effort to understand this amazing phenomenon, and to keep a finger on its pulse in an effort to protect both the crabs and the birds.

I became part of that team in 1999, and got out once or twice in 2000, but was able to spend more time with the project in 2001 and thereby became an "official" member. I again attended the better part of the catches in 2002.

What I still find incredible is that the shorebird team consists nearly entirely of volunteers: the international teams whose members have been ringing (non-American term for bird banding) shorebirds for decades who give of their time and use their own resources to get here (and often lend us their equipment), the folks who live within a reasonable (or sometimes not so reasonable, but they come anyway) commuting distance, even people who merely walked up to ask what the team is doing are successfully put to work.

Imagine a small-mesh net, rectangular in shape, anchored into the sand on one long edge, with a weight tied to the two corners not anchored, with these weights each being loaded into a cannon. Now fold the net back on itself and settle it into the sand. The result looks like this.

Fire the cannon and the weights fly out, carrying the net up and over the top of a flock of birds. Weights fall, net falls, birds are harmlessly caught under the net.

That's the bare bones of cannon netting. It takes much finesse to do it successfully.

Let me see if I can give you an overview...

The birds—this study* dealing primarily with red knot, ruddy turnstone, and sanderling—have made a non-stop flight from their first lay-over in Brazil after having traveled north from Argentina. They arrive in NJ and DE beginning in early May at or even below their normal body weight. Here they gorge nearly continuously on horseshoe crab eggs, which the crabs are laying in nests dug in the beach above the high spring tide line. Goodly amounts of the eggs are found at or near the surface of the sand due to surf action stirring up nests too close to the water or from crabs digging up other nests when they dig their own; this is what the birds feed on, the extras or “overspill”, not eggs that will ever produce more crabs.

By feeding nearly exclusively on these eggs for roughly two weeks, many birds can double their body weight. Reaching a point where they can just barely get off the ground when it is time to continue north ensures sufficient fat reserves for the rest of the trip with enough left over for courtship, territorial defense, and egg-laying needs.

And the waiting begins. The spotters, whose decision it is to say "Fire", are watching the beach for the birds to return to the area of the net; the rest of us wait. (And wait and wait and wait...)

Many, many thanks are owed to local residents who let us work from their properties.

By trapping birds and banding them through the period between May and June's full moons (the main time nowadays for the majority of the crab nesting), the weights of these birds can be tracked, as well as the amount of time they spend here, locations where they are foraging, roosting, etc. Correlated with things like crab counts and egg densities, weather systems, beach disturbance, and so on, a broad overview of the ecology of the phenomenon can be drawn.

Getting the birds in hand is at once simple and complex. Many years of experience allows the team to pick likely trapping sites based upon the birds' location, tides, wind, and so on. Once a decision is made as to the beach for the catch, a large net similar to fish net is set up on the beach. Small cannon at each end of the net are attached to projectiles attached to the net that will lift the net up and over a flock of birds in the catching area when the cannons are fired. The team sets the net, hides off the beach, and waits until birds are safely within the range of the net. This wait could last anywhere from less than 20 minutes to four hours (or more)...

Extracting birds from the net involves the entire team. The net is lifted to allow the birds to run up away from the water, where they are screened from the sun (the dark cloth).

The net is then carefully lifted and the birds are moved to burlap holding pens.

Once birds are in range and the order to fire has been given, the team races to the beach to ensure the safety of the birds now (hopefully) in the net. All of the captured birds of the study species are removed from under the net and placed in holding pens; any gulls or other non-study species are released upon removal.

The shorebirds are then "processed" one by one. A US Fish and Wildlife metal band with a unique number (think social security #) is attached to the upper right leg of every bird; this number will allow that individual to be tracked and information about it to be logged every time it is recaptured. Weights are recorded, along with other information such as sex, breeding plumage condition, stage of molt, age and so on depending on what can be determined per species, the focus of the study, and available time (the more birds caught, the less data is collected in order to release the birds as quickly as possible).

Next, the birds are color flagged with certain combinations of colored plastic bands that indicate (1) the country where the bird was caught, (2) the location within that country - in the case of the DE Bay, whether it was on the NJ or DE side, (3) the year, and sometimes even (4) the week. These bands can be seen from a distance and allow the birds to be tracked and data collected (whether the birds switch sides of the Bay, and how long they stay at the DE Bay, for instance) without having to recapture the bird. Beginning in 2002, all newly captured red knot are banded with a unique combination of bands and flags per bird that allow specific individuals to be identified in the field.

Depending on the resources available from year to year, radio transmitters and/or geo-locators are also applied. The first radio transmitters that were attached to red knot were used to track the birds to their exact breeding grounds in the Artic, locations that had been unknown up until then.

A recaptured ruddy turnstone.

This bird was color banded in New Jersey (green band) during the first week (orange band) of the 2000 season (white band).

The color tags in the containers are for unbanded birds captured in NJ during the first week of the 2001 season. (Note the blue instead of white bands.) Since this bird already has a metal USFW band and color bands, it will not receive any more this year but 2001 data will be recorded for it, which will then be added to its "dossier".

Any bird already sporting bands and flags will go through the same process (but will not receive new bands), and the original place and date of capture, as well as any information collected then, can be looked up by means of the metal band number.

Once all information on each bird is collected, the birds are released.

Most birds fly away immediately when they are released, and after a good shake of their feathers or a bath, return to feeding—often along the same beach where the team is working. Every now and then, though, a bird is not quite sure if it is safe to fly away...

Just call me the Turnstone Whisperer! I have had two or three stay in hand after they were free to leave. After pausing for a few photo opportunities along the way, I took this bird to an unoccupied (by humans) stretch of the beach, set it down and walked away; it was gone when I turned around to look back.

[Last updated January 19, 2013.]

* New Jersey Audubon’s Research Department has spent nearly the same number of years similarly studying the Semi-palmated Sandpiper.

DELAWARE BAYSHORE SHOREBIRD PROJECT. The official page for ENSP; follow the links therein to get to specific project summaries.

BIRD BANDING LABORATORY. All about bird banding in the USA.

All photos ©ALG 2001, except the Turnstone Whisperer ©Larry Niles 2001.