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Conservation IssuesBird Banding At Delaware Bay
Dan Longhi

Bird Banding At Delaware Bay
Dan Longhi

Red knots (Calidris canutus) travel ten-thousand miles from Tierra del Fuego to the Arctic to breed. A stop at the Delaware Bay to feed on horseshoe crab eggs allows them to regain 100 grams or so they lose on the way. That is about half their pre-migration weight.

As the red knots and a swarm of thousands of other waders arrive in the Delaware Bay, a team of international biologists has also traveled thousands of miles to intercept and study them. Upon my arrival at Reed's Beach, Cape May County, May 12, 2004, I encountered the team assembled to collect data on the migrant wading birds. I expected a bunch of people from New Jersey, which there was. But there were also three people from Great Britain, two from Australia, a Dutchman, a New Zealander and a biologist from Argentina; many volunteers coming to New Jersey at their own expense to support bird conservation in the Delaware Bay. Larry Niles and a number of other dedicated people from New Jersey's Endangered and Non-game Species Program were, of course, there. There were local volunteers, too. There was also a team from Virginia Polytechnic Institute supporting the radio telemetry effort to track red knots during their stay in the area.

Some birds had been banded the previous day, but as we all know it's been a slow year for migrants and it had been the same for red knots so far. So the first afternoon I went out looking for them with Roger who was here from Plymouth, England . We went to the beaches at the south end of Stone Harbor. Didn't see a lot of red knots but the beaches were otherwise teeming with magnificent black skimmers, brants, various terns, plovers and sandpipers.

Back at the house in Reed's Beach we learned that there was a large enough group of red knots out at Fortescue Beach to the north to attempt a capture the next day. In the evening people sat around crunching data from previous catches and doing e-mail on the three computers, talking and socializing.

At Fortescue the next morning we prepared to net some birds. We spent hours surveying the beach for the highest concentration of red knots. I did not see quite the diversity of the previous day, but the beaches were legion and we were looking for concentration anyway. The cannon net was arranged on a tiny spit of sand exposed at low tide, at the mouth of an inlet leading from the marshes behind Fortescue. Around 11 AM a couple of people stayed out on the beach while a dozen of us hid behind a wooden sea wall. We waited. Finally when enough birds seemed to be in position we heard the blast of the two cannons. Everyone started running fast. I saw the net about fifty yards off roiling like hot oil in a frying pan from the dozens of birds underneath and could hear their various plaintive squawks and squeaks. We got there in seconds. We wanted to get to the net as quickly as possible to make sure no birds were trapped in the water where they obviously might drown. In one operation we secured the net on dry land and started collecting birds. Laughing gulls were released. I wish I had had a chance to examine one of these beautiful, precisely colored birds at leisure, but there was work to do. People were dashing back to holding cages set up back nearer the sea wall with what looked like armfuls of turnstones, dunlins, red knots and sanderlings. I found that I could manage no more than three birds at a time.

Once all the birds were segregated by species in holding cages and covered with a dark fine mesh net to calm them we started banding and collecting data. Teams worked banding and measuring each species. I assisted Larry in attaching radio transmitters to ten red knots.

The team banded 61 red knots, 85 ruddy turnstones, and 20 dunlins. Of the red knots nine were recaptures from previous years. One had been radio tagged in the summer of 2003. His radio transmitter had long since gone. The surgical epoxy holds on for a couple of months when regrowth of feathers sloughs it off.

People crunched the data that night and graphs were taped to the wall for everyone to see. The most important graph showed average weight for all red knots caught on any day for the last several years. The red knots stop at the Delaware Bay to load up on horseshoe crab eggs after their long flight from South America. They may lose half their body weight on that leg of the journey. They need to gain all that weight and some back before they can take off for the Arctic for breeding. The longer they linger at the Delaware Bay the less time they will have in the short Arctic summer and the lower their chances of fledging young before they and the young have to head south. The horseshoe crab population was decimated in 1990's by over-fishing. The red knot population dropped from some 100,000 to about 16,000. Fortunately, the horseshoe crabs are now protected in the bay. The catch is limited to 300,000 and no crabs can be caught during the spawning season, roughly the month of May.

There was some guarded optimism that night when the graphs were shown. The 61 banded red knots had the highest average weight for that time of May in several years. That could mean they were finding enough horseshoe crab eggs to bulk up on. People who had participated in the banding operation for several years thought the beaches had more crabs and eggs on them than in recent years.

Friday morning the Reed's Beach was teeming with turnstones and sanderlings. We banded and measured 65 turnstones, 81 sanderlings, and 4 red knots. For awhile I weighed sanderlings, but then someone was needed to record the data from turnstones. It was earlier in the day than when we had worked the day before. We set up underneath a house on stilts, so we had shade and away from the beach a little the flies and gnats weren't too bad. But keeping up recording the vital statistics on three or four birds simultaneously as people read off band numbers measured wings, bills and weights, is surprisingly tough work.

I welcomed the end for a time of banding that morning. Again back at the house people were at the computers, reporting back in from other activities like the radio telemetry, discussing future banding or relaxing. I had a chance to speak briefly with Argentinean biologist Patricia. She has banded and tracked red knots from Tierra Del Fuego to the Delaware Bay. The red knots have a small band in the shape of a flag with a series of letters on it. It is possible to read that code with a telescope while a bird is running around on a beach in Argentina or the Canadian Arctic or New Jersey. Patricia has done just that. She was seeing birds here in the Delaware Bay that she herself had banded in her home region of San Antonio Del Oeste.

I returned to Cape May County on May 28, 2004 to try and participate in another banding session. I found out that an aerial census indicated about 13,000 red knots in the Delaware Bay during this period. It was estimated that there had been about 30,000 in Tierra del Fuego when the team was there in January. People wondered where the rest of the birds were. There were some indications of ill-health among the birds - a high incidence of lice.

We managed to catch only 23 red knots at Fortescue that morning. From radio telemetry it was known that red knots were moving on. Four days earlier forty-eight of sixty radio-tagged red knots were still in the area. The day before only twenty-four could be found.

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Last revision: Saturday, November 06, 2004 - 10:30 PM