Expedition to Tierra del Fuego – February 7, 2001
Ricardo and Olivia left the Estancia to meet the landowner from whom we needed permission. We learned the previous night through a satellite phone call that Jorge Jordan had spoke to him so we were somewhat optimistic about our chances. While Ricardo and Olivia were gone, we reluctantly bid farewell to Guy, Rick and Ken. They planned to leave early for various reasons. Guy said it was like leaving in the middle of a movie. We were sorry to see them go.
Together we had learned that studying the birds of Bahia Lomas, although a worthwhile effort, required a great deal of field biology 101. Even though this may be one of the most important shorebird wintering areas in the world, no one has really tried to understand the behavior and habitat ecology of these birds. As we carried out our work we not only learned about the bay and the birds but we uncovered more of what we don’t know.
Ricardo arrived with the permission we sought. Within an hour of his return we rolled out of the Estancia with two full trucks of equipment and personal gear. We planned to spend the night in the western access point, first to observe the distribution of birds and then to try to mist net. We knew we faced significant odds, but we didn’t appreciate the depth of our ignorance.
On arrival we set up four mist nets, for no other reason than to lay down a system. Mist netting has to be done at night for Red Knots and among shorebirds they stand out as wary and difficult to trap. Before we came to Terra Del Fuego, we invited Thunis Piersma of the Netherlands Sea Institute, Brian Harrington of Manomet Bird Observatory, and Guy to a conference call on trapping the red knot with mist nets. Thunis captures knots using mist nets on the Waddensea in the Netherlands, Guy on James Bay in the Canadian Arctic and Brian in various places on the flyway. It was a conversation any wildlife biologist would appreciate. Basically, we could trap in two ways. The first, done in the Waddensea and James Bay relied on a continuous line of mist nets, up to 50 at 12 meters each, stretched across an area of regular movement, between roost and feeding areas, for example. The second, presented by Brian, required more stealth. Biologists with four nets would approach a nighttime roost or feeding flock and position them in a right angle upwind or towards the moon from the flock. Then he would flush the flock into the net.
We had hoped to use cannon nets like we do on the Delaware Bay. With cannon nets you locate a flock, sets a net parallel to the beach on either side then move the birds towards the front of the net. You can tell a Brit perfected the method; moving the birds is called twinkling, keeping them out of the danger zone is called jiggling. That Brit, now an Australian, Clive Minton comes to the Delaware Bay each spring to lead our banding team. Cannon netting is more predicable and more often successful. But on Bahia Lomas the knots spread out across the beachfront in thin feeding groups broken by long areas of empty beach. We felt that mist nets gave us the best chance.
We intended to set our nets just after the high tide which occurred at about 9:00 p.m. About six to seven thousand knots foraged out on the flooding tide flat and we took shifts watching them for changes in distribution. The bay would flood about a half a meter higher than yesterday so we expected some change. But at about 7:30, two hours before high tide, all the birds lifted off and flew to the east. Without an ATV we stood helpless. Ricardo and I raced off in the van to the eastern access about 5 miles down the beach but we could see little in the disappearing light.
On top of this, Brad informed us over the radio the tide flooded the beach with a vengeance, racing across the flats covering much of the upper as yet unflooded beach. The birds had to leave, otherwise they would have been forced to roost close to the headland full of roaming Patagonian foxes or attempt to forage along a advancing tide line over a substrate that could not possibly hold any prey.
We pressed on guessing the birds would return with the retreating tide. We began work in an eerie darkness with no wind, probably the stillest night we’ve experience since we’ve been here. The moonlight diffused through the sky by clouds that seem to thicken by the minute. Offshore we could easily see the lights and fires of the oil platforms. We set 20 nets, walking in a thin film of water, the remnant of the retreating tide. In the west we saw what looked like fog, approaching fast, but still indistinct and a little threatening. Within minutes, just as we opened the last net, a violent wind engulfed us bowing the nets in deep arcs, and howling fiercely. In one moment we had to rush down the net line closing the nets and rush back to our much appreciate tent.
Two hours later at 3:30 a.m., Mandy, Ricardo and I awoke to a balmy night, with a clear view of a full moon. The tide once again was rising but still low so we rushed out to open our nets before sunrise. At the last net we heard a large flock of knots working a nearby flat. Within a few minutes Brad, Sherry and Bruno joined us and we were marching towards the flock with a four net set. But the darkness faded from a slow rising sun and as we approached the flock got wise and flew off.
The day hadn’t yet ended however. The tide once again marched across the flat going high at about 1000 and once again we watched several flocks join and fly off into the east horizon, leaving us alone on a fast flooding flat. We have to find the roost.
Lawrence J. Niles, PhD
Chief, NJ Endangered Species Program