Expedition to Tierra del Fuego – February 6, 2001
Our luck changed like the tides of Bahia Lomas. Our day started with a dawn survey of the bay front, west of yesterday’s survey area. We fielded eight biologists (Guy, Bruno, Sherry, Mandy, Rick, Brad, Bruce and myself) spread over about two miles of beach. We used handheld radio to report bird numbers and movements as the tide gradually receded after flooding. Within minutes, everyone reported large numbers of knots, especially in the western most edge near the headland that juts into the bay. In that area, we found that the birds lingered in the gradually draining tidal depressions for at least three hours after high tide.
We saw many banded birds, mostly from Delaware Bay and Argentina. In a process called scanning, or counting birds one by one while looking for bands, we found 54 banded birds of the 1,477 scanned. Forty of the birds came from the Delaware Bay and 9 from Argentina with the rest of unknown origin. We probably saw a total of 8,000 birds.
All together it added up to a favorable situation for capturing birds. We found in our satellite mapping two inter-tidal beaches on Bahia Lomas. The first floods with every tide, twice a day, the second closer to the headlands, floods only at the highest tides of the full and new moon. The full moon beach spreads to about two miles wide so we would have to cross it every time we wanted to trap the daily flooded beach, where the birds feed each day and night. Fortunately, the full moon beach gradually narrows as you go west so the intertidal beach lies closed to the headlands. Without the ATV, we need to set the nets close to the headlands, close to our tent where we will band the birds.
Unfortunately we still had no access to the beach. The truck nearly bogged down at one point along the beach so we had to find a western access. As covered earlier, the landowner had locked the gates of this area and the farm manager would only allow us to enter if he could lock the gate behind us. We would have to be locked in for days, a complicated prospect given that Steven Brown had fallen ill with a severe flu that has keep him in bed. We will try to meet the landowner tomorrow.
A new member joined our team today, Olivia Blank, a small-animal veterinarian in Punta Arenas, who also collaborates on several Antarctic wildlife investigations. She currently conducts animal health and contaminants studies on Penguins and Antarctic Fur Seals.
Ken Ross and Guy Morrison finalized the red knot count done at the start of the trip. It was worse than they first estimated. The count had fallen from 45,150 in 2000 to 26,335, a drop of over 18,815 birds. The great decrease in the number of birds complicates our effort to band them.
But more importantly, the drop suggests a serious change. Luis Venegas reported to us yesterday that his count in San Sebastian has remained similar to last year. So the drop was not a consequence of the birds moving to San Sebastian, and our count included all previously used areas on the Straits of Magellan. Moreover, Guy and Ken each kept separate tallies that corresponded closely, so the drop wasn’t a bias in the count. In other words, the numbers are accurate. We can only speculate on the drastic decline. But it is fair to say we came to evaluate the condition of the red knot population by counting their most important wintering area. The decline does not bode well for the red knot.
Lawrence J. Niles, PhD
Chief, NJ Endangered Species Program