Friday, January 18, 2008

Tierra del Fuego: 1/18/08

Our Seventh Expedition to Tierra del Fuego: 1/18/08

Guy Morrison and Ken Ross carried out their recount but found no more knots than on their first aerial count of the bay. They plan to fly a third time to confirm the count but already it seems certain that the red knot population in Bahia Lomas has fallen by a further 30% over the past year. It’s premature to ask why, but along with declines in other wintering areas, it appears that the red knot population may be in greater danger than it was only a year ago.

In 2004, a paper published in the Proceedings of the Royal Society in Britain projected that the rufa subspecies of the red knot could become extinct by 2010. Stable numbers over the past few years have suggested that this prediction was unduly pessimistic. In light of this year’s surveys, however, extinction within a very few years seems quite possible. We will know more by the end of the expedition.

Tierra del Fuego

Our work goes well. On Tuesday the 15th we set our net at a new site half way between our old camp along the extensive flats on the west side of the bay and Punta Espora where the Straits of Magellan become narrow. We named the site the Twin Hills minefield after the two small hills that bookend a fenced-off active minefield that borders the beach. The site had great promise (as long as we didn’t attempt to cross the fence!). Guy Morrison and Ken Ross saw knots and godwits there on their Sunday aerial survey flight and we found similar numbers on Monday, but on that occasion we arrived too late to set the cannon net so we decided to attempt a catch there on Tuesday.

Tierra del Fuego

(Sign marking mine field behind beach at Twin Hills mine site)

Four peninsulas of rock projecting into the sea make it a perfect roosting site for knots, Hudsonian godwits and Magellanic oystercatchers. A steep beach makes for easier cannon netting because the tide heights are much less difficult to predict than the almost imperceptible slope of the flats across the rest of Bahia Lomas. Using a technique developed by Clive Minton we established the likely level of the next high tide compared with the previous one. It requires two people, one at the old tide line, the other marking a point on their leg equal to the difference in the tides. In this case it was 6 inches. The person at the old tide line must lie down so that one eye is almost on the ground and direct the other person to move closer or further away until the mark on their leg aligns with the horizon beyond. At that point the person stands at the estimated new high tide line.

Tierra del Fuego

(Magellanic Oystercatchers and behind them Hudsonian Godwits on the Twin Hills site.)

The team set the net and after some difficulty we caught 90 birds, of which 36 were knots. We caught 50 white-rumped sandpipers and four Hudsonian godwits. The SAG and USDA staff joined us and our processing went fast and well.

Tierra del Fuego

(Mike from USDA and Julisa from SAG samping a white rump for Avian Flu)

Tierra del Fuego

(Claudio from Wildlife Conservation Society and Daniel from SAG sampling birds for Avian Flu)

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(Antonia daughter of Carmne Espoz holding a hudsonian godwit)

The next day a ferocious wind descended on the area. Gauges on the ferry at the narrows clocked hurricane force winds of over 70 miles/hour. Needless to say the wind narrowed our options considerably. In the end we decided to abandon an attempt to catch and spent time at base camp preparing for the following day.

Tierra del Fuego

(Mist net blown by wind storm on Bahia Lomas.)

The next day, Thursday, the winds had fallen to a still considerable 30+ mph, a speed that would rule out netting in most places. We decided to go back to the Twin Hills minefield because the roost was in the lee of the hills and the winds, though gusty, would not be a problem. The knots did show up, but soon left, and we were forced to go on to plan B. A flock of over 500 Magellanic Oystercatchers roosted at the site and there was no better time to go after them. After a brilliant “twinkle” by Humphrey and Ricardo, we had 85 oystercatchers in the net. With their bright orange-red bills, yellow eyes and pied plumage, they are marvelous birds in the hand. We soon discovered that they must also be remarkably tough because several had old injuries or deformities that they had obviously learned to live with. One had a foot missing; another had elongated and crossed mandibles; another’s bill bent to the right. In the field, the Magellanic oystercatcher’s call seems high-pitched and thin, but when some of the birds objected to being handled, their calls were ear-splitting. We all enjoyed the experience of getting up-close and personal with such a striking and charismatic species.

Tierra del Fuego

(Camouflage net on at the Twin Hills site)

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(Humphrey holding a Magellanic Oystercatcher.)

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(Ricardo, Mandy and Gabriella processing oystercatchers)

Tierra del Fuego

(David holding a Magellanic Oystercatcher.)

Previous entries for this expedition: 1/14/08


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